Part Ii., P. 479, Fig. 25): "we Have Here a Brother System, Bearing a Real

physical resemblance and strong analogy of structure to our own."

An imperfectly seen nebulous spot, discovered by Messier in 1774, appeared to present a remarkable similarity to the form of our starry stratum and the divided ring of our Milky Way.*

The Milky Way composed of nebulae does not belong to our starry stratum, but surrounds it at a great distance without being physically connected with it, passing almost in the form of a large cross through the dense nebulae of Virgo, especially in the northern wing, through Comae Berenicis, Ursa Major, Andromeda's girdle, and Pisces Boreales. It probably intersects the stellar Milky Way in Cassiopeia, and connects its dreary poles (rendered starless from the attractive forces by which stellar bodies are made to agglomerate into groups) in the least dense portion of the starry stratum.

We see from these considerations that our starry cluster, which bears traces in its projecting branches of having been subject in the course of time to various metamorphoses, and evinces a tendency to dissolve and separate, owing to secondary centers of attraction -- is surrounded by two rings, one of which, the nebulous zone, is very remote, while the other is nearer, and composed of stars alone. The latter, which we generally term the Milky Way, is composed of nebulous stars, averaging from the tenth to the eleventh degree of magnitude,* but appearing, when considered individually, of very different magnitudes, while isolated starry clusters (starry swarms) almost always exhibit throughout a character of great uniformity in magnitude and brilliancy.

In whatever part the vault of heaven has been pierced by powerful and far-penetrating telescopic instruments, stars or luminous nebulae are every where discoverable, the former, in p 152 some cases, not exceeding the twentieth or twenty-fourth degree of telescopic magnitude. A portion of the nebulous vapor would probably be found resolvable into stars by more powerful optical instruments. As the retina retains a less vivid impression of separate than of infinitely near luminous points, less strongly marked photometric relations are excited in the latter case, as Arago has recently shown.*

The definite or amorphous cosmical vapor so universally diffused, and which generates heat through condensation, probably modifies the transparency of the universal atmosphere, and diminishes that uniform intensity of light which, according to Halley and Olbers, should arise, if every point throughout the depths of space were filled by an infinite series of stars.*

The assumption of such a distribution in space is, however, at variance with observation, which shows us large starless regions of space, 'openings' in the heavens, as William Herschel terms them -- one, four degrees in width, in Scorpio, and another in Serpentarius. In the vicinity of both, near their margin, we find unresolvable nebulae, of which that on the western edge of the opening Scorpio is one of the most richly thronged of the clusters of small stars by which the firmament is adorned. Herschel ascribes these openings or starless regions to the attractive and agglomerative forcesof the marginal groups.*

"They are parts of our starry stratum," says he, with his usual graceful animation of style, "that have experienced great devastation from time." If we picture to ourselves the telescopic stars lying behind one another as a starry canopy spread over the vault of heaven, these starless regions in Scorpio and Serpentarius may, I think, be regarded as tubes through which we may look into the remotest depths of space. Other stars may certainly lie in those parts where the strata forming the canopy are interrupted, but these are unattainable by our instruments. The aspect of fiery meteors had led the ancients likewise to the idea of clefts or openings ('chasmata') in the vault of heaven. These openings were, however, only regarded as transient, while the reason of their being luminous and fiery, instead of obscure, was supposed to be owing to the p 153 translucent illuminated ether which lay beyond them.*

Derham, and even Huygens, did not appear disinclined to explain in a similar manner the mild radiance of the nebulae.*

When we compare the stars of the first magnitude, which, on an average, are certainly the nearest to us, with the non-nebulous telescopic stars, and further, when we compare the nebulous stars with unresolvable nebulae, for instance, with the nebula in Andromeda, or even with the so-called planetary nebulous vapor, a fact is made manifest to us by the consideration of the varying distances and the boundlessness of space, which shows the world of phenomena, and that which constitutes its causal reality, to be dependent upon the 'propagation of light'. The velocity of this propagation is according to Struve's most recent investigations, 166,072 geographical miles in a second, consequently almost a million of times greater than the velocity of sound. According to the measurements of Maclear, Bessel, and Struve, of the parallaxes and distances of three fixed stars of very unequal magnitudes ('a' Centauri, 16 Cygni, and 'a' Lyrae), a ray of light requires respectively 3, 9 1/4, and 12 years to reach us from these three bodies. In the short but memorable period between 1572 and 1604, from the time of Cornelius Gemma and Tycho Brahe to that of Kepler, three new stars suddenly appeared in Cassiopeia and Cygnus, and in the foot of Serpentarius. A similar phenomenon exhibited itself at intervals in 1670, in the constellation Vulpis. In recent times, even since 1837, Sir John Herschel has observed, at the Cape of Good Hope, the brilliant star [Greek symbol] in Argo increase in splendor from the second to the first magnitude.*

These events in the universe belong, however, with reference to their historical reality, to other periods of time than those in which the phenomena of light are first revealed to the inhabitants of the Earth: they reach us like the voices of the past. It has been truly said, that with our large and powerful telescopic instruments we penetrate alike through the boundaries of time and space: we measure the former through the latter, for in the course of an p 154 hour a ray of light traverses over a space of 592 millions of miles. While according to the theogony of Hesiod, the dimensions of the universe were supposed to be expressed by the time occupied by bodies in falling to the ground ("the brazen anvil was not more than nine days and nine nights in falling from heaven to earth"), the elder Herschel was of opinion* that light required almost two millions of years to pass to the Earth from the remotest luminous vapor reached by his forty-foot reflector.

Much, therefore, has vanished long before it is rendered visible to us -- much that we see was once differently arranged from what it now appears. The aspect of the starry heavens presents us with the spectacle of that which is only apparently simultaneous, and however much we may endeavor, by the aid of optical instruments, to bring the mildly-radiant vapor of nebulous masses or the faintly-glimmering starry clusters nearer, and diminish the thousands of years interposed between us and them, that serve as a criterion of their distance, it still remains more than probable, from the knowledge we possess of the velocity of the transmission of luminous rays, that the light of remote heavenly bodies presents us with the most ancient perceptible evidence of the existence of matter. It is thus that the reflective mind of man is led from simple premises to rise to those exalted heights of nature, where in the light-illumined realms of space, "myriads of worlds are bursting into life like the grass of the night."*

From the regions of celestial forms, the domain of Uranus, we will now descend to the more contracted sphere of terrestrial forces -- to the interior of the Earth itself. A mysterious chain links together both classes of phenomena. According to the ancient signification of the Titanic myth,* the powers of organic life, that is to say, the great order of nature, depend upon the combined action of heaven and earth.

If we suppose that the Earth, like all the other planets, primordially belonged, according to its origin, to the central body, the Sun, and to the solar atmosphere that has been separated into nebulous p 155 rings, the same connection with this continguous Sun, as well as with all the remote suns that shine in the firmament, is still revealed through the phenomena of light and radiating heat. The difference in the degree of these actions must not lead the physicist, in his delineation of nature, to forget the connection and the common empire of similar forces in the universe. A small fraction of telluric heat is derived from the regions of universal space in which our planetary system is moving, whose temperature (which according to Fourier, is almost equal to our mean icy polar heat) is the result of the combined radiation of all the stars. The causes that more powerfully excite the light of the Sun in the atmosphere and in the upper strata of our air, that give rise to heat-engendering electric and magnetic currents, and awaken and genially vivify the vital spark in organic structures on the earth's surface, must be reserved for the subject of our future consideration.

As we purpose for the present to confine ourselves exclusively within the telluric sphere of nature, it will be expedient to cast a preliminary glance over the relations in space of solids and fluids, the form of the Earth, its mean density, and the partial distribution of this density in the interior of our planet, its temperature and its electro-magnetic tension. From the consideration of these relations in space, and of the forces inherent in matter, we shall pass to the reaction of the interior on the exterior of our globe; and to the special consideration of a universally distributed natural power -- subterranean heat; to the phenomena of earthquakes, exhibited in unequally expanded circles of commotion, which are not referable to the action of dynamic laws alone; to the springing forth of hot wells; and, lastly, to the more powerful actions of volcanic processes. The crust of the Earth, which may scarcely have been perceptibly elevated by the sudden and repeated, or almost uninterrupted shocks by which it has been moved from below, undergoes, nevertheless, great changes in the course of centuries in the relations of the elevation of solid portions, when compared with the surface of the liquid parts, and even in the form of the bottom of the sea. In this manner simultaneous temporary or permanent fissures are opened, by which the interior of the Earth is brought in contact with the external atmosphere. Molten masses, rising from an unknown depth, flow in narrow streams along the declivity of mountains, rushing impetuously onward, or moving slowly and gently, until the fiery source is quenched in the midst of exhalations, and the lava becomes incrusted, as it were, by p 156 the solidification of its outer surface. New masses of rocks are thus formed before our eyes, while the older ones are in their turn converted into other forms by the greater or lesser agency of Platonic forces. Even where no disruption takes place the crystalline moleculres are displaced, combining to form bodies of denser texture. The water presents structures of a totally different nature, as, for instance, concretions of animal and vegetable remains, of earthy, calcareous, or aluminous precipitates, agglomerations of finely-pulverized mineral bodies, covered with layers of the silicious shields of infusoria, and with transported soils containing the bones of fossil animal forms of a more ancient world. The study of the strata which are so differently formed and arranged before our eyes, and of all that has been so variously dislocated, conforted, and upheaved, by mutual compression and volcanic force, leads the reflective observer, by simple analogies, to draw a comparison between the present and an age that has long passed. It is by a combination of actual phenomena, by an ideal enlargement of relations in space, and of the amount of active forces, that we are able to advance into the long sought and indefinitely anticipated domain of geognosy, which has only within the last half century been based on the solid foundation of scientific deduction.

It has been acutely remarked, "that notwithstanding our continual employment of large telescopes, we are less acquainted with the exterior than with the interior of other planets, excepting, perhaps, our own satellite." They have been weighed, and their volume measured; and their mass and density are becoming known with constantly-increasing exactness; thanks to the progress made in astronomical observation and calculation. Their physical character is, however, hidden in obscurity, for it is only in our own globe that we can be brought in immediate contact with all the elements of organic and inorganic creation. The diversity of the most heterogenous substances, their admixtures and metamorphoses, and the ever-changing play of the forces called into action, afford to the human mind both nourishment and enjoyment, and open an immeasurable field of observation, from which the intellectual activity of man derives a great portion of its grandeur and power. The world of perceptive phenomena is reflected in the depths of the ideal world, and the richness of nature and the mass of all that admits of classification gradually become the objects of inductive reasoning.

I would here allude to the advantage, of which I have already p 157 spoken, possessed by that portion of physical science whose origin is familiar to us, and is connected with our earthly existence. The physical description of celestial bodies from the remotely-glimmering nebulae with their suns, to the central body of our own system, is limited, as we have seen, to general conceptions of the volume and quantity of matter. No manifestation of vital activity is there presented to our senses. It is only from analogies, frequently from purely ideal combinations, that we hazard conjectures on the specific elements of matter, or on their various modifications in the different planetary bodies. But the physical knowledge of the heterogeneous nature of matter, its chemical differences, the regular forms in which its molecules combine together, whether in crystals or granules; its relations to the deflected or decomposed waves of light by which it is penetrated; to radiating, transmitted, or polarized heat; and to the brilliant or invisible, but not, on that account, less active phenomena of electro-magnetism -- all this inexhaustible treasure, by which the enjoyment of the contemplation of nature is so much heightened, is dependent on the surface of the planet which we inhabit, and more on its solid than on its liquid parts. I have already remarked how greatly the study of natural objects and forces, and the infinite diversity of the sources they open for our consideration, strengthen the mental activity, and call into action every manifestation of intellectual progress. These relations require, however, as little comment as that concatenation of causes by which particular nations are permitted to enjoy a superiority over others in the exercise of a material power derived from their command of a portion of these elementary forces of nature.

If, on the one hand, it were necessary to indicate the difference existing between the nature of our knowledge of the Earth and of that of the celestial regions and their contents, I am no less desirous, on the other hand, to draw attention to the limited boundaries of that portion of spacefrom which we derive all our knowledge of the heterogeneous character of matter. This has been somewhat inappropriately termed the Earth's crust; it includes the strata most contiguous to the upper surface of our planet, and which have been laid open before us by deep fissure-like valleys, or by the labors of man, in the bores and shafts formed by miners. These labors* do not extend beyond a vertical depth of somewhat more than 2000 feet (about one third of a geographical mile) below the p 159 level of the sea, and consequently only about 1/9800th of the Earth's radius.

The crystalline masses that have been erupted from active volcanoes, and are generally similar to the rocks on the upper surface, have come from depths which, although not accurately determined, must certainly be sixty times greater than those to which human labor has been enabled to penetrate. We are able to give in numbers the depth of the shaft where the strata of coal, after penetrating a certain way, rise again at a distance that admits of being accurately defined by measurements. These dips show that the carboniferous strata, together with the fossil organic remains which they contain, must lie, as, for instance, in Belgium, more than five or six thousand feet* below the present level p 160 of the sea, and that the calcareous and the curved strata of the Devonian basin penetrate twice that depth.

If we compare these subterranean basins with the summits of montains that have hitherto been considered as the most elevated portions of the raised crust of the Earth, we obtain a distance of 37,000 feet (about seven miles), that is, about the 1/524th of the Earth's radius. These, therefore, would be the limits of vertical depth and of the superposition of mineral strata to which geognostical inquiry could penetrate, even if the general elevation of the upper surface of the earth were equal to the height of the Dhawalagigi in the Himalaya, or of the Sorata in Bolivia. All that lies at a greater depth below the level of the sea than the shafts or the basins of which I have spoken, the limits to which man's labors have penetrated, or than the depths to which the sea has in some few instances been sounded (Sir James Ross was unable to find bottom with 27,600 feet of line), is as much unknown to us as the interior of the other planets of our solar system. We only know the mass of the whole Earth and its mean density by comparing it with the open strata, which alone are accessible to us. In the interior of the Earth, where all knowledge of its chemical and mineralogical character fails, we are again limited to as pure conjecture, as in the remotest bodies that revolve round the Sun. We can determine nothing with certainty regarding the depth at which the geological strata must be supposed to be in state of softening or of liquid fusion, of the cavities occupied by elastic vapor, of the condition of fluids when heated under an enormous pressure, or of the law of the increase p 161 of density from the upper surface to the center of the Earth.

The consideration of the increase of heat with the increase of depth toward the interior of our planet, and of the reaction of the interior on the external crust, leads us to the long series of volcanic phenomena. These elastic forces are manifested in earthquakes, eruptions of gas, hot wells, mud volcanoes and lava currents from craters of eruption and even in producing alterations in the level of the sea.*

Large plains and variously indented continents are raised or sunk, lands are separated from seas, and the ocean itself, which is permeated by hot and cold currents, coagulates at both poles, converting water into dense masses of rock, which are either stratified and fixed, or broken up into floating banks. The boundaries of sea and land, of fluids and solids, are thus variously and frequently changed. Plains have undergone oscillatory movements, being alternately elevated and depressed. After the elevation of continents, mountain chains were raised upon long fissures, mostly parallel, and in that case, probably cotemporaneous; and salt lakes and inland seas, long inhabited by the same creatures, were forcibly separated, the fossil remains of shells and zoophytes still giving evidence of their original connection. Thus, in following phenomena in their mutual dependence, we are led from the consideration of the forces acting in the interior of the Earth to those which cause eruptions on its surface, and by the pressure of elastic vapors give rise to burning streams of lava that flow from open fissures.

The same powers that raised the chains of the Andes and the Hiimalaya to the regions of perpetual snow, have occasioned new compositions and new textures in the rocky masses, and have altered the strata which had been previously deposited from fluids impregnated with organic substances. We here trace the series of formations, divided and superposed according to their age, and depending upon the changes of configuration of the surface, the dynamic relations of upheaving forces, and the chemical action of vapors issuing from the fissures.

The form and distribution of continents, that is to say, of that solid portion of the Earth's surface which is suited to the luxurious development of vegetable life, are associated by intimate connection and reciprocal action with the encircling p 162 sea in which organic life is almost entirely limited to the animal world. The liquid element is again covered by the atmosphere, an aërial ocean in which the mountain chains and high plains of the dry land rise like shoals, occasioning a variety of currents and changes of temperature, collecting vapor from the region of clouds, and distributing life and motion by the action of the streams of water which flow from their declivities.

While the geography of plants and animals depends on these intricate relations of the distribution of sea and land, the configuration of the surface, and the direction of isothermal lines (or zones of equal mean annual heat), we find that the case is totally different when we consider the human race -- the last and noblest subject in a physical description of the globe. The characteristic differences in races, and their relative numerical distribution over the Earth's surface, are conditions affected not by natural relations alone, but at the same time and specially, by the progress of civilization, and by moral and intellectual cultivation on which depends the political superiority that distinguishes national progress. Some few races, clinging, as it were, to the soil, are supplanted and ruined by the dangerous vicinity of others more civilized than themselves, until scarce a trace of their existence remains. Other races, again, not the strongest in numbers, traverse the liquid element, and thus become the first to acquire, although late, a geographical knowledge of at least the maritime lands of the whole surface of our globe, from pole to pole.

I have thus, before we enter on the individual characters of that portion of the delineation of nature which includes the sphere of telluric phenomena, shown generally in what manner the consideration of the form of the Earth and the incessant action of electro-magnetism and subterranean heat may enable us to embrace in one view the relations of horizontal expansion and elevation on the Earth's surface, the geognostic type of formations, the domain of the ocean (of the liquid portions of the Earth), the atmosphere with its meteorological processes, the geographical distribution of plants and animals, and, finally, the physical gradations of the human race, which is, exclusively and every where, susceptible of intellectual culture. This unity of contemplation presupposes a connection of phenomena according to their internal combination. A mere tabular arrangement of these facts would not fulfill the object I have proposed to myself, and would not satisfy that requirement for cosmical presentation awakened in me by the p 163 aspect of nature in my journeyings by sea and land, by the careful study of forms and forces, and by a vivid impression of the unity of nature in the midst of the most varied portions of the Earth. In the rapid advance of all branches of physical science, much that is deficient in this attempt will, perhaps, at no remote period, be corrected and rendered more perfect, for it belongs to the history of the development of knowledge that portions which have long stood isolated become gradually connected, and subject to higher laws. I only indicate the empirical path in which I and many others of similar pursuits with myself are advancing, full of expectation that, as Plato tells us Socrates once desired, "Nature may be interpreted by reason alone."*

The delineation of the principal characteristics of telluric phenomena must begin with the form of our planet and its relations in space. Here too, we may say that it is not only the mineralogical character of rocks, whether they are crystalline, granular, or densely fossiliferous, but the geometrical form of the Earth itself, which indicates the mode of its origin, and is, in fact, its history. An elliptical spheroid of revolution gives evidence of having once been a soft or fluid mass. Thus the Earth's compression constitutes one of the most ancient geognostic events, as every attentive reader of the book of nature can easily discern; and an analogous fact is presented in the case of the Moon, the perpetual direction of whose axes toward the Earth, that is to say, the increased accumulation of matter on that half of the Moon which is turned toward us, determines the relations of the periods of rotation and revolution, and is probably contemporaneous with the earliest epoch in the formative history of this satellite. The mathematical figure of the Earth is that which it would have were its surface covered entirely by water in a state of rest; and it is this assumed form to which all geodesical measurements of degrees refer. This mathematical surface is different from that true physical surface which is affected by all the accidents and inequalities of the solid parts.*

The whole figure of the Earth is determined when we know the amount of the p 164 compression at the poles and the equatorial diameter; in order, however, to obtain a perfect representation of its form it is necessary to have measurements in two directions, perpendicular to one another.

Eleven measurements of degrees (or determinations of the curvature of the Earth's surface in different parts), of which nine only belong to the present century, have made us acquainted with the size of our globe, which Pliny names "a point in the immeasurable universe."*

If these measurements do not always accord in the curvatures of different meridians under the same degree of latitude, this very circumstance speaks in favor of the exactness of the instruments and the methods employed, and of the accuracy and the fidelity to nature of these partial results. The conclusion to be drawn from the increase of forces of attraction (in the direction from the equator to the poles) with respect to the figure of a planet is dependent on the distribution of density in its interior. Newton, from theoretical principles, and perhaps likewise prompted by Cassini's discovery, previously to 1666, of the compression of Jupiter,* determined, in his immortal work, 'Philosophiae Naturalis Principia', that the compression of the Earth, as a homogeneous mass, was 1/230th.

Actual mesurements, p 165 made by the aid of new and more perfect analysis, have, however, shown that the compression of the poles of the terrestrial spheroid, when the density of the strata is regarded as increasing toward the center, is very nearly 1/300th.

Three methods have been employed to investigate the curvature of the Earth's surface, viz., measurements of degrees, oscillations of the pendulum, and observations of the inequalities in the Moon's orbit. The first is a direct geometrical and astronomical method, while in the other two we determine from accurately observed movements the amount of the forces which occasion those movements, and from these forces we arrive at the cause from whence they have originated, viz., the compression of our terrestrial spheroid. In this part of my delineation of nature, contrary to my usual practice, I have instanced methods because their accuracy affords a striking illustration of the intimate connection existing among the forms and forces of natural phenomena, and also because their application has given occasion to improvements in the exactness of instruments (as those employed in the measurements of space) in optical and chronological observations; to greater perfection in the fundamental branches of astronomy and mechanics in respect to lunar motion and to the resistance experienced by the oscillations of the pendulum; and to the discovery of new and hitherto untrodden paths of analysis. With the exception of the investigations of the parallax of stars, which led to the discovery of aberration and nutation, the history of science presents no problem in which the object attained -- the knowledge of the compression and of the irregular form of our planet -- is so far exceeded in importance by the incidental gain which has accrued, through a long and weary course of investigation, in the general furtherance and improvement of the mathematical and astronomical sciences. The comparison of eleven measurements of degrees (in which are included three extra-European, namely, the old Peruvian and two East Indian) gives, according to the most strictly theoretical requirements allowed for by Bessel,* a compression p 166 of 1/299th.

In accordance with this, the polar radius is 10,938 toises (69,944 feet), or about 11 1/2 miles, shorter than the equatorial radius of our terrestrial spheroid. The excess at the equator in consequence of the curvature of the upper surface of the globe amounts, consequently, in the direction of gravitation, to somewhat more than 4 3/7th times the height of Mont Blanc, or only 2 1/2 times the probable height of the summit of the Chawalagiri, in the Himalaya chain. The lunar inequalities (perturbation in the moon's latitude and longitude) give according to the last investigations of Laplace, almost the same result for the ellipticity as the measurements of degrees, viz., 1/299th. The results yielded by the oscillation of the pendulum give, on the whole, a much greater amount of compression, viz., 1/288th.*

Galileo, who first observed when a boy (having, probably, suffered his thoughts to wander from the service) that the height of the vaulted roof of a church might be measured by the time of the vibration of the chandeliers suspended at different altitudes, could hardly have anticipated that the pendulum would one day be carried from pole to pole, in order to determine the form of the Earth, or, rather, that the unequal density of the strata of the Earth affects the length of the seconds pendulum by means of intricate forces of local attraction, which are, however, almost regular in large tracts of land. These geognostic relations of an instrument intended for the measurement of time -- this property of the pendulum, by which, like a sounding line, it searches unknown depths, and reveals in volcanic islands,* or in the declivity of elevated continental mountain chains,** dense masses of basalt and melaphyre instead of cavities, render it difficult, notwithstanding the admirable simplicity of the method, to arrive at any great result regarding the figure of the Earth from observation of the oscillations of the pendulum.

In the astronomical part of the determination of degrees of latitude, mountain chains, or the denser strata of the Earth, likewise exercise, although in a less degree, an unfavorable influence on the measurement.

As the form of the Earth exerts a powerful influence on the motions of other cosmical bodies, and especially on that of its own neighboring satellite, a more perfect knowledge of the motion of the latter will enable us reciprocally to draw an inference regarding the figure of the Earth. Thus, as Laplace ably remarks,* "An astronomer, without leaving his observatory, may, by a comparison of lunar theory with true observations, not only be enabled to determine the form and size of the Earth, but also its distance from the Sun and Moon -- results that otherwise could only be arrived at by long and arduous expeditions to the most remote parts of both hemispheres."

p 169 The compression which may be inferred from lunar inequalities affords an advantage not yielded by individual measurements of degrees or experiments with the pendulum, since it gives a mean amount which is referable to the whole planet. The comparison of the Earth's compression with the velocity of rotation shows, further, the increase of density from the strata from the surface toward the center -- an increase which a comparison of the ratios of the axes of Jupiter and Saturn with their times of rotation likewise shows to exist in these two large planets. Thus the knowledge of the external form of planetary bodies leads us to draw conclusions regarding their internal character.

The northern and southern hemispheres appear to present nearly the same curvature under equal degrees of latitude, but, as has already been observed, pendulum experiments and measurements of degrees yield such different results for individual portions of the Earth's surface that no regular figure can be given which would reconcile all the results hitherto obtained by this method. the true figure of the Earth is to a regular figure as the uneven surfaces of water in motion are on the even surface of water at rest.

When the Earth had been measured, it still had to be weighed. The oscillations of the pendulum* and the plummet have here likewise served to determine the mean density of the Earth, either in connection with astronomical and geodetic operations, with the view of finding the deflection of the plummet from a vertical line in the vicinity of a mountain, or by a comparison of the length of the pendulum in a plain and on the summit of an elevation, or, finally, by the employment of a torsion balance, which may be considered as a horizontally vibrating pendulum for the measurement of the relative density of neighbouring strata.

Of these three methods* the p 170 last is the most certain, since it is independent of the difficult determination of the density of the mineral masses of which the spherical segment of the mountain consists near which the observations are made.

According to the most recent experiments of Reich, the result obtained is 5.44; that is to say, the mean density of the whole Earth is 5.44 times greater than tht of pure water. As according to the nature of the mineralogical strata constituting the dry continental part of the Earth's surface, the mean density of this portion scarcely amounts to 2.7, and the density of the dry and liquid surface conjointly to scarcely 1.6, it follows that the elliptical unequally compressed layers of the interior must greatly increase in density toward the center, either through pressure or owing to the heterogeneous nature of the substances. Here again we see that the vertical, as well as the horizontally vibrating pendulum, may justly be termed a geognostical instrument.

The results obtained by the employment of an instrument of this kind have led celebrated physicists, according to the difference of the hypothesis from which they started, to adopt p 171 entirely opposite views regarding the nature of the interior of the globe. It has been computed at what depths liquid or even gaseous substances would, from the pressure of their own superimposed strata, attain a density exceeding that of platinum or even iridium; and in order that the compression which has been detrmined within such narrow limits might be brought into harmony with the assumption of simple and infinitely compressible matter, Leslie has ingeniously conceived the nucleus of the world to be a hollow sphere, filled with an assumed "imponderable matter, having an enormous force of expansion." These venturesome and arbitrary conjectures have given rise, in wholly unscientific circles, to still more fantastic notions. The hollow sphere has by degrees been peopled with plants and animals, and two small subterranean revolving planets -- Pluto and Proserpine -- were imaginatively supposed to shed over it their mild light; as, however, it was further imagined that an ever-uniform temperature reigned in these internal regions, the air, which was made self-luminous by compression, might well render the planets of this lower world unnecessary. Near the north pole, at 80 degrees latitude, whence the polar light emanates, was an enormous opening, through which a descent might be made into the hollow sphere, and Sir Humphrey Davy and myself were even publicly and frequently invited by Captain Symmes to enter upon this subterranean expedition: so powerful is the morbid inclination of men to fill unknown spaces with shapes of wonder, totally unmindful of the counter evidence furnished by well-attested facts and universally acknowledged natural laws. Even the celebrated Halley, at the end of the seventeenth century, hollowed out the Earth in his magnetic speculations. Men were invited to believe that a subterranean freely-rotating nucleus occasions by its position the diurnal and annual changes of magnetic declination. It has thus been attempted in our own day, with tedious solemnity, to clothe in a scientific garb the quaintly-devised fiction of the humorous Holbert.*

p 172 The figure of the Earth and the amount of solidification (density) which it has acquired are intimately connected with the forces by which it is animated, in so far, at least, as they have been excited or awakened from without, through its planetry position with reference to a luminous central body. Compression, when considered as a consequence of centrifugal force acting on a rotating mass, explains the earlier condition of fluidity of our planet. During the solidification of this fluid, which is commonly conjectured to have been gaseous and primordially heated to a very high temperature, an enormous quantity of latent heat must have been liberated. If the process of solidification began as Fourier conjectures, by radiation from the cooling surface exposed to the atmosphere, the particles near the center would have continued fluid and hot. As, after long emanation of heat from the center toward the exterior, a stable condition of the temperature of the Earth would at length be established, it has been assumed that with increasing depth the subterranean heat likewise uninterruptedly increases. The heat of the water which flows from deep borings (Artesian wells), direct experiments regarding the temperature of rocks in mines, but, above all, the volcanic activity of the Earth, shown by the flow of molten masses from open fissures, afford unquestionable evidence of this increase for very considerable depths from the upper strata. According to conclusions based certainly upon mere analogies, this increase is probably much greater toward the center.

That which has been learned by an ingenious analytic calculation, expressly perfected for this class of investigations,* p 173 regarding the motion of heat in homogeneous metallic spheroids, must be applied with much caution to the actual character of our planet, considering our present imperfect knowledge of the substances of which the Earth is composed, the difference in the capacity of heat and in the conducting power of different superimposed masses, and the chemical changes experienced by solid and liquid masses from any enormous compression.

It is with the greatest difficulty that our powers of comprehension can conceive the boundary line which divides the fluid mass of the interior from the hardened mineral masses of the external surface, or the gradual increase of the solid strata, and the condition of semi-fluidity of the earthy substances, these being conditions to which known laws of hydraulics can only apply under considerable modifications. The Sun and Moon, which cause the sea to ebb and flow, most probably also affect these subterranean depths. We may suppose that the periodic elevations and depressions of the molten mass under the already solidified strata must have caused inequalities in the vaulted surface from the force of pressure. The amount and action of such oscillations must, however, be small; and if the relative position of the attracting cosmical bodies may here also excite "spring tides," it is certainly not to these, but to more powerful internal forces, that we must ascribe the movements that shake the Earth's surface. There are groups of phenomena to whose existence it is necessary to draw attention, in order to indicate the universality of the influence of the attraction of the Sun and Moon on the external and internal conditions of the Earth, however little we may be able to determine the quantity of this influence.

According to tolerably accordant experiments in Artesian wells, it has been shown that the heat increases on an average about 1 degree for every 54.5 feet. If this increase can be reduced p 174 to arithmetical relations, it will follow, as I have already observed,* that a stratum of granite would be in a state of fusion at a depth of nearly twenty-one geographical miles, or between four and five times the elevation of the highest summit of the Hinalaya.

We must distinguish in our globe three different modes for the transmission of heat. The first is periodic, and affects the temperature of the terrestrial strata according as the heat penetrates from above downward or from below upward, being influenced by the different positions of the Sun and the seasons of the year. The second is likewise an effect of the Sun, although extremely slow: a portion of the heat that has penetrated into the equatorial regions moves in the interior of the globe toward the poles, where it escapes into the atmosphere and the remoter regions of space. The third mode of transmission is the slowest of all, and is derived from the secular cooling of the globe, and from the small portion of the primitive heat which is still being disengaged from the surface. p 175 This loss experienced by the central heat must have been very considerable in the earliest epochs of the Earth's revolutions, but within historical periods it has hardly been appreciable by our instruments. The surface of the Earth is therefore situated between the glowing heat of the inferior strata and the universal regions of space, whose temperature is probably below the freezing-point of mercury.

The periodic changes of temperature which have been occasioned on the Earth's surface by the Sun's position and by meteorological processes, are continued in its interior, although to a very inconsiderable depth. The slow conducting power of the ground diminishes this loss of heat in the winter, and is very favorable to deep-rooted trees. Points that lie at very different depths on the same vertical line attain the maximum and minimum of the imparted temperature at very different periods of time. The further they are removed from the surface, the smaller is this difference between the extremes. In the latitudes of our temperate zone (between 48 degrees and 52 degrees), the stratum of invariable temperature is at a depth of from 59 to 64 feet, and at half that depth the oscillations of the thermometer, from the influence of the seasons, scarcely amount to half a degree. In tropical climates this invariable stratum is only one foot below the surface, and this fact has been ingeniously made use of by Boussingault to obtain a convenient, and as he believes, certain determination of the mean temperature of the air of different places.*

This mean temperature of the air at a fixed point, or at a group of contiguous points on the surface, is to a certain degree the fundamental element of the climate and agricultural relations of a district; but the mean temperature of the whole surface is very different from that of the globe itself. The questions so often agitated, whether the mean temperature has experienced any considerable differences in the course of centuries, whether the climate of a country has deteriorated, and whether the winters have not become milder and the summers cooler, can only be answered by means of the thermometer; this instrument has, however, scarcely been invented more than two centuries and a half, and its scientific application hardly dates back 120 years. The nature and novelty of the means interpose, therefore, very narrow limits to our investigation regarding the temperature p 176 of the air. It is quite otherwise, however, with the solution of the great problem of the internal heat of the whole Earth. As we may judge of uniformity of temperature from the unaltered time of vibration of a pendulum, so we may also learn, from the unaltered rotatory velocity of the Earth, the amount of stability in the mean temperature of our globe. This insight into the relations between the 'length of the day' and the 'heat of the Earth' is the result of one of the most brilliant applications of the knowledge we had long possessed of the planet. The rotatory velocity of the Earth depends on its volume; and since, by the gradual cooling of the mass by radiation, the axis of rotation would become shorter, the rotatory velocity would necessarily increase, and the length of the day diminish, with a decrease of the temperature. From the comparison of the secular inequalities in the motions of the Moon with the eclipses observed in ancient times, it follows that, since the time of Hipparchus, that is, for full 2000 years, the length of the day has certainly not diminished by the hundredth part of a second. The decrease of the mean heat of the globe during a period of 2000 years has not, therefore, taking the extremest limits, diminished as much as 1/306th of a degree of Fahrenheit.*

This invariability of form presupposes also a great invariability in the distribution of relations of density in the interior of the globe. The translatory movements, which occasion the eruptions of our present volcanoes and of ferruginous lava, and the filling up of previously empty fissures and cavities with dense masses of stone, are consequently only to be regarded as slight superficial phenomena affecting merely one portion of the Earth's crust, which, from their smallness when compared to the Earth's radius, become wholly insignificant.

I have described the internal heat of our planet, both with reference to its cause and distribution, almost solely from the results of Fourier's admirable investigations. Poisson doubts the fact of the uninterrupted increase of the Earth's heat p 177 from the surface to the center, and is of opinion that all heat has penetrated from without inward, and that the temperature of the globe depends upon the very high or very low temperature of the regions of space through which the solar temperature of the regions of space, through which the solar system has moved. This hypothesis, imagined by one of the most acute mathematicians of our time, has not satisfied physicists or geologists, or scarcely indeed any one besides its author. But, whatever may be the cause of the internal heat of our planet, and of its limited or unlimited increase in deep strata, it leads us, in this general sketch of nature, through the intimate connection of all primitive phenomena of matter, and through the common bond by which molecular forces are united, into the mysterious domain of magnetism. Changes of temperature call forth magnetic and electric currents. Terrestrial magnetism, whose main character, expressed in the three-fold manifestation of its forces, is incessant periodic variability, is ascribed either to the heated mass of the Earth itself,* or to those galvanic currents which we consider as electricity in motion, that is, electricity moving in a closed circuit.**

The mysterious course of the magnetic needle is equally affected by time and space, by the sun's course, and by changes of place on the Earth's surface. Between the tropics, the hour of the day may be known by the direction of the needle as well as by the oscillations of the barometer. It is affected instantly, but only transiently, by the distant northern light as it shoots from the pole, flashing in beams of colored light across the heavens. When the uniform horary motion of the needle is disturbed by a magnetic storm, the perturbation manifests itself 'simultaneously', in the strictest sense of the word, over hundreds and thousands of miles of sea and land, or propagates itself by degrees, in short intervals of time, in p 178 every direction over the Earth's surface.*

In the former case, the simultaneous manifestation of the storm may serve, within certain limitations, like Jupiter's satellites, fire-signals, and well-observed falls of shooting stars, for the geographical determination of degrees of longitude. We here recognize with astonishment that the perturbations of two small magnetic needles, even if suspended at great depths below the surface, can measure the distances apart at which they are placed, teaching us, for instance, how far Kasan is situated east of Gottingen or of the banks of the Seine. There are also districts in the earth where the mariner, who has been enveloped for many days in mist, without seeing either the sun or stars, and deprived of all means of determining the time, may know with certainty, from the variations in the inclination of the magnetic needle, whether he is at the north or the south of the port he is desirous of entering.*

p 179 When the needle, by its sudden disturbance in its horary course, indicates the presence of a magnetic storm, we are still unfortunately ignorant whether the seat of the disturbing cause is to be sought in the Earth itself or in the upper regions of the atmosphere. If we regard the Earth as a true magnet, we are obliged, according to the views entertained by Friedrich Gauss (the acute propounder of a generaltheory of terrestrial magnetism), to ascribe to every portion of the globe measuring one eighth of a cubic meter (or 3 7/10ths of a French cubic foot) in volume, an average amount of magnetism equal to that contained in a magnetic rod of 1 lb. weight.*

If iron and nickel, and probably, also, cobalt (but not chrome, as has long been believed),* are the only substances which become permanently magnetic, and retain polarity from a certain coerceive force, the phenomena of Arago's magnetism of rotation and of Faraday's induced currents show, on the other hand, that all telluric substances may possibly be made transitorily magnetic.

According to Faraday ('London and Edinburgh Philosophical Magazine', 1836, vol. viii., p. 178), pure cobalt is totally devoid of magnetic power. I know, however, that other celebrated chemists (Heinrich Rose and Wohler) do not admit this as absolutely certain. If out of two carefully-purified masses of cobalt totally free from nickel, one appears altogether non-magnetic (in a state of equilibrium), I think it probable that the other owes its magnetic property to a want of purity; and this opinion coincides with Faraday's view.

According to the experiments of the p 180 first-mentioned of these great physicists, water, ice, glass, and carbon affect the vibrations of the needle entirely in the same manner as mercury in the rotation experiments.*

Almost all substances show themselves to be, in a certain degree, magnetic when they are conductors, that is to say, when a current of electricity is passing through them.

Although the knowledge of the attracting power of native iron magnets or loadstones appears to be of very ancient date among the nations of the West, there is strong historical evidence in proof of the striking fact that the knowledge of the directive power of a magnetic needle and of its relation to terrestrial magnetism was peculiar to the Chinese, a people living in the extremest eastern portions of Asia. More than a thousand years before our era, in the obscure age of Codrus, and about the time of the return of the Heraclidae to the Peloponnesus, the Chinese had already magnetic carriages, on which the movable arm of the figure of a man continually pointed to the south, as a guide by which to find the way across the boundless grass plains of Tartary; nay, even in the third century of our era, therefore at least 700 years before the use of the mariner's compass in European seas, Chinese vessels navigated the Indian Ocean* under the direction of magnetic needles pointing to the south.

I have shown, in another work, what advantages this means of topographical direction, and the early knowledge and application of the magnetic needle gave the Chinese geographers over the Greeks and Romans, to whom, for instance, even the true direction of the Apennines and Pyrenees always remained unknown.*

The magnetic power of our globe is manifested on the terrestrial surface in three classes of phenomena, one of which exhibits itself in the varying intensity of the force, and the two others in the varying direction of the inclination, and in p 181 the horizontal deviation from the terrestrial meridian of the spot. Their combined action may therefore be graphically represented by three systems of lines, the 'isodynamic, isoclinic', and 'isogonic' (or those of equal force, equal inclination, and equal declination). The distances apart, and the relative positions of these moving, oscillating, and advancing curves, do not always remain the same. The total deviation (variation or declination of the magnetic needle) has not at all changed, or, at any rate, not in any appreciable degree, during a whole century, at any particular point on the Earth's surface,* as, for instance, the western part of the Antilles, or Spitzbergen.

In like manner, we observe that the isogonic curves, when they pass in their secular motion from the surface of the sea to a continent or an island of considerable extent, continue for a long time in the same position, and become inflected as they advance.

These gradual changes in the forms assumed by the lines in their translatory motions, and which so unequally modify the amount of eastern and western declination, in the course of time render it difficult to trace the transitions and analogies of forms in the graphic representations belonging to different centuries.

Each branch of a curve has its history, but this history does not reach further back among the nations of the West than the memorable epoch of the 13th of September, 1492, when the re-discoverer of the New World found a line of no variation 3 degrees west of the meridian of the island of Flores, one of the Azores.*

The whole of Europe, excepting a small p 182 part of Russia, has now a western declination, while at the close of the seventeenth century the needle first pointed due north, in London in 1657, and in Paris in 1669, there being thus a difference of twelve years, notwithstanding the small distance between these two places. In Eastern Russia, to the east of the mouth of the Volga, of Saratow, Nischni-Nowgorod, and Archangel, the easterly declination of Asia is advancing toward us. Two admirable observers, Hansteen and Adolphus Erman, have made us acquainted with the remarkable double curvature of the lines of declination in the vast region of Northern Asia; these being concave toward the pole between Obdorsk, on the Oby, and Turuchansk, and convex between the Lake of Baikal and the Gulf of Ochotsk. In this portion of the earth, in northern Asia, between the mountains of Werchojansk, Jakutsk, and the northern Korea, the isogonic lines form a remarkable closed system. This oval configuration* recurs regularly and over a great extent of the South Sea, almost as far as the meridian of Pitcairn and the group of the Marquesas Islands, between 20 degrees north and 45 degrees p 183 south lat.

One would almost be inclined to regard this singular configuration of closed, almost concentric, lines of declination as the effect of a local character of that portion of the globe; but if, in the course of centuries, these apparently isolated systems should also advance, we must suppose, as in the case of all great natural forces, that the phenomenon arises from some general cause.

The horary variations of the declination, which, although dependent upon true time, are apparently governed by the Sun, as long as it remains above the horizon, diminish in angular value with the magnetic latitude of place. Near the equator, for instance, in the island of Rawak, they scarcely amount to three or four minutes, while they are from thirteen to fourteen minutes in the middle of Europe. As in the whole northern hemisphere the north point of the needle moves from east to west on an average from 8 1/2 in the morning until 1 1/2 at mid-day, while in the southern hemisphere the same north point moves from west to east,* attention has recently been drawn, with much justice, to the fact that there must be a region of the Earth between the terrestrial and the magnetic equator where no horary deviations in the declination are to be observed.

This fourth curve, which might be called the 'curve of no motion', or, rather, 'the line of no variation of horary declination', has not yet been discovered.

The term 'magnetic poles' has been applied to those points of the Earth's surface where the horizontal power disappears, and more importance has been attached to these points than properly appertains to them;* and in like manner, the curve, where the inclination of the needle is null, has been termed the 'magnetic equator'.

The position of this line and its secular change of configuration have been made an object of careful investigation in modern times. According to the admirable work of Duperrey,* who crossed the magnetic equator six times between 1822 and 1825, the nodes of the two equators, that is to say, the two points at which the line without inclination intersects the terrestrial equator, and consequently passes from one henisphere into the other, are so unequally placed, that in 1825 the node near the island of St. Thomas, on the western p 184 coast of Africa, was 188 1/2 degrees distant from the node in the South Sea, close to the little islands of Gilbert, nearly in the meridian of the Viti group.

In the beginning of the present century, at an elevation of 11,936 feet above the level of the sea, I made an astronomical determination of the point (7 degrees 1' south lat., 48 degrees 40' west long. from Paris), where, in the interior of the New Continent, the chain of the Andes is intersected by the magnetic equator between Quito and Lima. To the west of this point, the magnetic equator continues to traverse the South Sea in the southern hemisphere, at the same time slowly drawing near the terrestrial equator. It first passes into the northern hemisphere a little before it approaches the Indian Archipelago, just touches the southern points of Asia, and enters the African continent to the west of Socotora, almost in the Straits of Bab-el-Mandeb, where it is most distant from the terrestrial equator. After intersecting the unknown regions of the interior of Africa in a southwest direction, the magnetic equator re-enters the south tropical zone in the Gulf of Guinea, and retreats so far from the terrestrial equator that it touches the Brazilian coast near Os Ilheos, north of Porto Seguro, in 15 degrees south lat. From thence to the elevated plateaux of the Cordilleras, between the silver mines of micuipampa and Caxamarca, the ancient seat of the Incas, where I observed the inclination, the line traverses the whole of South America, which in these latitudes is as much a magnetic 'terra incognita' as the interior of Africa.

The recent observations of Sabine* have shown that the node near the island of St. Thomas has moved 4 degrees from east to west between 1825 and 1837.

It would be extremely important to know whether the opposite pole, near the Gilbert Islands, in the South Sea, has aproached the meridian of the Carolinas in a westerly direction. These general remarks will be sufficient to connect the different systems of isoclinic non-parallel lines with the great phenomenon of equilibrium which is manifested in the magnetic equator. It is no small advantage, in the exposition of the laws of terrestrial magnetism, that the magnetic equator (whose oscillatory change of form and whose nodal motion exercise an influence on the inclination of the needle in the remotest districts of the world, in consequence of the altered magnetic latitudes)* should traverse the p 185 ocean throughout its whole course, excepting about one fifth, and consequently be made so much more accessible, owing to the remarkable relations in space between the sea and land, and to the means of which we are now possessed for determining with much exactness both the declination and the inclination at sea.

We have described the distribution of magnetism on the surface of our planet according to the two forms of 'declination' and 'inclination'; it now, therefore, remains for us to speak of the 'intensity of the force' which is graphically expressed by isodynamic curves (or lines of equal intensity). The investigation and measurement of this force by the oscillations of a vertical or horizontal needle have only excited a general and lively interest in its telluric relations since the beginning of the nineteenth century. The application of delicate optical and chronometrical instruments has rendered the measurement of this horizontal power susceptible of a degree of accuracy far surpassing that attained in any other magnetic determinations. The isogonic lines are the more important in their immediate application to navigation, while we find from the most recent views that isodynamic lines, especially those which indicate the horizontal force, are the most valuable elements in the theory of terrestrial magnetism.*

One of the earliest facts yielded by observation is, that the intensity of the total force increases from the equator toward the pole.*

p 186 The knowledge which we possess of the quantity of this increase, and of all the numerical relations of the law of intensity p 187 affecting the whole Earth, is especially due, since 1819, to the unwearied activity of Edward Sabine, who, after having observed the oscillations of the same needles at the American north pole, in Greenland, at Spitzbergen, and on the coasts of Guinea and Brazil, has continued to collect and arrange all the facts capable of explaining the direction of the isodynamic system in zones for a small part of South America. These lines are not parallel to lines of equal inclination (isoclinic line), and the intensity of the force is not at its minimum at the magnetic equator, as has been supposed, nor is it even equal at all parts of it. If we compare Erman's observations in the southern part of the Atlantic Ocean, where a faint zone (0.706) extends from Angola over the island of St. Helena to the Brazilian coast, with the most recent investigations of the celebrated navigator James Clark Ross, we shall find that on the surface of our planet the force increases almost in the relation of 1:3 toward the magnetic south pole, where Victoria Land extends from Cape Crozier toward the volcano Erebus, which has been raised to an elevation of 12,600 feet above the ice.*

If the intensity near the magnetic south pole p 188 be expressed by 2.052 (the unit still employed being the intensity which I discovered on the magnetic equator in Northern Peru), Sabine found it was only 1.624 at the magnetic north pole near Melville Island (70 degrees 27' north lat.), while it is 1.803 at New York, in the United States, which has almost the same latitude as Naples.

The brilliant discoveries of Oersted, Arago, and Faraday have established a more intimate connection between the electric tension of the atmosphere and the magnetic tension of our terrestrial globe. While Oestred has discovered that electricity excites magnetism in the neighborhood of the conducting body, Faraday's experiments have elicited electric currents from the liberated magnetism. Magnetism is one of the manifold forms under which electricity reveals itself. The ancient vague presentiment of the identity of electric and magnetic attraction has been verified in our own times. "When electrum (amber)," says Pliny, in the spirit of the Ionic natural philosophy of Thales,* is 'animated' by friction and heat, it will attract bark and dry leaves precisely as the loadstone attracts iron."

The same words may be found in the literature of an Asiatic nation, and occur in a eulogium on the loadstone by the Chinese physicist Kuopho.*

I observed with astonishment, p 189 on the woody banks of the Orinoco, in the sports of the natives, that the excitement of electricity by friction was known to these savage races, who occupy the very lowest place in the scale of humanity. Children may be seen to rub the dry, flat, and shining seeds or husks of a trailing plant (probably a 'Negretia') until they are able to attract threads of cotton and pieces of bamboo cane. That which thus delights the naked copper-colored Indian is calculated to awaken in our minds a deep and earnest impression. What a chasm divides the electric pastime of these savages from the discovery of a metallic conductor discharging its electric shocks, or a pile composed of many chemically-decomposing substances, or a light-engendering magnetic apparatus! In such a chasm lie buried thousands of years that compost the history of the intellectual development of mankind!

The incessant change or oscillatory motion which we discover in all magnetic phenomena, whether in those of the inclincation, declination, and intensity of these forces, according to the hours of the day and the night, and the seasons and the course of the whole year, leads us to conjecture the existence of very various and partial systems of electric currents on the surface of the Earth. Are these currents, as in Seebeck's experiments, thermo-magnetic, and excited directly from unequal distribution of heat? or should we not rather regard them as induced by the position of the Sun and by solar heat?*

Have the rotation of the planets, and the different degrees of velocity which the individual zones acquire, according to their respective distances from the equator, any influence on the distribution of magnetism? Must we seek the seat of these currents, that is to say, of the disturbed electricity, in the atmosphere, in the regions of planetary space, or in the polarity of the Sun and Moon? Galileo, in his celebrated 'Dialogo', was inclined to ascribe the parallel direction of the axis of the Earth to a magnetic point of attraction seated in universal space.

If we represent to ourselves the interior of the Earth as fused and undergoing an enormous pressure, and at a degree of temperature the amount of which we are unable to assign, p 190 we must renounce all idea of a magnetic nucleus of the Earth. All magnetism is certainly not lost until we arrive at a white heat,* and it is manifested when iron is at a dark red heat, however different, therefore, the modifications may be which are excited in substances in their molecular state, and in the coercive force depending upon that condition in experiments of this nature, there will still remain a considerable thickness of the terrestrial stratum, which might be assumed to be the seat of magnetic currents.

The old explanation of the horary variations of declination by the progressive warming of the Earth in the apparent revolution of the Sun from east to west must be limited to the uppermost surface, since thermometers sunk into the Earth, which are now being accurately observed at so many different places, show how slowly the solar heat penetrates even to the inconsiderable depth of a few feet. Moreover, the thermic condition of the surface of water, by which two thirds of our planet is covered, is not favorable to such modes of explanation, when we have reference to an immediate action and not to an effect of induction in the aërial and aqueous investment of our terrestrial globe.

In the present condition of our knowledge, it is impossible to afford a satisfactory reply to all questions regarding the ultimate physical causes of these phenomena. It is only with reference to that which presents itself in the triple manifestations of the terrestrial force, as a measurable relation of space and time, and as a stable element in the midst of change, that science has recently made such brilliant advances by the aid of the determination of mean numerical values. From Toronto in Upper Canada to the Cape of Good Hope and Van Diemen's Land, from Paris to Pekin, the Earth has been covered, since 1828, with magnetic observatories,* in which every regular p 191 or irregular manifestation of the terrestrial force is detected by uninterrupted and simultaneous observations. A variation p 192 of 1/40000th of the magnetic intensity is measured, and at certain epochs, observations are made at intervals of 2 1/2 minutes, and continued for twenty-four hours consecutively.

A great English astronomer and physicist has calculated* that the mass of observations which are in progress will accumulate in the course of three years to 1,958,000.

Never before has so noble and cheerful a spirit presided over the inquiry into the 'quantitative' relations of the laws of the phenomena of nature. We are, therefore, justified in hoping that these laws, when compared with those which govern the atmosphere and the remoter regions of space, may, by degrees, lead us to a more intimate acquaintance with the genetic conditions of magnetic phenomena. As yet we can only boast of having opened a greater number of paths which may possibly lead to an explanation of this subject. In the physical science of terrestrial p 193 magnetism, which must not be confounded with the purely mathematical branch of the study, those persons only will obtain perfect satisfaction who, as in the science of the meteorological processes of the atmosphere conveniently turn aside the practical bearing of all phenomena that can not be explained according to their own views.

Terrestrial magnetism, and the electro-dynamic forces computed by the intellectual Ampere,* stand in simultaneous and intimate connection with the terrestrial or polar light, as well as with the internal and external heat of our planet, whose magnetic poles may be considered as the poles of cold.**

The bold conjecture hazarded one hundred and twenty-eight years since by Halley,* that the Aurora Borealis was a magnetic phenomenon, has acquired empirical certainty from Faraday's brilliant discovery of the evolution of light by magnetic forces.

The northern light is preceded by premonitory signs. Thus, in the morning before the occurrence of the phenomenon, the irregular horary course of the magnetic needle generally indicates a disturbance of the equilibrium in the distribution of p 194 terrestrial magnetism.*

When this disturbance attains a great degree of intensity, the equilibrium of the distribution is restored by a discharge attended by a development of light "The Aurora* itself is, therefore, not to be regarded as an externally manifested cause of this disturbance, but rather as a result of telluric activity, manifested on the one side by the appearance of the light, and on the other by the vibrations of the magnetic needle."

The splendid appearance of colored polar light is the act of discharge, the termination of a magnetic storm, as in an electrical storm a development of light -- the flash of lightning -- indicates the restoration of the disturbed equilibrium in the distribution of the electricity. An electric storm is generally confined to a small space beyond the limits of which the condition of the atmospheric electricity remains unchanged. A magnetic storm, on the other hand, p 193 shows its influence on the course of the needle over large portions of continents, and, as Arago first discovered far from the spot where the evolution of light was visible. It is not improbable that, as heavily-charged threatening clouds, owing to frequent transitions of the atmospheric electricity to an opposite condition, are not always discharged, accompanied by lightning, so likewise magnetic storms may occasion far-extending disturbances in the horary course of the needle, without there being any positive necessity that the equilibrium of the distribution should be restored by explosion, or by the passage of luminous effusions from one of the poles to the equator, or from pole to pole.

In collecting all the individual features of the phenomenon in one general picture, we must not omit to describe the origin and course of a perfectly developed Aurora Borealis. Low down in the distant horizon, about the part of the heavens which is intersected by the magnetic meridian, the sky which was previously clear is at once overcast. A dense wall of bank of cloud seems to rise gradually higher and higher, until it attains an elevation of 8 or 10 degrees. The color of the dark segment passes into brown or violet; and stars are visible through the cloudy stratum, as when a dense smoke darkens the sky. A broad, brightly-luminous arch, first white, then yellow, encircles the dark segment; but as the brilliant arch appears subsequently to the smoky gray segment, we can not agree with Argelander in ascribing the latter to the effect of mere contrast with the bright luminous margin.*

The highest point of the arch of light is, according to accurate observations made on the subject,* not generally in the magnetic meridian itself, but from 5 degrees to 18 degrees toward the direction of the magnetic declination of the place.**

In the northern latitudes, p 196 in the immediate vicinity of the magnetic pole, the smoke-like conical segment appears less dark, and sometimes is not even seen. Where the horizontal force is the weakest, the middle of the luminous arch deviates the most from the magnetic meridian.

The luminous arch remains sometimes for hours together flashing and kindling in ever-varying undulations, before rays and streamers emanate from it, and shoot up to the zenith. The more intense the discharges of the northern light, the more bright is the play of colors, through all the varying gradations from violet and bluish white to green and crimson. Even in ordinary electricity excited by friction, the sparks are only colored in cases where the explosion is very violent after great tension. The magnetic columns of flame rise eithr singly from the luminous arch, blended with black rays similar to thick smoke, or simultaneously in many opposite points of the horizon, uniting together to torm a flickering sea of flame, whose brilliant beauty admits of no adequate description, as the luminous waves are every moment assuming new and varying forms. The intensity of this light is at times so great, that Lowenorn (on the 29th of June, 1786) recognized the coruscation of the polar light n bright sunshine. Motion renders the phenomenon more visible. Round the point in the vault of heaven which corresponds to the direction of the inclination of the needle, the beams unite together to form the so-called corona, the crown of the northern light, which encircles the summit of the heavenly canopy with a milder radiance and unflickering emanations of light. It is only in rare instances that a perfect crown or circle is formed, but on its completion the phenomenon has invariably reached its maximum, and the radiations become less frequent, shorter, and more colorless. The crown and the luminous arches break up, and the whole vault of heaven becomes covered with irregularly-scattered, broad, faint, almost ashy-gray luminous immovable patches, which in their turn disappear, leaving nothing but a trace of the dark, smoke-like segment on the horizon. There often remains nothing of the whole spectacle but a white, delicate cloud with feathery edges, or divided at equal distances into small roundish groups like cirio-cumuli.

This connection of the polar light with the most delicate cirrous clouds deserves special attention, because it shows that the electro-magnetic evolution of light is a part of a meteorological process. Terrestrial magnetism here manifests its influence p 197 on the atmosphere and on the condensation of aqueous vapor. The fleecy clouds seen in Iceland by Thienemann, and which he considered to be the northern light, have been seen in recent times by Franklin and Richardson near the American north pole, and by Admiral Wrangel on the Siberian coast of the Polar Sea. All remarked "that the Aurora flashed forth in the most vivid beams when masses of cirrous strata were hovering in the upper regions of the air, and when these were so thin that their presence could only be recognized by the formation of a halo round the moon." These clouds sometimes range themselves, even by day in a similar manner to the beams of the Aurora, and then disturb the course of the magnetic needle in the same manner as the latter. On the morning after every distinct nocturnal Aurora, the same superimposed strata of clouds have still been observed that had previously been luminous.*

The apparently converging polar zones (streaks of clouds in the direction of the magnetic meridian), which constantly occupied my attention during my journeys on the elevated plateaux of Mexico and in Northern Asia, belong probably to the same group of ciurnal phenomena.*

p 198 Southern lights have often been seen in England by the intelligent and indefatigable observer Dalton and northern lights have been observed in the southern hemisphere as far as 45 degrees latitude (as on the 14th of January, 1831). On occasions that are by no means of rare occurrence, the equilibrium at both poles has been simultaneously disturbed. I have discovered with certainty that northern polar lights have been seen within the tropics in Mexico and Peru. We must distinguish between the sphere of simultaneous visibility of the phenomenon and the zones of the Earth where it is seen almost nightly. Every observer no doubt sees a separate Aurora of his own, as he sees a separate rainbow. A great portion of the Earth simultaneously engenders these phenomena of emanations of light. Many nights may be instanced in which the phenomenon has been simultaneously observed in England and in Pennsylvania, in Rome and in Pekin. When it is stated that Auroras diminish with the decrease of latitude, the latitude must be understood to be magnetic, and as measured by its distance from the magnetic pole. In Iceland, in Greenland, Newfoundland, on the shores of the Slave Lake, and at Fort Enterprise in Northern Canada, these lights appear almost every night at certain seasons of the year, celebrating with their flashing beams, according to the mode of expression common to the inhabitants of the Shetland Isles, "a merry dance in heaven."*

While the Aurora is a phenomenon of rare occurrence in Italy, it is frequently seen in the latitude of Philadelphia (39 degrees 57'), owing to the southern position of the American nagnetic pole. In the districts which are remarkable, in the New Continent and the Siberian coasts, for the frequent occurrence of this phenomenon, there are special regions or zones of longitude in which the polar light is particularly bright and brilliant.*

The existence p 199 of local influences can not, therefore, be denied in these cases. Wrangel saw the brilliancy diminish as he left the shores of the Polar Sea, about Mischne-Kolymsk. The observations made in the North Polar expedition appear to prove that in the immediate vicinity of the magnetic pole the development of light is not in the least degree more intense or frequent than at some distance from it.

The knowledge which we at present possess of the altitude of the polar light is based on measurements which from their nature, the constant oscillation of the phenomenon of light, and the consequent uncertainty of the angle of parallax, are not deserving of much confidence. The results obtained, setting aside the older data, fluctuate between several miles and an elevation of 3000 or 4000 feet; and, in all probability, the northern lights at different times occur at very different elevations.*

The most recent observers are disposed to place the phenomenon in the region of clouds, and not on the confines of the atmosphere; and they even believe that the rays of the Aurora may be affected by winds and currents of air, if the phenomenon of light, by which alone the existence of an electro-magnetic current is appreciable, be actually connected with matrial groups of vesicles of vapor in motion, or, more correctly speaking, if light penetrate them, passing from one vesicle to another. Franklin saw near Great Bear Lake a beaming northern light, the lower side of which he thought illuminated a stratum of clouds, while, at a distance of only eighteen geographical miles, Kendal, who was on watch throughout the whole night, and never lost sight of the sky, perceived no phenomenon of light. The assertion, so frequently maintained of late, that the rays of the Aurora have been seen to shoot down to the ground between the spectator and some neighboring hill, is open to the charge of optical delusion, as in the cases of strokes of lightning or of the fall of fire-balls.

Whether the magnetic storms, whose local character we have illustrated by such remarkable examples, share noise as well as light in common with electric storms, is a question p 200 that has become difficult to answer, since implicit confidence is no longr yielded to the relations of Greenland whale-fishers and Siberian fox-hunters. Northern lights appear to have become less noisy since their occurrences have been more accurately recorded. Parry, Franklin, and Richardson, near the north pole; Thienemann in Iceland; Gieseke in Greenland; Lotur, and Bravais, near the North Cape; Wrangel and Anjou, on the coast of the Polar Sea, have together seen the Aurora thousands of times, but never heard any sound attending the phenomenon. If this negative testimony should not be deemed equivalent to the positive counter-evidence of Hearne on the mouth of the Copper River and of Henderson in Iceland, it must be remembered that, although Hood heard a noise as of quickly-moved musket-balls and a slight cracking sound during an Aurora, he also noticed the same noise on the following day, when there was no northern light to be seen; and it must not be forgotten that Wrangel and Gieseke were fully convinced that the sound they had heard was to be ascribed to the contraction of the ice and the crust of the snow on the sudden cooling of the atmosphere. The belief in a crackling sound has arisen, not among the people generally, but rather among learned travelers, because in earlier times the northern light was declared to be an effect of atmospheric electricity, on account of the luminous manifestation of the electricity in rarefied space, and the observers found it easy to hear what they wished to hear. Recent experiments with very sensitive electrometers have hitherto, contrary to the expectation generally entertained, yielded only negative results. The condition of the electricity in the atmosphere* p 291 is not found to be changed during the most intense Aurora; but, on the other hand, the three expressions of the power of terrestrial magnetism, declination, inclination and intensity, are all affected by polar light, so that in the same night, and at different periods of the magnetic development, the same end of the needle is both attracted and repelled.

The assertion made by Parry, on the strength of the data yielded by his observations in the neighborhood of the magnetic pole at Melville Island, that the Aurora did not disturb, but rather exercised a calming influence on the magnetic needle, has been satisfactorily refuted by Parry's own more exact researches,* detailed in his journal, and by the admirable observations of Richardson, Hood, and Franklin in Northern Canada, and lastly by Bravais and Lottin in Lapland.

The process of the Aurora is, as has already been observed, the restoration of a disturbed condition of equilibrium. The effect on the needle is different according to the degree of intensity of the explosion. It was only unappreciable at the gloomy winter station of Bosekop when the phenomenon of light was very faint and aptly compared to the flame which rises in the closed circuit of a voltaic pile between two points of carbon at a considerable distance apart, or, according to Fizeau, to the flame rising between a silver and a carbon point, and attracted or repelled by the magnet. This analogy certainly sets aside the necessity of assuming the existence of metallic vapors in the atmosphere, which some celebrated physicists have regarded as the substratum of the northern light.

When we apply the indefinite term 'polar light' to the luminous phenomenon which we ascribe to a galvanic current, that is to say, to the motion of electricity in a closed circuit, we merely indicate the local direction in which the evolution of light is most frequently, although by no means invariably, seen. This phenomenon derives the greater part of its importance from the fact that the Earth becomes 'self-luminous', and that as a planet, besides the light which it receives from the central body, the Sun, it shows itself capable in itself of developing light. The intensity of the terrestrial light, or, rather the luminosity which is diffused, exceeds, in cases of the brightest colored radiation toward the zenith, the light of the Moon in its first quarter. Occasionally, as on the 7th of January, 1831, printed characters could be read without difficulty. This almost uninterrupted development of light p 202 in the Earth leads us by analogy to the remarkable process exhibited in Venus. The portion of this planet which is not illumined by the Sun often shines with a phosphorescent light of its own. It is not improbable that the Moon, Jupiter, and the comets shine with an independent light, besides the reflected solar light visible through the polariscope. Without speaking of the problematical but yet ordinary mode in which the sky is illuminated, when a low cloud may be seen to shine with an uninterrupted flickering light for many minutes together, we still meet with other instances of terrestrial development of light in our atmosphere. In this category we may reckon the celebrated luminous mists seen in 1783 and 1831; the steady luminous appearance exhibited without any flickeriing in great clouds observed by Rozier and Beccaria; and lastly, as Arago* well remarks, the faint diffused light which guides the steps of the traveler in cloudy, starless, and moonless nights in autumn and winter, even when there is no snow on the ground.

As in polar light or the electro-magnetic storm, a current of brilliant and often colored light streams through the atmosphere in high latitudes, so also in the torrid zones between the tropics, the ocean simultaneously develops light over a space of many thousand square miles. Here the magical effect of light is owing to the forces of organic nature. Foaming with light, the eddying waves flash in phosphorescent sparks over the wide expanse of waters, where every scintillation is the vital manifestation of an invisible animal world. So varied are the sources of terrestrial light! Must we still suppose this light to be latent, and combined in vapors, in order to explain 'Moser's images produced at a distance' -- a discovery in which reality has hitherto manifested itself like a mere phantom of the imagination.

As the internal heat of our planet is connected on the one hand with the generation of electro-magnetic currents and the process of terrestrial light (a consequence of the magnetic storm), it, on the other hand, discloses to us the chief source of geognostic phenomena. We shall consider these in their connection with and their transition from merely dynamic disturbances, from the elevation of whole continents and mountain chains to the development and effusion of gaseous and p 203 liquid fluids, of hot mud, and of those heated and molten earths which become solidified into crystalline mineral masses. Modern geognosy, the mineral portion of terrestrial physics, has made no slight advance in having investigated this connection of phenomena. This investigation has led us away from the delusive hypothesis, by which it was customary formerly to endeavor to explain, individually every expression of force in the terrestrial globe: it shows us the connection of the occurrence of heterogeneous substances with that which only appertains to changes in space (disturbances or elevations), and groups together phenomena which at first sight appeared most heterogeneous, as thermal springs, effusion of carbonic acid and sulphurous vapor, innocuous salses (mud eruptions), and the dreadful devastation of volcanic mountains.*

In a general view of nature, all these phenomena are fused together in one sole idea of the reaction of the interior of a planet on its external surface. We thus recognize in the depths of the earth, and in the increase of temperature with the increase of depth from the surface, not only the germ of disturbing movements, but also of the gradual elevation of whole continents (as mountain chains on long fissures), of volcanic eruptions, and of the manifold production of mountains and mineral masses. The influence of this reaction of the interior on the exterior is not, however, limited to inorganic nature alone. It is highly probable that, in an earlier world, more powerful emanations of carbonic acid gas, blended with the atmosphere, must have increased the assimilation of carbon in vegetables, and that an inexhaustible supply of combustible matter (lignites and carboniferous formations) must have been thus buried in the upper strata of the earth by the revolutions attending the destruction of vast tracts of forest. We likewise perceive that the destiny of mankind is in part dependent on the formation of the external surface of the earth, the direction of mountain tracts and high lands, and on the distribution of elevated continents. It is thus granted to the inquiring mind to pass from link to link along the chain of phenomena until it reaches the period when, in the solidifying process of our planet, and in its first transition from the gaseous form to the agglomeration of matter, that portion of the inner heat of the Earth was developed, which does not belong to the action of the Sun.

This material taken from pages 204-248

COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt

Translated by E C Otte

from the 1858 Harper & Brothers edition of Cosmos, volume 1 --------------------------------------------------

p 204 In order to give a general delineation of the causal connection of geognostical phenomena, we will begin with those whose chief characteristic is dynamic, consisting in motion and in change in space. Earthquakes manifest themselves by quick and successive vertical, or horizontal, or rotatory vibrations.*

In the very considerable number of earthquakes which I have experienced in both hemispheres, alike on land and at sea, the two first-named kinds of motion have often appeared to me to occur simultaneously. The mine-like explosiion -- the vertical action from below upward -- was most strikingly manifested in the overthrow of the town of Riobamba in 1797, when the bodies of many of the inhabitants were found to have been hurled to Cullea, a hill several hundred feet in neight, and on the opposite side of the River Lican. The propagation is most generally effected by undulations in a linear direction,* with a velocity of from twenty to twenty-eight miles in a minute, but partly in circles of commotion or large ellipses, in which the vibrations are propagated with decreasing intensity from a center toward the circumference.

There are districts exposed to the action of two intersecting circles of commotion. In Northern Asia, where the Father of History,* and subsequently Theophylactus Simocatta,** described the districts of Scythia as free from earthquakes, I have observed the metalliferous portion of the Altai Mountains under the influence of a two-fold focus of commotion, the Lake of Baikal, and the volcano of the Celestial Mountain (Thianschan).***

When the circles of commotion intersect one another -- when, for instance, an elevated plain lies between two volcanoes simultaneously in a state of eruption, several wave-systems may exist together, as in fluids, and not mutually disturb one another. We may even suppose 'interference' p 205 to exist here, as in the intersecting waves of sound. The extent of the propagated waves of commotion will be increased on the upper surface of the earth, according to the general law of mechanics, by which, on the transmission of motion in elastic bodies, the stratum lying free on the one side endeavors to separate itself from the other strata.

Waves of commotion have been investigated by means of the pendulum and the seismometer* with tolerable accuracy in respect to their direction and total intensity, but by no means with reference to the internal nature of their alternations and their periodic intumescence.

In the city of Quito, which lies at the foot of a still active volcano (the Rucu Pichincha), and at an elevation of 9540 feet above the level of the sea, which has beautiful cupolas, high vaulted churches, and massive edifices of several stories, I have often been astonished that the violence of the nocturnal earthquakes so seldom causes fissures in the walls, while in the Peruvian plains oscillations apparently much less intense injure low reed cottages. The natives, who have experienced many hundred earthquakes, believe that the difference depends less upon the length or shortness of the waves, and the slowness or rapidity of the horizontal vibrations.* than on the uniformity of the motion in opposite directions.

The circling rotatory commotions are the most uncommon, but, at the same time, the most dangerous. Walls were observed to be twisted, but not thrown down; rows of trees turned from their previous parallel direction; p 206 and fields covered with different kinds of plants found to be displaced in the great earthquake of Riobamba, in the province of Quito, on the 4th of February, 1797, and in that of Calabria, between the 5th of February and the 28th of March, 1782. The phenomenon of the inversion or displacement of fields and pieces of land, by which one is made to occupy the place of another, is connected with a translatory motion or penetration of separate terrestrial strata. When I made the plan of the ruined town of Riobamba, one particular spot was pointed out to me, where all the furniture of one house had been found under the ruins of another. The loose earth had evidently moved like a fluid in currents, which must be assumed to have been directed first downward, then horizontally, and lastly upward. It was found necessary to appeal to the 'Audiencia', or Council of Justice, to decide upon the contentions that arose regarding the proprietorship of objects that had been removed to a distance of many hundred roises.

In countries where earthquakes are comparatively of much less frequent occurrence (as for instance, in Southern Europe), a very general belief prevails, although unsupported by the authority of inductive reasoning,* that a calm, an oppressive p 207 heat and a misty horizon, are always the forerunners of this phenomenon.

The fallacy of this popular opinion is not only refuted by my own experience, but likewise by the observations of all those who have lived many years in districts where, as in Cumana, Quito, Peru, and Chili, the earth is frequently and violently agitated. I have felt earthquakes in clear air and a fresh east wind, as well as in rain and thunder storms. The regularity of the horary changes in the declination of the magnetic needle and in the atmospheric pressure remained undisturbed between the tropics on the days when earthquakes occurred.*

These facts agree with the observations made by Adolph Erman (in the temperate zone, on the 8th of March, 1829) on the occasion of an earthquake at Irkutsk, near the Lake of Baikal. During the violent earthquake of Cumana, on the 4th of November, 1799, I found the declination and the intensity of the magnetic force alike unchanged, but, to my surprise, the inclination of the needle was diminished about 48 degrees.*

There was no ground to suspect an error in the calculation, and yet, in the many other earthquakes which I have experienced on the elevated plateaux of Quito and Lima, the inclination as well as the other elements of terrestrial magnetism remained always unchanged. Although, in general, the processes at work within the interior of the earth may not be announced by any meteorological phenomena or any special appearance of the sky, it is, on the contrary, not improbable, as we shall soon see, that in cases of violent earthquakes some effect may be imparted to the atmosphere, in consequence of which they can not always act in a purely dynamic manner.

p 208 During the long-continued trembling of the ground in the Piedmontese valleys of Pelis and Clusson, the greatest changes in the electric tension of the atmosphere were observed while the sky was cloudless. The intensity of the hollow noise which generally accompanies an earthquake does not increase in the same degree as the force of the oscillations. I have ascertained with certainty that the great shock of the earthquake of Riobamba (4th Feb., 1797) -- one of the most fearful phenomena recorded in the physical history of our planet -- was not accompanied by any noise whatever. The tremendous noise ('el gram ruido') which was heard below the soil of the cities of Quito and Ibarra, but not at Tacunga and Hambato, nearer the center of the motion, occurred between eighteen and twenty minutes 'after' the actual catastrophe. In the celebrated earthquake of Lima and Callao (28th of October, 1746), a noise resembling a subterranean thunder-clap was heard at Truxillo a quarter of an hour after the shock, and unaccompanied by any trembling of the ground. In like manner, long after the great earthquake in New Granada, on the 16th of November, 1827, described by Boussingault, subterranean detonations were heard in the whole valley of Cauca during twenty or thirty seconds, unattended by motion. The nature of the noise varies also very much, being either rolling, or rustling, or clanking like chains when moved, or like near thunder, as, for instance, in the city of Quito; or, lastly, clear and ringing, as if obsidian or some other vitrified masses were struck in subterranean cavities. As solid bodies are excellent conductors of sound, which is propagated in burned clay, for instance, ten or twelve times quicker than in the air, the subterranean noise may be heard at a great distance from the place where it has originated. In Caracas, in the grassy plains of Calabozo, and on the banks of the Rio Apure, which falls into the Orinoco, a tremendously loud noise, resembling thunder, was heard, unaccompanied by an earthquake, over a district of land 9200 square miles in extent, on the 30th of April, 1812, while at a distance of 632 miles to the north-east, the volcano of St. Vincent, in the small Antilles, poured forth a copious stream of lava. With respect to distance, this was as if an eruption of Vesuvius had been heard in the north of France. In the year 1744, on the great eruption of the volcano of Cotopaxi, subterranean noises, resembling the discharge of cannon, were heard in Honda, on the Magdalena River. The crater of Cotopaxi lies not only 18,000 feet higher than Honda, but these two points are separated by the colossal p 209 mountain chain of Quito, Pasto, and Popayan, no less than by numerous valleys and clefts, and they are 436 miles apart. The sound was certainly not propagated through the air, but through the earth, and at a great depth. During the violent earthquake of New Granada, in February, 1835, subterranean thunder was heard simultaneously at Popayan, Bogota, Santa Marta, and Caracas (where it continued for seven hours without any movement of the ground), in Haiti, Jamaica, and on the Lake of Nicaragua.

These phenomena of sound, when unattended by any perceptible shocks, produce a peculiarly deep impression even on persons who have lived in countries where the earth has been frequently exposed to shocks. A striking and unparalleled instance of uninterrupted subterranean noise, unaccompanied by any trace of an earthquake, is the phenomenon known in the Mexican elevated plateaux by the name of the "roaring and the subterranean thunder) ('bramidos y truenos subterraneos') of Guanaxuato.*

This celebrated and rich mountain city lies far removed from any active volcano. The noise began about midnight on the 9th of January, 1784, and continued for a month. I have been enabled to give a circumstantial p 210 description of it from the report of many witnesses, and from the documents of the municipality, of which I was allowed to make use. From the 13th to the 16th of January, it seemed to the inhabitants as if heavy clouds lay beneath their feet, from which issued alternate slow rolliing sounds and short, quick claps of thunder. The noise abated as gradually as it had begun. It was limited to a small space, and was not heard in a basaltic district at the distance of a few miles. Almost all the inhabitants, in terror, left the city, in which large masses of silver ingots were stored; but the most courageous, and those more accustomed to subterranean thunder, soon returned, in order to drive off the bands of robbers who had attempted to possess themselves of the treasures of the city. Neither on the surface of the earth, nor in mines 1600 feet in depth, was the slightest shock to be perceived. No similar noise had ever before been heard on the elevated tableland of Mexico, nor has this terrific phenomenon since occurred there. Thus clefts are opened or closed in the interior of the earth, by which waves of sound penetrate to us or are impeded in their propagation.

The activity of an igneous mountain, however terrific and picturesque the spectacle may be which it presents to our contemplation, is always limited to a very small space. It is far otherwise with earthquakes, which although scarcely perceptible to the eye, nevertheless simultaneously propagate their waves to a distance of many thousand miles. The great earthquake which destroyed the city of Lisbon on the 1st of November, 1755, and whose effects were so admirably investigated by the distinguished philosopher Emmanuel Kant, was felt in the Alps, on the coast of Sweden, in the Antilles, Antigua, Barbadoes, and Martinique; in the great Canadian Lakes, in Thuringia, in the flat country of Northern Germany, and in the small inland lakes on the shores of the Baltic.*

Remote springs were interrupted in their flow, a phenomenon attending earthquakes which had been noticed among the ancients by Demetrius the Callatian. The hot springs of Toplitz dried up, and returned, inundating every thing around, and having their waters colored with iron ocher. In Cadiz p 211 the sea rose to an elevation of sixty-four feet, while in the Antilles, where the tide usually rises only from twenty-six to twenty-eight inches, it suddenly rose above twenty feet, the water being of an inky blackness. It has been computed that on the 1st of November, 1755, a portion of the Earth's surface four times greater than that of Europe, was simultaneously shaken. As yet there is no manifestation of force known to us, including even the murderous inventions of our own race, by which a greater number of people have been killed in the short space of a few minutes: sixty thousand were destroyed in Sicily in 1693, from thirty to forty thousand in the earthquake of Riobamba in 1797, and probably five times as many in Asia Minor and Syria, under Tiberius and Justinian the elder, about the years 19 and 526.

There are instances in which the earth has been shaken for many successive days in the chain of the Andes in South America, but I am only acquainted with the following cases in which shocks that have been felt almost every hour for months together have occurred far from any volcano, as, for instance, on the eastern declivity of the Alpine chain of Mount Cenis, at Fenestrelles and Pignerol, from April, 1808; between New Madrid and Little Prairie,* north of Cincinnati in the United States of America, in December, 1811, as well as through the whole winter of 1812; and in the Pachalik of Aleppo, in the months of August and September, 1822.

As the mass of the people are seldom able to rise to general views, and are consequently always disposed to ascribe great phenomena to local telluric and atmospheric processes, wherever the shaking of the earth is continued for a long time, fears of the eruption of a new volcano are awakened. In some few cases, this apprehension has certainly proved to be well grounded, as, for instance, in the sudden elevation of volcanic islands, and as we see in the elevation of the volcano of Jorullo, a mountain elevated 1684 feet above the ancient level of the neighboring plain, on the 29th of September 1759, after ninety days of earthquake and subterranean thunder.

If we could obtain information regarding the daily condition of all the earth's surface, we should probably discover that the earth is almost always undergoing shocks at some point of its superficies, and is continually influenced by the reaction p 212 of the interior on the exterior. The frequency and general prevalence of a phenomenon which is probably dependent on the raised temperature of the deepest molten strata explain its independence of the nature of the mineral masses in which it manifests itself. Earthquakes have even been felt in the loose alluvial strata of Holland, as in the neighborhood of Middleburg and vliessingen on the 23d of February, 1828. Granite and mica slate are shaken as well as limestone and sandstone, or as trachyte and amygdaloid. It is not, therefore, the chemical nature of the constituents, but rather the mechanical structure of the rocks, which modifies the propagation of the motion, the wave of commotion. Where this wave proceeds along a coast, or at the foot and in the direction of a mountain chain, interruptions at certain points have sometimes been remarked, which manifested themselves during the course of many centuries. The undulation advances in the depths below, but is never felt at the same points on the surface. The Peruvians* say of these unmoved upper strata that "they form a bridge."

As the mountain chains appear to be raised on fissures, the walls of the cavities may perhaps favor the direction of undulations parallel to them; occasionally, however, the waves of commotion intersect several chains almost perpenducularly. Thus we see them simultaneously breaking through the littoral chain of Venezuela and the Sierra Parime. In Asia, shocks of earthquakes have been propagated from Lahore and from the foot of the Himalaya (22d of January, 1832) transversely across the chain of the Hindoo Chou to Badakschan, the upper Oxus, and even to Bokhara.*

The circles of commotion unfortunately expand occasionally in consequence of a single and usually violent earthquake. It is only since the destruction of Cumana, on the 14th of December, 1797, that shocks on the southern coast have been felt in the mica slate rocks of the peninsula of Maniquarez, situated opposite to the chalk hills of the main land. The advance p 213 from south to north was very striking in the almost uninterrupted undulations of the soil in the alluvial valleys of the Mississippi, the Arkansas, and the Ohio, from 1811 to 1813. It seemed here as if subterranean obstacles were gradually overcome, and that the way being once opened, the undulatory movement could be freely propagated.

Although earthquakes appear at first sight to be simply dynamic phenomena of motion, we yet discover, from well-attested facts, that they are not only able to elevate a whole district above its ancient level (as for instance, the Ulla Bund, Delta of the Indus, or the coast of Chili, in November, 1822), but we also find that various substances have been ejected during the earthquake, as hot water at Catania in 1818; hot steam at New Madrid, in the Valley of the Mississippi, in 1812; irrespirable gases, 'Mofettes', which injured the flocks grazing in the chain of the Andes; mud, black smoke, and even flames, at Messina in 1781, and at Cumana on the 14th of November, 1797. During the great earthquake of Lisbon, on the 1st of November, 1755, flames and columns of smoke were seen to rise from a newly-formed fissure in the rock of Alvidras, near the city. The smoke in this case became more dense as the subterranean noise increased in intensity.*

At the destruction of Riobamba, in the year 1797, when the shocks were not attended by any outbreak of the neighboring volcano, a singular mass called the 'Moya' was uplifted from the earth in numerous continuous conical elevations, the whole being composed of carbon, crystals of augite, and the silicious shields of infusoria. The eruption of carbonic acid gas from fissures in the Valley of the Magdalene, during the earthquake of New Granada, on the 16th of November, 1827, suffocated many snakes, rats, and other animals. Sudden changes of weather, as the occurrence of the rainy season in the tropics, at an unusual period of the year, have sometimes succeeded violent earthquakes in Quito and Peru. Do gaseous fluids rise from the interior of the earth, and mix with the atmosphere? or are these meteorological processes the action of atmospheric electricity disturbed by the earthquake? In the tropical regions of America, where sometimes not a drop of rain falls for ten months together, the natives consider the repeated shocks of earthquakes, which do not endanger the low reed huts, as auspicious harbingers of fruitfulness and abundant rain.

p 214 The intimate connection of the phenomena which we have considered is still hidden in obscurity. Elastic fluids are doublessly the cause of the slight and perfectly harmless trembling of the earth's surface, which has often continued several days (as in 1816, at Scaccia, in Sicily, before the volcanic elevation of the island of Julia), as well as of the terrific explosions accompanied by loud noise. The focus of this destructive agent, the seat of the moving force, lies far below the earth's surface; but we know as little of the extent of this depth as we know of the chemical nature of these vapors that are so highly compressed. At the edges of two craters, Vesuvius, and the towering rock which projects beyond the great abyss of Pichincha, near Quito, I have felt periodic and very regular shocks of earthquakes, on each occasion from 20 to 30 seconds before the burning scoriae or gases were erupted. The intensity of the shocks was increased in proportion to the time intervening between them, and, consequently, to the length of time in which the vapors were accumulating. This simple fact, which has been attested by the evidence of so many travelers, furnishes us with a general solution of the phenomenon, in showing that active volcanoes are to be considered as safety-valves for the immediate neighborhood. The danger of earthquakes increases when the openings of the volcano are closed, and deprived of free communication with the atmosphere; but the destruction of Lisbon, of Caraccas, of Lima, of Cashmir in 1554,* and of so many cities of Calabria, Syria, and Asia Minor, shows us, on the whole, that the force of the shock is not the greatest in the neighborhood of active volcanoes.

As the impeded activity of the volcano acts upon the shocks of the earth's surface, so do the latter react on the volcanic phenomena. Openings of fissures favor the rising of cones of eruption, and the processes which take place in these cones, by forming a free communication with the atmosphere. A column of smoke, which had been observed to rise for months together from the volcano of Pasto, in South America, suddenly disappeared, when on the 4th of February, 1797, the province of Quito, situated at a distance of 192 miles to the south, suffered from the great earthquake of Riobamba. After the earth had continued to tremble for some time through out the whole of Syria, in the Cyclades, and in Euboea, the shocks suddenly ceased on the eruption of a stream of hot mud p 215 on the Lelantine plains near Chalcia.*

The intelligent geographer of Amasea, to whom we are indebted for the notice of this circumstance, further remarks: "Since the craters of Aetna have been opened, which yield a passage to the escape of fire, and since burning masses and water have been ejected, the country near the sea-shore has not been so much shaken as at the time previous to the separation of Sicily from Lower Italy, when all communications with the external surface were closed."

We thus recognize in earthquakes the existence of a volcanic force, which, although every where manifested, and as generally diffused as the internal heat of our planet, attains but rarely, and then only at separate points, sufficient intensity to exhibit the phenomenon of eruptions. The formation of veins, that is to say, the filling up of fissures with crystalline masses bursting forth from the interior (as basalt, melaphyre, and greenstone), gradually disturbs the free intercommunication of elastic vapors. This tension acts in three different ways, either in causing disruptions, or sudden and retroversed elevations, or, finally, as was first observed in a great part of Sweden, in producing changes in the relative level of the sea and land, which, although continuous, are only appreciable at intervals of long period.

Before we leave the important phenomena which we have considered not so much in their individual characteristics as in their general physical and geognostical relations, I would advert to the deep and peculiar impression left on the mind by the first earthquake which we experience, eeven where it is not attended by any subterranean noise.*

This impression is not, p 216 in my opinion, the result of a recollection of those fearful pictures of devastation presented to our imaginations by the historical narratives of the past, but is rather due to the sudden revelation of the delusive nature of the inherent faith by which we had clung to a belief in the immobility of the solid parts of the earth. We are accustomed from early childhood to draw a contrast between the mobility of water and the immobility of the soil on which we tread; and this feeling is confirmed by the evidence of our senses. When, therefore, we suddenly feel the ground move beneath us, a mysterious and natural force, with which we are previously unacquainted, is revealed to us as an active disturbance of stability. A moment destroys the illusion of a whole life; our deceptive faith in the repose of nature vanishes, and we feel transported, as it were, into a realm of unknown destructive forces. Every sound -- the faintest motion in the air -- arrests our attention, and we no longer trust the ground on which we stand. Animals, especially dogs and swine, participate in the same anxious disquietude; and even the crocodiles of the Orinoco, which are at other times as dumb as our little lizards, leave the trembling bed of the river, and run with loud cries into the adjacent forests.

To man the earthquake conveys an idea of some universal and unlimited danger. We may flee from the crater of a volcano in active eruption, or from the dwelling whose destruction is threatened by the approach of the lava stream; but in an earthquake, direct our flight whithersoever we will, we still feel as if we trod upon the very focus of destruction. This condition of the mind is not of long duration, although it takes its origin in the deepest recesses of our nature; and when a series of faint shocks succeed one another, the inhabitants of the country soon lose every trace of fear. On the coasts of Peru, where rain and hail are unknown, no less than the rolling thunder and the flashing lightning, these luminous explosions of the atmosphere are replaced by the subterranean noises which accompany earthquakes.*

Long habit, and the very p 217 prevalent opinion that dangerous shocks are only to be apprehended two or three times in the course of a century, cause faint oscillations of the soil to be regarded in Lima with scarcely more attention than a hail storm in the temperate zone.

Having thus taken a general view of the activity -- the inner life, as it were -- of the Earth, in respect to its internal heat, its electro-magnetic tension, its emanation of light at the poles, and its irregularly-recurring phenomena of motion, we will now proceed to the consideration of the material products, the chemical changes in the earth's surface, and the composition of the atmosphere, which are all dependent on planetary vital activity. We see issue from the ground steam and gaseous carbonic acid, almost always free from the admixture of nitrogen;* carbureted hydrogen gas, which has been used in the Chinese province Sse-tschuan** for several thousand years, and recently in the village of Fredonia, in the State of New York, United States, in cooking and for illumination; sulphureted hydrogen gas and sulphurous vapors; and, more rarely,*** sulphurous and hydrochloric acids.****

Such effusions p 218 from the fissures of the earth not only occur in the districts of still burning or long-extinguished volcanoes, but they may likewise be observed occasionally in districts where neither trachyte nor any other volcanic rocks are exposed on the earth's surface. In the chain of Quindiu I have seen sulphur deposited in mica slate from warm sulphurous vapor at an elevation of 6832 feet* above the level of the sea, while the same species of rock, which was formerly regarded as primitive, contains, in the Cerro Cuello, near Tiscan, south of Quito, an immense deposit of sulphur imbedded in pure quartz.

Exhalations of carbonic acid ('mofettes') are even in our days to be considered as the most important of all gaseous emanations, with respect to their number and the amount of their effusion. We see in Germany, in the deep valleys of the Eifel, in the neighborhood of the Lake of Laach,* in the crater-like valley of the Wehr and in Western Bohemia, exhalations of carbonic acid gas manifest themselves as the last efforts of volcanic activity in or near the foci of an earlier world.

In those earlier periods, when a higher terrestrial temperature existed, and when a great number of fissures still remained unfilled, the processes we have described acted more powerfully, and carbonic acid and hot steam were mixed in larger quantities in the atmosphere, from whence it follows, as Adolph Bronguiart has ingeniously shown,* that the primitive vegetable world must have exhibited almost every where, and independently of geographical position, the most luxurious abundance and the fullest development of organism.

In these constantly warm and damp atmospheric strata, saturated with p 219 carbonic acid, vegetation must have attained a degree of vital activity, and derived the superabundance of nutrition necessary to furnish materials for the formation of the beds of lignite (coal) constituting the inexhaustible means on which are based the physical power and prosperity of nations. Such masses are distributed in basins over certain parts of Europe, occurring in large quantities in the British Islands, in Belgium, in France, in the provinces of the Lower Rhine, and in Upper Silesia. At the same primitive period of universal volcanic activity, those enormous quantities of carbon must also have escaped from the earth which are contained in limestone rocks, and which, if seprated from oxygen and reduced to a solid form, would constitute about the eighth part of the absolute bulk of these mountain masses.*

That portion of the carbon which was not taken up by alkaline earths, but remained mixed with the atmosphere, as carbonic acid, was gradually consumed by the vegetation of the earlier stages of processes of vegetable life, only retained the small quantity which it now possesses, and which is not injurious to the sulphurous vapor have occasioned the destruction of the species of mollusca and fish which inhabited the inland waters of the earlier world, and have given rise to the formation of the contorted beds of gypsum, which have doubtless been frequently affected by shocks of earthquakes.

Gaseous and liquid fluids, mud, and molten earths, ejected from the craters of volcanoes, which are themselves only a kind of "intermittent springs," rise from the earth under precisely analogous physical relations.*

All these substances owe their temperature and their chemical character to the place of their origin. The 'mean' temperature of aqueous springs is less than that of the air at the point whence they emerge, if the water flow from a height; but their heat increases with the depth of the strata with which they are in contact at their origin. We have already spoken of the numerical law regulating this increase. The blending of waters that have come from the height of a mountain with those that have sprung from the depths of the earth, render it difficult to determine the position of the 'isogeothermal lines'* (lines of equal internal p 220 terrestrial temperature, when this determination is to be made from the temperature of flowing springs.

Such at any rate, is the result I have arrived at from my own observations and those of my fellow-travelers in Northern Asia. The temperature of springs, which has become the subject of such continuous physical investigation during the last half century, depends, like the elevation of the line of perpetual snow, on very many simultaneous and deeply-involved causes. It is a function of the temperature of the stratum in which they take their rise, of the specific heat of the soil, and of the quantity and temperature of the meteoric water,* which is itself different from the temperature of the lower strata of the atmosphere, according to the different modes of its origin in rain, snow, or hail.**

Cold springs can only indicate the mean atmospheric temperature p 221 when they are unmixed with the waters rising from great depths, or descending from considerable mountain elevations, and when they have passed through a long course at a depth from the surface of the earth which is equal in our latitudes to 40 or 60 feet, and according to Boussingault, to about one foot in the equinoctial regions,* these being the depths at which the invariability of the temperature begins in the temperate and torrid zones, that is to say, the depths at which horary, diurnal, and monthly changes of heat in the atmosphere cease to be perceived.

_______________________________________________________ Stations Temperature at Mean Height, in within 1 French foot Temperature English Tropic [1.006 of the of the feet, above Zones. English foot] air. the level below the of the sea. earth's surface. _______________________________________________________

Guayaquil 78.8 78.1 0 Anserma Nuevo 74.6 74.8 3444 Zupia 70.7 70.7 4018 Popayan 64.7 65.6 5929 Quito 59.9 59.9 9559 ________________________________________________________

The doubts about the temperature of the earth within the tropics, of which I am probably, in some degree, the cause, by my observations on the Cave of Caripe (Cueva del Guacharo), 'Rel. Hist.', t. iii., p. 191-196), are resolved by the consideration that I compared the presumed mean temperature of the air of the convent of Caripe, 65.3 degrees, not with the temperature of the air of the cave, 65.6 degrees, but with the temperature of the subterranean stream, 62.3degrees, although I observed ('Rel. Hist.', t. iii., p. 146 and 195) that mountain water from a great height might probably be mixed with the water of the cave.

Hot springs issue from the most various kinds of rocks. The hottest permanent springs that have hitherto been observed are, as my own researches confirm, at a distance from all volcanoes. I will here advert to a notice in my journal of the Aguas Calientes de las Trincheras', in South America, between Porto Cabello and Nueva Valencia, and the 'Aguas de Comangillas', in the Mexican territory, near Guanaxuato; the former of these, which issued from granite, had a temperature of 194.5 degrees; the latter, issuing from basalt, 205.5degrees. The depth of the source from whence the water flowed with this temperature, judging from what we know of the law of the increase of heat in the interior of the earth, was probably 7140 feet, or above two miles. If the universally-diffused terrestrial heat be the cause of thermal springs, as of active volcanoes, the rocks can only exert an influence by the different capacities p 222 for heat and by their conducting powers. The hottest of all permanent springs (between 203 degrees and 209 degrees) are likewise, in a most remarkable degree, the purest, and such as hold in solution the smallest quantity of mineral substances. Their temperature appears, on the whole, to be less constant than that of springs between 122 degrees and 165 degrees, which in Europe, at least, have maintained, in a most remarkable manner, their 'invariability of heat and mineral contents' during the last fifty or sixty years, a period in which thermometrical measurements and chemical analyses have been applied with increasing exactness. Boussingault found in 1823 that the thermal springs of Las Tricheras had risen 12 degrees during the twenty-three years that had intervened since my travels in 1800.*

This calmly-flowing spring is therefore now nearly 12 degrees hotter than the intermittent fountains of the Geyser and the Strokr, whose temperature has recently been most carefully determined by Krug of Nidda. A very striking proof of the origin of hot springs by the sinking of cold meteoric water into the earth, and by its contact with a volcanic focus, is afforded by the volcano of Jorulla in Mexico, which was unknown before my American journey. When, in September, 1759, Jorullo was suddenly elevated into a mountain 1183 feet above the level of the surrounding plain, two small rivers, the 'Rio de Cuitimba' and 'Rio de San Pedro', disappeared, and some time afterward burst forth again, during violent shocks of an earthquake, as hot springs, whose temperature I found in 1803 to be 186.4 degrees.

The springs in Greece still evidently flow at the same places as in the times of Hellenic antiquity. The spring of Erasinos, two hours' journey to the south of Argos, on the declivity of Chaon, is mentioned by Herodotus. At Delphi we still see Cassotis (now the springs of St. Nicholas) rising south of the Lesche, and flowing beneath the Temple of Apollo; Castalia, at the foot of Phaedriadae; Pirene, near Acro-Corinth; and the hot baths of Aedipsus, in Euboea, in which Sulla bathed during the Mithridatic war.*

I advert with pleasure to these p 223 facts, as they show us that, even in a country subject to frequent and violent shocks of earthquakes, the interior of our planet has retained for upward of 2000 years its ancient configuration in reference to the course of the open fissures that yield a passage to these waters. The 'Fontaine jaillissante' of Lillers, in the Department des Pas de Calais, which was bored as early as the year 1126, still rises to the same height and yields the same quantity of water; and, as another instance, I may mention that the admirable geographer of the Caramanian coast, Captain Beaufort, saw in the district of Phaselis the same flame fed by emissions of inflammable gas which was described by Pliny as the flame of the Lycian Chimera.*

The observation made by Arago in 1821, that the deepest Artesian wells are the warmest,* threw great light on the origin of thermal springs, and on the establishment of the law that terrestrial heat increases with increasing depth.

It is a remarkable fact, which has but recently been noticed, that at the close of the third century, St. Patricus,* probably Bishop of Pertusa, was led to adopt very correct views regarding the phenomenon of the hot springs at Carthage.

On being asked what was the cause of boiling water bursting from the earth, he replied, "Fire is nourished in the clouds and in the interior p 224 of the earth, as Aetna and other mountains near Naples may teach you. The subterranean waters rise as if through siphons. The cause of hot springs is this: waters which are more remote from the subterranean fire are colder, while those which rise nearer the fire are heated by it, and bring with them to the surface which we inhabit an insupportable degree of heat."

As earthquakes are often accompanied by eruptions of water and vapors, we recognize in the 'Salses',* of small mud volcanoes, a transition from the changing phenomena presented by these eruptions of vapor and thermal springs to the more powerful and awful activity of the streams of lava that flow from volcanic mountains.

If we consider these mountains as springs of molten earths producing volcanic rocks, we must remember that thermal water, when impregnated with carbonic acid and sulphurous gases, are continually forming horizontally ranged strata of limestone (travertine) or conical elevations, as in Northern Africa (in Alberia), and in the Banos of Caxamarca, on the western declivity of the Peruvian Cordilleras. The travertine of Van Diemen's Land (near Hobart Town) contains, according to Charles Darwin, remains of a vegetation that no longer exists. Lava and travertine, which are constantly forming before our eyes, present us with the two extremes of geognostic relations.

'Salses' deserve more attention than they have hitherto received from geognosists. Their grandeur has been overlooked because of the two conditions to which they are subject; it is only the more peaceful state, in which they may continue for centuries, which has generally been described: their origin is, however, accompanied by earthquakes, subterranean thunder, the elevation of a whole district, and lofty emissions of flame of short duration. When the mud volcano of Jokmali began to form on the 27th of November, 1827, in the peninsula of Abscheron, on the Caspian Sea, east of Baku, the flames flashed up to an extraordinary height for three hours, while during the next twenty hours they scarcely rose three feet above the crater, from which mud was ejected. Near the village of Baklichli, west of Baku, the flames rose so high that p 225 they could be seen at a distance of twenty-four miles. Enormous masses of rock were torn up and scattered around. Similar masses may be seen round the now inactive mud volcano of Monte Ziblo, near Sassuolo, in Northern Italy. The secondary condition of repose has been maintained for upward of fifteen centuries in the mud volcanoes of Girgenti, the 'Macalubi', in Sicily, which have been described by the ancients. These salses consist of many contitiguous conical hills, from eight to ten, or even thirty feet in height, subject to variations of elevation as well as of form. Streams of argillaceous mud, attended by a periodic development of gas, flow from the small basins at the summits, which are filled with water; the mud, although usualy cold is sometimes at a high temperature, as at Damak, in the province of Samarang, in the island of Java. The gases that are developed with loud noise differ in their nature consisting for instance, of hydrogen mixed with naphtha, or of carbonic acid, or, as Parrot and myself have shown (in the peninsula of Taman, and in the 'Volcancitos de Turbaco', in South America), of almost pure nitrogen.*

Mud volcanoes, after the first violent explosion of fire, which is not, perhaps, in an equal degree common to all, present to the spectator an image of the uninterrupted but weak activity of the interior of our planet. The communication with the deep strata in which a high temperature prevails is soon closed, and the coldness of the mud emissions of the salses seems to indicate that the seat of the phenomenon can not be far removed from the surface during their ordinary condition. The reaction of the interior of the earth on its external surface is exhibited with totally different force in true volcanoes or igneous mountains, at points of the earth in which a permanent, or, at least, continually-renewed connection with the volcanic force is manifested. We must here carefully distinguish between the more or less intensely developed volcanic phenomena, as for instance, between earthquakes, thermal, aqueous, and gaseous springs, mud volcanoes, and the appearance of bell-formed or dome-shaped trachytic rocks without openings; the opening of these rocks, or of the elevated beds of basalt, as p 226 craters of elevation; and, lastly, the elevation of a permanent volcano in the crater of elevation, or among the 'debris' of its earlier formation. At different periods, and in different degrees of activity and force, the permanent volcanoes emit steam acids, luminous scoriae, or, when the resistance can be overcome, narrow, band-like streams of molten earths. Elastic vapors sometimes elevate either separate portions of the earth's crust into dome-shaped unopened masses of feldspathic trachyte and dolerite (as in Puy de Dome and Chimborazo), in consequence of some great or local manifestation of force in the interior of our planet, or the upheaved strata are broken through and curved in such a manner as to form a steep rocky ledge on the opposite inner side, which then constitutes the inclosure of a crater of elevation. If this rocky ledge has been uplifted from the bottom of the sea, which is by no means always the case, it determines the whole physiognomy and form of the island. In this manner has arisen the circular form of Palma, which has been described with such admirable accuracy by Leopold von Buch, and that of Nisyros,* in the Aegean sea.

Sometimes half of the annular ledge has been destroyed, and in the bay formed by the encroachment of the sea corallines have built their cellular habitations. Even on continents craters of elevation are often filled with water, and embellish in a peculiar manner the character of the landscape. Their origin is not connected with any determined species of rock: they break out in basalt, trachyte, leucitic porphyry (somma), or in doleritic mixtures of augite and labradorite; and hence arise the different nature and external conformation of these inclosures of craters. No phenomena of eruption are manifested in such craters, as they open no permanent channel of communication with the interior, and it is but seldom that we meet with traces of volcanic activity either in the neighborhood or in the interior of these craters. The force which was able to produce so important an action must have been long accumulating in the interior before it could overpower the resistance of the mass pressing upon it; it sometimes, for instance, on the origin of new islands, will raise granular rocks and conglomerated masses (strata of tufa filled with marine plants) above the surface of the sea. The compressed vapors escape through the crater of elevation, but a large mass soon falls back and closes the opening, which had been only formed by these manifestations of force. No volcano can, therefore, p be produced.*

A volcano, properly so called, exists only where a permanent connection is established between the interior of the earth and the atmosphere, and the reaction of the interior on the surface then continues during long periods of time. It may be interrupted for centuries, as in the case of Vesuvius Fisove,* and then manifest itself with renewed activity.

In the time of Nero, men were disposed to rank Aetna among the volcanic mountains which were graduallybecoming extinct,* and subsequently Aelian** even maintained that mariners could no longer see the sinking summit of the mountain from so great a distance at sea.

Where these evidences -- these old scaffoldings of eruption, I might almost say -- still exist, the volcano rises from a crater of elevation, while a high rocky wall surrounds, like an amphitheater, the isolated conical mount, and forms around it a kind of easing of highly elevated p 228 strata. Occasionally not a trace of this inclosure is visible, and the volcano, which is not always conical rises immediately from the neighboring plateau in an elongated form, as in the case of Pichincha,* at the foot of which lies the city of Quito.

As the nature of rocks, or the mixture (grouping) of simple minerals into granite, gneiss, and mica slate, or into trachyte, basalt, and dolorite, is independent of existing climates, and is the same under the most varied latitudes of the earth, so also we find every where in inorganic nature that the same laws of configuration regulate the reciprocal superposition of the strata of the earth's crust, cause them to penetrate one another in the form of veins, and elevate them by the agency of elastic forces. This constant recurrence of the same phenomena is most strikingly manifested in volcanoes. When the mariner, amid the islands of some distant archipelago, is no longer guided by the light of the same stars with which he had been familiar in his native latitude, and sees himself surrounded by palms and other forms of an exotic vegetation, he still can trace, reflected in the individual characteristics of the landscape, the forms of Vesuvius, of the come-shaped summits of Auvergne, the craters of elevation in the Canaries and Azores, or the fissures of eruption in Iceland. A glance at the satellite of our planet will impart a wider generalization to this analogy of configuration. by means of the charts that have been drawn in accordance with the observations made with large telescopes, we may recognize in the moon, where water and air are both absent, vast craters of elevation surrounding or supporting conical mountains, thus affording incontrovertible evidence of the effects produced by the reaction of the interior on the surface, favored by the influence of a feebler force of gravitation.

Although vocanoes are justy termed in many languages "fire-emitting mountains," mountains of this kind are not formed by the gradual accumulation of ejected currents of lava, but their origin seems rather to be a general consequence of the sudden elevation of soft masses of trachyte or labradoritic augite. The amount of the elevating force is manifested p 229 by the elevation of the volcano, which varies from the inconsiderable height of a hill (as the volcano of Cosima, one of the Japanese Kurile islands) to that of a cone above 19,000 feet in height. It has appeared to me that relations of height have a great influence on the occurrence of eruptions, which are more frequent in low than in elevated volcanoes. I might instance the series presented by the following mountains: Stromboli, 2318 feet; Guacamayo, in the province of Quixos, from which detonations are heard almost daily (I myself often heard them at Chillo, near Quito, a distance of eighty-eight miles); Vesuvius, 3876 feet; Aetna, 10871 feet; the Peak of Teneriffe, 12,175 feet; and Cotopaxi, 19,069 feet. If the focus of these volcanoes be at an equal depth below the surface, a greater force must be required where the fused masses have to be raised to an elevation six or eight times greater than that of the lower eminences. While the volcano Stromboli (Strongyle) has been incessantly active since the Homeric ages, and has served as a beacon-light to guide the mariner in the Tyrrhenian Sea, loftier volcanoes have been characterized by loong intervals of quiet. Thus we see that a whole century often intervenes between the eruptions of most of the colossi which crown the summits of the Cordilleras of the Andes. Where we meet with exceptions to this law, to which I long since drew attention, they must depend upon the circumstance that the connections between the volcanic foci and the crater of eruption can not be considered as equaly permanent in the case of all volcanoes. The channel of communication may be closed for a time in the case of the lower ones, so that they less frequently come to a state of eruption, although they do not, on that account, approach more nearly to their final extinction.

These relations between the absolute height and the frequency of volcanic eruptions, as far as they are externally perceptible, are intimately connected with the consideration of the local conditions under which lava currents are erupted. Eruptions from the crater are very unusual in many mountains, generally occurring from lateral fissures (as was observed in the case of Aetna, in the sixteenth century, by the celebrated historian Bembo, when a youth*), whenever the sides p 230 of the upheaved mountain were least able, from their configuration and position, to offer any resistance.

Cones of eruption are sometimes uplifted on these fissures; the larger ones, which are erroneously termed 'new volcanoes', are ranged together in line marking the direction of a fissure, which is soon reclosed, while the smaller ones are grouped together covering a whole district with their dome-like or hive-shaped forms. To the latter belong the 'hornitos de Jorullo',I the cone of Vesuvius erupted in October, 1822, that of Awatscha, according to Postels, and those of the lava-field mentioned by Erman, near the Baidar Mountains, in the peninsula of Kamtschatka.

When volcanoes are not isolated in a plain, but surrounded, as in the double chain of the Andes of Quito, by a table-land having an elevation from nine to thirteen thousand feet, this circumstance may probably explain the cause why no lava streams are formed* during the most dreadful eruption of ignited scoriae accompanied by detonations heard at a distance of more than a hundred miles.

Such are the volcanoes of Popayan, those of the elevated plateau of Los Pastos and of the Andes of Quito, with the exception, perhaps, in the case of the latter, of the volcano of Antisana. The height of the cone of cinders, and the size and form of the crater, are elements of configuration which yield an especial and individual character to volcanoes, although the cone of cinders and the crater are both wholly independent of the dimensions of the mountain. Vesuvius is more than three times lower than the Peak of Teneriffe; its cone of cinders rises to one third of the height of the whole mountain, while the cone of cinders of the Peak is only 1/22d of its altitude.

In a much higher volcano than that of Teneriffe, the Rueu Pichincha, other relations occur p 231 which approach more nearly to that of Vesuvius. Among all the volcanoes that I have seen in the two hemispheres, the conical form of Cotopaxi is the most beautifully regular. A sudden fusion of the snow at its cone of cinders announces the proximity of the eruption. Before the smoke is visible in the rarefied strata of air surrounding the summit and the opening of the crater, the walls of the cone of cinders are sometimes in a state of glowing heat, when the whole mountain presents an appearance of the most fearful and portentous blackness. The crater, which, with very few exceptions, occupies the summit of the volcano, forms a deep, caldron-like valley, which is often accessible, and whose bottom is subject to constant alterations. The great or lesser depth of the crater is in many volcanoes likewise a sign of the near or distant occurrence of an eruption. Long, narrow fissures, from which vapors issue forth, or small rounding hollows filled with molten masses, alternately open and close in the caldron-like valley; the bottom rises and sinks, eminences of scoriae and cones of eruption are formed, rising sometimes far over the walls of the crater, and continuing for years together to impart to the volcano a peculiar character, and then suddenly fall together and disappear during a new eruption. The openings of these cones of eruption, which rise from the bottom of the crater, must not, as is too often done, be confounded with the crater which incloses them. If this be inaccessible from extreme depth and from the perpendicular descent, as in the case of the volcano of Rucu Pichincha, which is 15,920 feet in height, the traveler may look from the edge on the summit of the mountains which rise in the sulphurous atmosphere of the valley at his feet; and I have never beheld a grander or more remarkable picture than that presented by this volcano. In the interval between two eruptions, a crater may either present no luminous appearance, showing merely open fissures and ascending vapors, or the scarcely heated soil may be covered by eminences of scoriae, that admit of being approached without danger, and thus present to the geologist the spectacle of the eruption of burning and fused masses, which fall back on the ledge of the cone of scoriae, and whose appearance is regularly announced by small wholly local earthquakes. Lava sometimes streams forth from the open fissures and small hollows, without breaking through or escaping beyond the sides of the crater. If, however, it does break through, the newly-opened terrestrial stream generally flows in such a quiet and well-defined course, that the deep valley, which we term the crater, remains accessible p 232 even during periods of eruption. It is impossible, without an exact representation of the configuration -- the normal type, as it were, of fire-emitting mountains, to form a just idea of those phenomena which, owing to fantastic descriptions and an undefined phraseology, have long been comprised under the head of 'craters, cones of eruption', and 'volcanoes'. The marginal ledges of craters vary much less than one would be led to suppose. A comparison of Saussure's measurements with my own yields the remarkable result, for instance, that in the course of forty-nine years (from 1773 to 1822), the elevation of the northwestern margin of Mount Vesuvius ('Rocca del Palo') may be considered to have remained unchanged.*

Volcanoes which, like the chain of the Andes, lift their summits high above the boundaries of the region of perpetual snow, present peculiar phenomena. The masses of snow, by their sudden fusion during eruptions, occasion not only the most fearful inundations and torrents of water, in which smoking scoriae are borne along on thick masses of ice, but they likewise exercise a constant action, while the volcano is in a state of perfect repose, by infiltration into the fissures of the trachytic rock. Cavities which are either on the declivity or at the foot of the mountain are gradually converted into subterranean resevoirs of water, which communicate by numerous narrow openings with mountain streams, as we see exemplified in the highlands of Quito. the fishes of these rivulets multiply, especially in the obscurity of the hollows; and when the shocks of earthquakes, which precede all eruptions in the andes, have violently shaken the whole mass of the volcano, these subterranean caverns are suddenly opened, and water, fishes, and tufaceous mud are all ejected together. It is through this singular phenomenon* that the inhabitants of the highlands of Quito became acquainted with the existence of the little cyclopic fishes, termed by them the prenadilla.

On the night between the 19th and 20th of June, 1698, when the summit of Carguairazo, a mountain 19,720 feet in height, fell in, leaving only two huge masses of rock remaining of the ledge of the crater, a space of nearly thirty-two square miles was overflowed and devastated by streams of liquid tufa and argillaceous mud ('lodazales'), containing large quantities of dead fish. p 233 In like manner, the putrid fever, which raged seven years previously in the mountain town of Ibarra, north of Quito, was ascribed to the ejection of fish from the volcano of Imbaburu.*

Water and mud, which flow not from the crater itself, but from the hollows in the trachytic mass of the mountain, can not, strictly speaking, be classed among volcanic phenomena. They are only indirectly connected with the volcanic activity of the mountain, resembling, in that respect, the singular meteorological process which I have designated in my earlier writings by the term of 'volcanic storm'. The hot stream which rises from the crater during the eruption and spreads itself in the atmosphere, condenses into a cloud, and surrounds the column of fire and cinders which rises to an altitude of many thousand feet. The sudden condensation of the vapors, and, as Gay-Lussac has shown, the formation of a cloud of enormous extent, increase the electric tension. Forked lightning flashes from the column of cinders, and it is then easy to distinguish (as at the close of the eruption of Mount Vesuvius, in the latter end of October, 1822) the rolling thunder of the volcanic storm from the detonations in the interior of the mountain. the flashes of lightning that darted from the volcanic cloud of steam, as we learn from Olafsen's report, killed eleven horses and two men, on the eruption of the volcano of Katlagia, in Iceland, on the 17th of October, 1755.

Having thus delineated the structure and dynamic activity of volcanoes, it now remains for us to throw a glance at the differences existing in their material products. The subterranean forces sever old combinations of matter in order to produce new ones, and they also continue to act upon matter as long as it is in a state of liquefaction from heat, and capable of being displaced. The greater or less pressure under which merely softened or wholly liquid fluids are solidified, appears to constitute the main difference in the formation of Plutonic and volcanic rocks. The mineral mass which flows in narrow, elongated streams from a volcanic opening (an earth-spring), is called lava. where many such currents meet and are arrested in their course, they expand in width, filling large basins, in which they become solidified in superimposed strata. These few sentences describe the general character of the products of volcanic activity.

p 234 Rocks which are merely broken through by the volcanic action are often inclosed in the igneous products. Thus i have found angular fragments of feldspathic syenite imbedded in the black augitic lava of the volcano of Jorullo, in Mexico; but the masses of dolomite and granular limestone, which contain magnificent clusters of crystalling fossils (vesuvian and garnets, covered with mejonite, nepheline, and sodalite), are not the ejected products of Vesuvius, these belonging rather to very generally distributed formations, viz., strata of tufa, which are more ancient than the elevation of the Somma and of Vesuvius, and are probably the products of a deep-seated and concealed submarine volcanic action.*

We find five metals among the products of existing volcanoes, iron, copper, lead, arsenic, and selenium, discovered by Stromeyer in the crater of Volcano.*

The vapors that rise from the 'fumarolles' cause the sublimation of the chlorids of iron, copper, lead, and ammonium; iron glanceI and chlorid of sodium (the latter often in large quantities) fill the cavities of recent lava streams and the fissures of the margin of the crater.

The mineral composition of lava differs according to the nature of the crystalline rock of which the volcano is formed, the height of the point where the eruption occurs, whether at the foot of the mountain or in the neighborhood of the crater, and the condition of temperature of the interior. Vitreous volcanic formations, obsidian, pearl-stone, and pumice, are entirely wanting in some volcanoes, while in the case of others they only proceed from the crater, or, at any rate, from very considerable heights. These important and involved relations can only be explained by very accurate crystallographic and chemical investigations. My fellow-traveler in Siberia, Gustav Rose, and subsequently Hermann Abich, have already been able, by their fortunate and ingenious researches, to throw much light on the structural relations of the various kinds of volcanic rocks.

p 235 The greater part of the ascending vapor is mere steam. When condensed, this forms springs, as in Pantellaria,Iwhere they are used by the goatherds of the island.

On the morning of the 26th of October, 1822, a current was seen to flow from a lateral fissure of the crater of Vesuvius, and was loong supposed to have been boiling water; it was, however, shown, by Monticelli's accurate investigations, to consist of dry ashes, which fell like sand, and of lava pulverized by friction. The ashes, which sometimes darken the air for hours and days together, and produce great injury to the vineyards and olive groves by adhering to the leaves, indicate by their columnar ascent, impelled by vapors, the termination of every great eqrthquake. This is the magnificent phenomenon which Pliny the younger, in his celebrated letter to Cornelius Tacitus, compares, in the case of Vesuvius, to the form of a lofty and thickly-branched and foliaceous pine. That which is described as flames in the eruption of scoriae, and the radiance of the glowing red clouds that hover over the crater, can not be ascribed to the effect of hydrogen gas in a state of combustion. They are rather reflections of light which issue from molten masses, projected high in the air, and also reflections from the burning depths, whence the glowing vapors ascend. We will not, however, attempt to decide the nature of the flames, which are occasionally seen now, as in the time of Strabo, to rise from the deep sea during the activity of littoral volcanoes, or shortly before the elevation of a volcanic island.

When the questions are asked, what is it that burns in the volcano? what excites the heat, fuses together earths and metals, and imparts to lava currents of thick layers a degree of heat that lasts for many years? it is necessarily implied that volcanoes must be connected with the existence of substances capable of maintaining combustion, like the beds of coal in subterranean fires.

According to the different phases of chemical science, bitumen, pyrites, the moist admixture of finely-pulverized sulphur and iron, pyrophoric substances, and the metals of the alkalies and earths, have in turn been designated as the cause of intensely active volcanic phenomena. The great chemist, Sir Humphrey Davy, to whom we are indebted for the knowledge of the most combustible metallic p 236 substances, has himself renounced his bold chemical hypothesis in his last work ('Consolation in Travel, and last Days of a Philosopher') -- a work which can not fail to excite in the reader a feeling of the deepest melancholy. the great mean density of the earth (5.44), when compared with the specific weight of potassium (0.865), of sodium (-.972), or of the metals of the earths (1.2), and the absence of hydrogen gas in the gaseous emanations from the fissures of craters, and from still warm streams of lava, besides many chemical considerations, stand in opposition with the earlier conjectures of Davy and Ampere.*

If hydrogen were evolved from erupted lava, how great must be the quantity of the gas disengaged, when, the seat of the volcanic activity being very low, as in the case of the remarkable eruption at the foot of the Skaptar Jokul in Iceland (from the 11th of June to the 3d of August, 1783, described by Mackenzie and Soemund Magnussen), a space of many square miles was covered by streams of lava, accumulated to the thickness of several hundred feet! Similar difficulties are opposed to the assumption of the penetration of the atmospheric air into the crater, or, as it is figuratively expressed, the 'inhalation of the earth', when we have regard to the small quantity of nitrogen emitted. So general, deep-seated, and far-propagated an activity as that of volcanoes, can not assuredly have its source in chemical affinity, or in the mere contact of individual or merely locally distributed substances. Modern geognosy* rather seeks the cause of this activity in the increased temperature with the increase of depth at all degrees of latitude, in that powerful internal heat which our planet owes to its first solidification, its formation in the regions of space, and to the spherical contraction of p 237 matter revolving elliptically in a gaseous condition.

We have thus mere conjecture and supposition side by side with certain knowledge. A philosophical study of nature strives ever to elevate itself above the narrow requirements of mere natural description, and does not consist, as we have already remarked, in the mere accumulation of isolated facts. The inquiring and active spirit of man must be suffered to pass from the present to the past, to conjecture all that can not yet be known with certainty, and still to dwell with pleasure on the ancient myths of geognosy which are presented to us under so many various forms. If we consider volcanoes as irregular intermittent springs, emitting a fluid mixture of oxydized metals, alkalies, and earths, flowing gently and calmy wherever then find a passage, or being upheaved by the powerful expansive force of vapors, we are involuntarily led to remember the geognostic visions of Plato, according to which hot springs, as well as all volcanic igneous streams, were eruptions that might be traced back to one generally distributed subterranean cause, 'Pyriphlegethon'.*

p 238 The different volcanoes over the earth's surface, when they are considered independently of all climatic differences, are acutely and characteristically classified as central and linear volcanoes. Under the first name are comprised those which constitute the central point of many active mouths of eruption, distributed almost regularly in all directions; under the second, those lying at some little distance from one another, forming, as it were, chimneys or vents along an extended fissure. Linear volcanoes again admit of further subdivision, namely, those which rise like separate conical islands from the bottom of the sea, being generally parallel with a chain of primitive mountains, whose foot they appear to indicate, and those volcanic chains which are elevated on the highest ridges of these mountain chains, of which they form the summits.*

The Peak of Teneriffe, for instance, is a central volcano, being the central point of the volcanic group to which the eruption of Palma and Landerote may be referred. The long, rampart-like chain of the Andes, which is sometimes single, and sometimes divided into two or three parallel branches, connected by various transverse ridges, presents, from the south of Chili to the northwest coast of America, one of the grandest instances of a continental volcanic chain. The proxiimity of p 239 active volcanoes is always manifested in the chain of the Andes by the appearance of certain rocks (as dolerite, melaphyre, trachyte, andesite, and dioritic porphyry), which divide the so-called primitive rocks, the transition slates and sandstones, and the stratified formations. the constant recurrence of this phenomenon convinced me long since that these sporadic rocks were the seat of volcanic phenomena, and were connected with volcanic eruptions. At the foot of the grand Tunguragua, near Penipe, on the banks of the Rio Puela, I first distinctly observed mica slate resting on granite, broken through by a volcanic rock.

In the volcanic chain of the New Continent, the separate volcanoes are occasionally, when near together in mutual dependence upon one another; and it is even seen that the volcanic activity for centuries together has moved on in one and the same direction, as for instance, from north to south in the province of Quito.*

The focus of the volcanic action lies below the whole of the highlands of this province; the only channels of communication with the atmosphere are, however, those mountains which we designate by special names, as the mountains of Pichincha, Cotopaxi, and Tunguragua, and which, from their grouping, elevation, and form, constitute the grandest and most picturesque spectacle to be found in any volcanic district of an equally limited extent. Experience shows us, in many instances, that the extremities of such groups of volcanic chains are connected together by subterranean communications; and this fact reminds us of the ancient and true expression made use of by Seneca,* that the igneous mountain is only the issue of the more deeply-seated volcanic forces.

In the Mexican highlands a mutual dependence is p 240 also observed to exist among the volcanic mountains Orizaba, Popocatepel, Jorullo, and Colima; and I have shown* that they all lie in one direction between 18 degrees 59' and 19 degrees 12' north latitude, and are situated in a transverse fissure running from sea to sea.

The volcano of Jorullo broke forth on the 29th of September, 1759, exactly in this direction, and over the same transverse fissure, being elevated to a height of 1604 feet above the level of the surrounding plain. The mountain only once emitted an eruption of lava, in the same manner as is recorded of Mount Epomeo in Ischia, in the year 1302. But although Jorullo, which is eighty miles from any active volcano, is in the strict sense of the word a new mountain, it must not be compared with Monte Nuovo, near Puzzuolo, which first appeared on the 19th of September, 1538, and is rather to be classed among craters of elevation. I believe that I have furnished a more natural explanation of the eruption of the Mexican volcano, in comparing its appearance to the elevation of the Hill of Methone, now Methana, in the peninsula of Troezene. The description given by Strabo and Pausanias of this elevation, led one of the Roman poets, most celebrated for his richness of fancy, to develop views which agree in a remarkable manner with the theory of modern geognosy. "Near Troezene is a tumulus, steep and devoid of trees, once a plain, now a mountain. The vapors inclosed in dark caverns in vain seek a passage by which they may escape. The heavier earth, inflated by the force of the compressed vapors, expands like a bladder filled with air, or like a goat-skin. The ground has remained thus inflated, and the high projecting eminence has been solidified by time into a naked rock." Thus picturesquely, and, as analogous phenomena justify us in believing, thus truly has Ovid described that great natural phenomenon which occurred 282 years before our era, and consequently, 45 years bfore the volcanic separation of Thera (Santorino) and Therasia, between Troezene and Epidaurus, on the same spot where Russegger has found veins of trachyte.*

p 241 Santorino is the most important of all the 'islands of eruption' belonging to volcanic chains.*

It combines within itself p 242 the history of all islands of elevation. For upward of 2000 years, as far as history and tradition certify, it would appear as if nature were striving to form a volcano in the midst of the crater of elevation."*

Similar insular elevations, and almost always at regular intervals of 80 or 90 years,* have been manifested in the island of St. Michael, in the Azores; but in this case the bottom of the sea has not been elevated at exactly the same parts.**

The island which Captain Tillard named 'Sabrina', appeared unfortunately at a time (the 30th of January, 1811) when the political relations of the maritime nations of Western Europe prevented that attention being bestowed upon the subject by scientific institutions which was afterward directed to the sudden appearance (the 2d of July, 1831), and the speedy destruction of the igneous island of Ferdinandea in the Sicilian Sea, between the limestone shores of Sciacca and the purely volcanic island of Pantellaria.*

p 243 The geographical distribution of the volcanoes which have been in a state of activity during historical times, the great number of insular and littoral volcanic mountains, and the occasional, although ephemeral, eruptions in the bottom of the sea, early led to the belief that volcanic activity was connected with the neighborhood of the sea, and was dependent upon it for its continuance. "For many hundred years," says Justinian, or rather Trogus Pompeius, whom he follows,* "Aetna and the Aeolian Islands have been burning, and how could this have continued so long if the fire had not been fed by the p 244 neighboring sea?"**

In order to explain the necessity of the vicinity of the sea, recourse has been had, even in modern times, to the hypothesis of the penetration of sea water into the foci of volcanic agency, that is to say, into deep-seated terrestrial strata. When I collect together all the facts that may be derived from my own observation and the laborious researches of others, it appears to me that every thing in this great quantity of aqueous vapors, which are unquestionably exhaled from volcanoes even when in a state of rest, be derived from sea water impregnated with salt, or rather, perhaps with fresh meteoric water; or whether the expansive force of the vapors (which, at a depth of nearly 94,000 feet, is equal to 2800 atmospheres) would be able at different depths to counterbalance the hydrostatic pressure of the sea, and thus afford them, under certain conditions, a free access to the focus;* or whether the formation of metallic chlorids, the presence of chlorid of sodium in the fissures of the crater, and the frequent mixture of hydrochloric acid with the aqueous vapors, necessarily imply access of sea water; or, finally, whether the repose of volcanoes (either when temporary, or permanent and complete) depends upon the closure of the channels by which the sea or meteoric water was conveyed, or whether the absence of flames and of exhalations of hydrogen (and sulphureted hydrogen gas seems more characteristic of solfataras than of active volcanoes) is not directly at variance p 245 with the hypothesis of the decomposition of great masses of water?**

The discussion of these important physical questions does not come within the scope of a work of this nature; but, while we are considering these phenomena, we would enter somewhat more into the question of the geographical distribution of still active volcanoes. We find, for instance, that in the New World, three, viz., Jorullo, Popocatepetl, and the volcano of De la Fragua, are situated at the respective distances of 80, 132, and 196 miles from the sea-coast, while in Central Asia, as Abel Remusat* first made known to geognosists, the Thianschan (Celestial Mountains), in which are situated the lava-emitting mountain of Pe-schan, the solfatara of Urumtsi, and the still active igneous mountain (Ho-tscheu) of Turfan, lie at an almost equal distance (1480 to 1528 miles) from the shores of the Polar Sea and those of the Indian Ocean.

Pe-schan is also fully 1360 miles distant from the Caspian Sea,* and 172 and 218 miles from the seas of Issikul and Balkasch.

It is a fact worthy of notice, that among the four great parallel mountain chains which traverse the Asiatic continent from east to west, the Altai, the Thianschan, the Kuen-lun, and the Himalaya, it is not the latter chain, which is nearest to Kuen-lun, at the distance of 1600 and 720 miles from the sea, which have fire-emitting mountains like Aetna and Vesuvius, and generate ammonia like the volcano of Guatimala. Chinese writers undoubtedly speak of lava streams when they describe the emissions of smoke and flame, which, issuing from Pe-schan, devastated a space measuring ten li* in the first and seventh centuries of our era.

Burning masses of stone flowed, according to their description "like thin melted fat." The facts that have been enumerated, and to which sufficient attention has not been bestowed, render it probable that the vicinity of the sea, and the penetration of sea water to the foci of volcanoes, are not absolutely necessary to the eruption of p 246 subterranean fire, and that littoral situations only favor the eruption by forming the margin of a deep sea basin, which, covered by strata of water, and lying many thousand feet lower than the interior continent, can offer but an inconsiderable degree of resistance.

The present active volcanoes, which communicate by permanent craters simultaneously with the interior of the earth and with the atmosphere, must have been formed at a subsequent period, when the upper chalk strta and all the tertiary formations were already present: this is shown to be the fact by the trachytic and basaltic eruptions which frequently form the walls of the crater of elevation. Melaphyres extend to the middle tertiary formations, but are found already in the Jura limestone, where they break through the variegated sandstone.*

We must not confound the earlier outpourings of granite, quartzose porphyry, and euphotide from temporary fissures in the old transition rocks with the present active volcanic craters.

The extinction of volcanic activity is either only partial -- in which case the subterranean fire seeks another passage of escape in the same mountain chain -- or it is total, as in Auvergne. More recent examples are recorded in historical times, of the total extinction of the volcano of Mosychlos,* on the island sacred to Hephaestos (Vulcan), whose "high whirling flames" were known to Sophocles; and of the volcano of Medina, which according to Burckhardt, still continued to pour out a stream of lava on the 2d of November, 1276.

Every stage of volcanic activity, from its first origin to its extinction, is characterized by peculiar products; first by ignited scoriae, streams of lava consisting of trachyte, pyroxene, and obsidian, and by rapilli and tufaceous ashes, accompanied by the development p 247 of large quantities of pure aqueous vapor; subsequently, when the volcano becomes a solfatara, by aqueous vapors mixed with sulphureted hydrogen and carbonic acid gases; and, finally, when it is completely cooled, by exhalations of carbonic acid alone. There is a remarkable class of igneous mountains which do not eject lava, but merely devastating streams of hot water,* impregnated with burning sulphur and rocks reduced to a state of dust (as, for instance, the Galungung in Java); but whether these mountains present a normal condition, or only a certain transitory modification of the volcanic process, must remain undecided until they are visited by geologists possessed of a knowledge of chemistry in its present condition.

I have endeavored in the above remarks to furnish a general description of volcanoes -- comprising one of the most important sections of the history of terrestrial activity -- and I have based my statements partly on my own observations, but more in their general bearing on the results yielded by the labors of my old friend, Leopold von Buch, the greatest geognosist of our own age, and the first who recognized the intimate connection of volcanic phenomena, and their mutual dependence upon one another, considered with reference to their relations in space.

Volcanic action, or the reaction of the interior of a planet on its external crust and surface, was long regarded only as an isolated phenomenon, and was considered solely with respect to the disturbing action of the subterranean force; and it is only in recent times that -- greatly to the advantage of geognostical views based on physical analogies -- volcanic forces have been regarded as 'forming new rocks, and transforming those that already existed'. We here arrive at the point to which I have already alluded, at which a well-grounded study of the activity of volcanoes, whether igneous or merely such as emit gaseous exhalations, leads us, on the one hand, to the mineralogical branch of geognosy (the science of the texture and the succession of terrestrial strata), and, on the other, to the science of geographical forms and outlines -- the configuration of continents and insular groups elevated above the level p 248 of the sea. This extended insight into the connection of natural phenomena is the result of the philosophical direction which has been so generally assumed by the more earnest study of geognosy. Increased cultivation of science and enlargement of political views alike tend to unite elements that had long been divided.

This material taken from pages 248-

COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt

Translated by E C Otte

from the 1858 Harper & Brothers edition of Cosmos, volume 1 --------------------------------------------------

p 248

If, instead of classifying rocks according to their varieties of form and superposition into stratified and unstratified, schistose and compact, normal and abnormal, we investigate those phenomena of formation and transformation which are still going on before our eyes, we shall find that rocks admit of being arranged according to four modes of origin.

'Rocks of eruption', which have issued from the interior of the earth either in a state of fusion from volcanic action, or in a more or less soft, viscous condition, from Plutonic action.

'Sedimentary rocks', which have been precipitated and deposited on the earth's surface from a fluid, in which the most minute particles were either dissolved or held in suspension constituting the greater part of the secondary (or flotz) and tertiary groups.

'Transformed or metamorphic rocks',* in which the internal texture and the mode of stratification have been changed, either p 249 by contact or proximity with a Plutonic or volcanic endogenous rock of eruption,** or, what is more frequently the case, by a gaseous sublimation of substances*** which accompany certain masses erupted in a hot, fluid condition.

'Conglomerates'; coarse or finely granular sandstones, or breccias composed of mechanically-divided masses of the three previous species.

These four modes of formation -- by the emission of volcanic masses, as narrow lava streams; by the action of these masses on rocks previously hardened; by mechanical separation or chemical precipitation from liquids impregnated with carbonic acid; and, finally, by the cementation of disintegrated rocks of heterogeneous nature -- are phenomena and formative processes which must merely be regarded as a faint reflection of that more energetic activity which must have characterized the chaotic condition of the earlier world under wholly different conditions of pressure and at a higher temperature, not only in the whole crust of the earth, but likewise in the more p 250 extended atmosphere, overloaded with vapors. The vast fissures which were formerly open in the solid crust of the earth have since been filled up or closed by the protrusion of elevated mountain chains, or by the penetration of veins of rocks of eruption (granite, porphyry, basalt, and melaphyre); and while, scarcely more than four volcanoes remaining through which fire and stones are erupted, the thinner, more fissured, and unstable crust of the earth was anciently almost every where covered by channels of communication between the fused interior and the external atmosphere. Gaseous emanations rising from very unequal depths, and therefore conveying substances differing in their chemical nature, imparted greater activity to the Plutonic processes of formation and transformation. The sedimentary formations, the deposits of liquid fluids from cold and hot springs, which we daily see producing the travertine strata near Rome, and near Hobart Town in Van Diemen's Land, afford but a faint idea of the flotz formation. In our seas, small banks of limestone, almost equal in hardness at some parts to Carrara marble,* are in the course of formation, by gradual precipitation, accumulation, and cementation -- processes whose mode of action has not been sufficiently well investigated.

The Sicilian coast, the island of Ascension, and King George's Sound in Australia, are instances of this mode of formation. On the coasts of the Antilles, these formations of the present ocean contain articles of pottery, and other objects of human industry, and in Guadaloupe even human skeletons of the Carib tribes.*

The negroes of the French colonies designate these formations by the name of 'Maconne-bon-Dieu'.*

Moreau de Jonnes, 'Hist. Phys. des Antilles', t. i., p. 136, 138, and 543; Humboldt, 'Relation Historique', t. iii., p. 367.

A small colitic bed, formed in Lancerote, one of the Canary Islands, and which, notwithstanding p 251 its recent formation, bears a resemblance to Jura Limestone, has been recognized as a product of the sea and of tempests.*

Composite rocks are definite associations of certain crytonostic, simple minerals, as feldspar, mica, solid silex, augite, and nepheline. Rocks very similar to these consisting of the same elements, but grouped differently, are still formed by volcanic processes, as in the earlier periods of the world. The character of rocks, as we have already remarked is so independent of geographical relations of space,* that the geologist recognizes with surprise, alike to the north or the south of the equator, in the remotest and most dissimilar zones, the familiar aspect, and the repetition of even the most minute characteristics in the periodic stratification of the silurian strata, and in the effects of contact with augitic masses of eruption.

We will now enter more fully into the consideration of the four modes in which rocks are formed -- the four phases of their formative processes manifested in the stratified and unstratified portions of the earth's surface; thus, in the 'endogenous' or 'erupted rocks', designated by modern geognosists as compact and abnormal rocks, we may enumerate the following principal groups as immediate products of terrestrial activity:

1. 'Granite and syenite' of very different respective ages; the granite is frequently the more recent,* traversing the syenite in veins, and being, in that case, the active upheaving agent. "Where the granite occurs in large, insulated masses of a faintly-arched, ellipsoidal form, it is covered by a crust of shell cleft into blocks, instances of which are met with alike in the Hartz district, in Mysore, and in Lower Peru.

This surface of the granite, owing to the great expansion that accompanied its first upheaval."*

Both in Northern Asia,* on the charming and romantic shores of the Lake of Kolivan, on the northwest declivity of p. 252 the Altai Mountains, and at Las Trincheras, on the slop of the littoral chain of Caraccas,** I have seen granite divided into ledges, owing probably to a similar contraction, although the divisions appeared to penetrate far into the interior.

Further to the south of Lake Kolivan, toward the boundaries of the Chinese province Ili (between Buchtarminsk and the River Narym), the formation of the erupted rock, in which there is no gneiss, is more remarkable than I ever observed in any other part of the earth. The granite, which is always covered with scales and characterized by tabular divisions, rises in the steppes, either in small hemispherical eminences, scarcely six or eight feet in height, or like basalt, in mounds, terminating on either side of their bases in narrow streams.*

At the cataracts of the Orinoco, as well as in the district of the Fichtelgebirge (Seissen), in Galicia, and between the Pacific and the highlands of Mexico (on the Papagallo), I have seen granite in large, flattened spherical masses, which could be divided, like basalt, into concentric layers. In the valley of Irtysch, between Buchtarminsk and Ustkamenogorsk, granite covers transition slate for a space of four miles,* penetrating into it from above in narrow, variously ramified, wedge-like veins.

I have only instanced these peculiarities in order to designate the individual character of one of the most generally diffused erupted-rocks. As granite is superposed on slate in Siberia and in the Departement de Finisterre (Isle de Mihau), so it covers the Jura limestone in the mountains of Oisons (Fermonts), and syenite, and indirectly also chalk, in Saxony, near Weinbohla.*

Near Mursinsk, in the Uralian district, granite is of a drusous character, and here the pores, like the fissures and cavities of recent volcanic products, inclose many kinds of magnificent crystals, especially beryls and topazes.

2. 'Quartzose porphyry' is often found in the relation of veins to other rocks. The base is generally a finely granular mixture of the same elements which occur in the larger imbedded p 253 crystals. In granitic porphyry that is very poor in quartz, the feldspathic base is almost granular and laminated.*

3. 'Greenstones, Diorite', are granular mixtures of white albite and blackish-green hornblende, forming dioritic porphyry when the crystals are deposited in a base of denser tissue. The greenstones, either pure, or inclosing laminae of diallage (as in the Fichtelgebirge), and passing into serpentine, have sometimes penetrated, in the form of strata, into the old stratified fissures of green argillaceous slate, but they more frequently traverse the rocks in veins, or appear as globular masses of greenstone, similar to domes of basalt and porphyry.*

'Hypersthene rock' is a granular mixture of labradorite and hypersthene.

'Euphotide' and serpentine, containing sometimes crystald of augite and uralite instead of diallage, are thus nearly allied to another more frequent, and I might almost say, more 'energetic' eruptive rock -- augitic porphyry.*

'Melaphyre', augitic, uralitic, and oligoklastic porphyries. To the last-named species belongs the genuine 'verd-antique', so celebrated in the arts.

'Basalt', containing olivine and constituents which gelatinize in acids; phonolithe (porphyritic slate), trachyte, and colerite; the first of these rocks is only paartially, and the second always, divided into thin laminae, which give them an appearance of stratification when extended over a large space. Mesotype and nepheline constitute, according to Girard, an important part in the composition and internal texture of basalt. The nepheline contained in basalt reminds the geognosist both of the miascite of the Ilmen Mountains in the Ural,* which has been confounded with granite, and sometimes contains zirconium, and of the pyroxenic nepheline discovered by Gumprecht near Lobau and Chemnitz.

To the second or sedimentary rocks belong the greater part of the formations which have been comprised under the old p 254 systematic, but not very correct designation of 'transition, flot' or 'secondary', and 'tertiary formations'. If the erupted rocks had not exercised an elevating, and, owing to the simultaneous shock of the earth, a disturbing influence on these sedimentary formations, the surface of our planet would have consisted of strata arranged in a uniformly horizontal direction above one another. Deprived of mountain chains, on whose declivities the gradations of vegetable forms and the scale of the diminishing heat of the atmosphere appear to be picturesquely reflected -- furrowed ony here and there by valleys of erosion, formed by the force of fresh water moving on in gentle undulations, or by the accumulation of detritus, resulting from the action of currents of water -- continents would have presented no other appearance from pole to pole than the dreary uniformity of the llanos of South America or the steppes of Northern Asia. The vault of heaven would everywhere have appeared to rest on vast plains, and the stars to rise as if they emerged from the depths of ocean. Such a condition of things could not, however, have generally prevailed for any length of time in the earlier periods of the world, since subterranean forces must have striven in all epochs to exert a counteracting influence.

Sedimentary strta have been either precipitated or deposited from liquids, according as the materials entering into their composition are supposed, whether as limestone or argillaceous slate, to be either chemically dissolved or suspended and commingled. But earth, when dissolved in fluids impregnated with carbonic acid, must be regarded as undergoing a mechanical process while they are being precipitated, deposited, and accumulated into strata. This view is of some importance with respect to the envelopment of organic bodies in petrifying calcareous beds. The most ancient sediments of the transition and secondary formations have probably been formed from water at a more or less high temperature, and at a time when the heat of the upper surface of the earth was still very considerable. Considered in this point of view, a Plutonic action seems to a certain extent also to have taken place in the sedimentary strata, especially the more ancient; but these strata appear to have been hardened into a schistose structure, and under great pressure, and not to have been solidified by cooling, like the rocks that have issued from the interior, as, for instance, granite, porphyry, and basalt. By degrees, as the waters lost their temperature, and were able to absorb a copious supply of the carbonic acid gas with which p 255 the atmosphere was overcharged, they became fitted to hold in solution a larger quantity of lime.

'The sedimentary strata', setting aside all other exogenous, purely mechanical deposits of sand or detritus, are as follows:

'Schist', of the lower and upper transition rock, compositing the silurian and devonian formations; from the lower silurian strata, which were once termed cambrian, to the upper strata of the old red sandstone or devonian formation, immediately in contact with the mountain limestone.

'Carboniferous deposits':

'Limestones' imbedded in the transition and carboniferous formations; zechstein, muschelkalk, Jura formation and chalk, also that portion of the tertiary formation which is not included in sandstone and conflomerate.

'Travertine', fresh-water limestone, and silicious concretions of hot springs, formations which have not been produced under the pressure of a large body of sea water, but almost in immediate contact with the atmosphere, as in shallow marshes and streams.

'Infusorial deposits': geognostical phenomena, whose great importance in proving the influence of organic activity in the formation of the solid part of the earth's crust was first discovered at a recent period by my highly-gifted friend and fellow-traveler, Ehrenberg.

If, in this short and superficial view of the mineral constituents of the earth's crust, I do not place immediately after the simple sedimentary rocks the conglomerates and sandstone formations which have also been deposited as sedimentary strata from liquids, and which have been imbedded alternately with schist and limestone, it is only because they contain, together with the detritus of eruptive and sedimentary rocks, also the detritus of gneiss, mica slate, and other metamorphic masses. The obscure process of this metamorphism, and the action if produces, must therefore compose the third class of the fundamental forms of rock.

Endogenous or erupted rocks (granite, porphyry, and melaphyre) produce, as I have already frequently remarked, not only cynamical, shaking, upheaving actions, either vertically or laterally displacing the strata, but they also occasion changes in their chemical composition as well as in the nature of their internal structure; new rocks being thus formed, as gneiss, mica slate, and granular limestone (Carrara and Parian marble). The old silurian or devonian transition schists, the belemnitic limestone of Tarantaise, and the dull gray calcareous p 256 sandstone ('Macigno'), which contains alggae found in the northern Apennines, often assume a new and more brilliant appearance after their metamorphosis, which renders it difficult to recognize them. The theory of metamorphism was not established until the individual phases of the change were followed step by step, and direct chemical experiments on the difference in the fusion point, in the pressure and time of cooling, were brought in aid of mere inductive conclusions. Where the study of chemical combinations is regulated by leading ideas,* it may be the means of throwing a clear light on the wide field of geognosy, and over the vast laboratory of nature in which rocks are continually being formed and modified by the agency of subterranean forces.

The philosopohical inquirer will escape the deception of apparent analogies, and the danger of being led astray by a narrow view of natural phenomena, if he constantly bear in view the complicated conditions which may, by the intensity of their force, have modified the counteracting effect of those individual substances whose nature is better known to us. Simple bodies have, no doubt, at all periods, obeyed the same laws of attraction, and, wherever apparent contradictions present themselves, I am confident that chemistry will in most cases be able to trace the cause to some corresponding error in the experiment.

Observations made with extreme accuracy over large tracts of land, show that erupted rocks have not been produced in an irregular and unsystematic manner. In parts of the globe most remote from one another, we often find that granite, basalt, and diorite have exercised a regular and uniform metamorphic action, even in the minutest details, on the strata of argillaceous slate, dense limestone, and the grains of quartz in sandstones. As the same endogenous rock manifests almost every where the same degree of activity, so on the contrary, different rocks belonging to the same class, whether to the endogenous or the erupted, exhibit great differences in their character. Intense heat has undoubtedly influenced all these phenomena, but the degree of fluidity (the more or less perfect mobility of the particles -- their more viscous composition) has varied very considerably from the granite to the basalt, while at different geological p 257 periods (or metamorphic phases of the earth's crust) other substances dissolved in vapors have issued from the interior of the earth simultaneously with the eruption of granite, basalt, greenstone porphyry, and serpentine. This seems a fitting place again to draw attention to the fact that, according to the admirable views of modern geognosy, the metamorphism of rocks is not a mere phenomenon of contact, limited to the effect produced by the apposition of two rocks, since it comprehends all the generic phenomena that have accompanied the appearance of a particular erupted mass. Even where there is no immediate contact, the proximity of such a mass gives rise to modifications of solidification, cohesion, granulation, and crystallization.

All eruptive rocks penetrate, as ramifying veins either into the sedimentary strata, or into other equally endogenous masses; but there is a special importance to be attached to the difference manifested between 'Plutonic' rocks* (granite, porphyry, and serpentine) and those termed 'volcanic' in the strict sense of the word (as trachyte, basalt, and lava).

The rocks produced by the activity of our present volcanoes appear as band-like streams, but by the confluence of several of them they may form an extended basin. Wherever it has been possible to trace basaltic eruptions, they have generally been found to terminate in slender threads. Examples of these narrow openings may be found in three places in Germany: in the 'Pflaster-kaute', at Marksuhl, eight miles from Eisenach; in the blue 'Kuppe', near Eschwege, on the banks of the Werra; and in the Druidical stone on the Hollert road (Siegen), where the basalt has broken through the variegated sandstone and graywacke slate, and has spread itself into cup-like fungoid enlargements, which are either grouped together like rows of columns, or are sometimes stratified in thin laminae. The case is otherwise with granite, syenite, quartzose porphyry, serpentine, and the whole series of unstratified compact rocks, to which, from a predilection for a mythological nomenclature, the term Plutonic has been applied. These, with the exception of occasional veins, were probably not erupted in a state of fusion, but merely in a softened condition; not from narrow fissures, but from long and widely-extending gorges. They have been protruded, but have not flowed forth, and are found not in streams like lava, but in extended masses.*

Some groups of dolerite and trachyte indicate p 258 a certain degree of basaltic fluidity; others, which have been expanded into vast craterless domes, appear to have been only in a softened condition at the time of their elevation. Other trachytes, like those of the Andes, in which I have frequently perceived a striking analogy with the greenstones and syenitic porphyries (which are argentiferous, and without quartz), are deposited in the same manner as granite and quartzose porphyry.

Experiments on the changes which the texture and chemical constitution of rocks experience from the action of heat, have shown that volcanic masses* (diorite, augitic porphyry, basalt, and the lava of AEtna) yield different products, according to the difference of the pressure under which they have been fused, and the length of time occupied during their cooling; thus, where the cooling was rapid, they form a black glass, having a homogeneous fracture, and where the cooling was slow, a stony mass of granular crystalline structure.

In the latter case, the crystals are formed partly in cavities and partly inclosed in the matrix. The same materials yield the most dissimilar products, a fact that is of the greatest importance in reference to the study of the nature of erupted rocks, and of the metamorphic action which they occasion. Carbonate of lime, when fused under great pressure, does not lose its carbonic acid, but becomes, when cooled, granular limestone; when the crystallization has been effected by the dry method, saccharoidal marble; while by the humid method, calcareous spar and aragonite and produced, the former under a lesser degree of temperature than the latter.*

Differences of temperature p 259 likewise modify the direction in which the different particles arrange themselves in the act of crystallization, and also affect the form of the crystal.*

Even when a body is not in a fluid condition, the smallest particles may undergo certain relations in their various modes of arrangement, which are manifested by the different action on light.*

The phenomena presented by devitrification, and by the formation of steel by cementation and casting -- the transition of the fibrous in the granular tissue of the iron, from the action of heat* and probably, also, by regular and long-continued concussions -- likewise throw a considerable degree of light on the geological process of metamorphism.

Heat may even simultaneously induce opposite actions in crystalline bodies; for the admirable experiments of Mitscherlich have established the fact* that calcareous spar, without altering its condition of aggregation, expands in the direction of one of its axes and contracts in the other.

If we pass from these general considerations to individual examples, we find that schist is converted, by the vicinity of Plutonic erupted rocks, into a bluish-black, glistening roofing slate. Here the planes of stratification are intersected by another system of divisional stratification, almost at right angles with the former,* and thus indicating an action subsequent to the alteration.

The penetration of silica causes the argillaceous schist to be traversed by quartz, transforming it, in part, into whetstone and silicious schist; the latter sometimes containing carbon, and being then capable of producing galvanic effects on the nerves. The highest degree of silicifaction of schist is that observed in ribbon jasper, a material highly valuable in the arts,* and which is produced in the Oural Mountains p 260 by the contact and eruption of augitic porphyry (at Orsk), of dioritic porphyry (at Aufschkul), or of a mass of hypersthenic rock conglomerated into spherical masses (at Bogoslowsk). At Monte Serrato, in the island of Elba, according to Frederic Hoffman, and in Tuscany, according to Alexander Brongniart, it is formed by contact with euphotide and serpentine.

The contact and Plutonic action of granite have sometimes made argillaceous schist granular, as was observed by Gustav Rose and myself in the Altai Mountains (within the fortress of Buchtarminsk),* and have transformed it into a mass resembling granite, consisting of a mixture of feldspar and mica, in which larger laminae of the latter were again imbedded.**

Most geognosists adhere, with Leopold von Buch, to the well-known hypothesis "that all the gneiss in the silurian strata of the transition formation, between the Icy Sea and the Gulf of Finland, has been produced by the metamorphic action of granite.*

In the Alps, at St. Gothard, calcareous marl is likewise changed from granite into mica slate, and then transformed into gneiss." Similar phenomena of the formation of gneiss and mica slate through granite present themselves in the oolitic group of the Tarantaise,* in which belemnites are p 261 found in rocks, which have some claim to be considered as mica slate, and in the schistose group in the western part of the island of Elba, near the promontory of Calamita, and the Fichtelgebirge in Baireuth, between Loomitz and Markleiten.**

Jasper, which,* as I have already remarked, is a production formed by the volcanic action of augitic porphyry, could only be obtained in small quantities by the ancients, while another material, very generally and efficiently used by them in the arts, was granular or saccharoidal marble, which is likewise to be regarded solely as a sedimentary stratum altered by terrestrial heat and by proximity with erupted rocks.

This opinion is corroborated by the accurate observations on the phenomena of contact, by the remarkable experiments on fusion p 262 made by Sir James Hall more than half a century ago, and by the attentive study of granitic veins, which has contributed so largely to the establishment of modern geognosy. Sometimes the erupted rock has not transformed the compact into granular limestone to any great depth from the point of contact. Thus, for instance, we meet with a slight transformation -- a penumbra -- as at Belfast, in Ireland, where the basaltic veins traverse the chalk, and, as in the compact calcareous beds, which have been partially inflected by the contact of syenitic granite, at the Bridge of Boscampo and the Cascade of Conzocoli, in the Tyrol (rendered celebrated by the mention made of it by Count Mazari Peucati).*

Another mode of transformation occurs where all the strata of the compact limestone have been changed into granular limestone by the action of granite, and syenitic or dioritic porphyry.*

I would here wish to make special mention of Parian and Carrara marbles, which have acquired such celebrity from the noble works of art into which they have been converted, and which have too long been considered in our geognostic collections as the main types of primitive limestone. The action of granite has been manifested sometimes by immediate contact, as in the Pyrenees,* and sometimes, as in the main land of Greece, and in the insular groups in the gean Sea, through the intermediate layers of gneiss or mica slate.

Both cases presuppose a simultaneous but heterogeneous process of transformation. p 263 In Attica, in the island of Euboea, and in the Peloponnesus, it has been remarked, "that the limestone, when superposed on mica slate, is beautiful and crystalline in proportion to the purity of the latter substance and to the smallness of its argillaceous contents; and, as is well known, this rock, together with beds of gneiss, appears at many points, at a considerable depth below the surface, in the islands of Paros and Antiparos."*

We may here infer the existence of an imperfectly metamorphosed flotz formation, if faith can be yielded to the testimony of Origen, according to whom, the ancient Eleatic, Xenophanes of Colophon* (who supposed the whole earth's crust to have been once covered by the sea), declared that marine fossils had been found in the quarries of Syracuse, and the impression of a fish (a sardine) in the deepest rocks of Paros.

The Carrara or Luna marble quarries, which constituted the principal source from which statuary marble was derived even prior to the time of Augustus, and which will probably continue to do so until the quarries of Paros shall be reopened, are beds of calcareous sandstone -- macigno -- altered by Plutonic action, and occurring in the insulated mountain of Apuana, between gneiss-like mica and talcose schist.*

Whether at some points granular limestone may not have been formed in the interior of the earth, and been raised by gneiss and syenite to the surface, where it forms vein-like fissures,* is a question on which I can not hazard an opinion, owing to my own want of personal knowledge of the subject.

p 264 According to the admirable observations of Leopold von Buch, the masses of dolomite found in Southern Tyrol, and on the Italian side of the Alps, present the most remarkable instance of metamorphism produced by massive eruptive rocks on compact calcareous beds. The formation of the limestone seems to have proceeded from the fissures which traverse it in all directions. The cavities are every where covered with rhomboidal crystals of magnesian bitter spar, and the whole formation, without any trace of strtification, or of the fossil remains which it once contained, consists only of a granular aggregation of crystals of dolomite. Talc laminae lie scattered here and there in the newly-formed rock, traversed by masses of serpentine. In the valley of the Fassa, dolomite rises perpendicularly in smooth walls of dazzling whiteness to a height of many thousand feet. It forms sharply-pointed conical mountains, clustered together in large numbers, but yet not in contact with each other. The contour of their forms recalls to mind the beautiful landscape with which the rich imagination of Leonardi da Vinci has embellished the back-ground of the portrait of Mona Lisa.

The geognostic phenomena which we are now describing, and which excite the imagination as well as the powers of the intellect, are the result of the action of augite porphyry manifested in its elevating, destroying, and transforming force.*

The process by which limestone is converted into dolomite is not regarded by the illustrious investigator who first drew attention to the phenomenon as the consequence of the tale being derived from the black porphyry, but rather as a transformatiion simultaneous with the appearance of this erupted stone through wide fissures filled with vapors. It remains for future inquirers to determine how transformation can have been effected without contact with the endogenous stone, where strata of dolomite are found to be interspersed in imestone. Where, in this case, are we to seek the concealed channels by which the Plutonic action is conveyed? Even here it may not, however, be necessary, in conformity with the old Roman adage, to believe "that much that is alike in nature may have been formed in wholly different ways." When we find, over widely extended parts of the earth, that two phenomena are always associated together, as, for instance, the occurrence of melaphyre p 265 and the transformation of compact limestone into a crystaline mass differing in its chemical character, we are, to a certain degree, justified in believing, where the second phenomenon is manifested unattended by the appearance of the first, that this apparent contradiction is owing to the absence, in certain cases, of some of the conditions attendant upon the exciting causes. Who would call in question the volcanic nature and igneous fluidity of basalt merely because there are some rare instances in which basaltic veins, traversing beds of coal or strata of sandstone and chalk, have not materially deprived the coal of its carbon, nor broken and slacked the sandstone, not converted the chalk into granular marble? Wherever we have obtained even a faint light to guide us in the obscure domain of mineral formation, we ought not ungratefully to disregard it, because there may be much that is still unexplained in the history of the relations of the transitions, or in the isolated interposition of beds of unaltered strata.

After having spoken of the alteration of compact carbonate of lime into granular limestone and dolomite, it still remains for us to mention a third mode of transformation of the same mineral, which is ascribed to the emission, in the ancient periods of the world, of the vapors of sulphuric acid. This transformation of limestone into gypsum is analogous to the penetration of rock salt and sulphur, the latter being deposited from sulphureted aqueous vapor. In the lofty Cordilleras of Quindin, far from all volcanoes, I have observed deposits of sulphur in fissures in gneiss, while in Sicily (at Cattolica, near Girgenti), sulphur, gypsum, and rock salt belong to the most recent secondary strata, the chalk formations.*

I have also seen on the edge of the crater of Vesuvius, fissures filled with rock salt, which occurred in such considerable masses as occasionally to lead to its being disposed of by contraband trade. On both declivities of the Pyrenees, the connection of diorite and pyroxene, and colomite, gypsum, and rock salt, can not be questioned;* and here, as in the other phenomena which we have been considering, every thing bears evidence of the action of subterranean forces on the sedimentary strata of the ancient sea.

There is much difficulty in explaining the origin of the beds of pure quartz, which occur in such large quantities in South America, and impart so peculiar a character to the chain of p 266 the Andes.*

In descending toward the South Sea, from Caxamarca toward Guangamarca, I have observed vast masses of quartz, from 7000 to 8000 feet in height, superposed sometimes on porphyry devoid of quartz, and sometimes on diorite. Can these beds have been transformed from sandstone, as Elie de Beaumont conjectures in the case of the quartz strata on the Col de la Poissonniere, east of Briançon?*

In the Brazils, in the diamond district of Minas Geraes and St. Paul, which has recently been so accurately investigated by Clausen, Plutonic action has developed in dioritic veins sometimes ordinary mica, and sometimes specular iron in quartzose itacolumite. The diamonds of Grammagoa are imbedded in strata of solid silica, and are occasionally enveloped in laminae of mica, like the garnets found in mica slate. The diamonds that occur furthest to the north, as those discovered in 1829 at 58 degrees lat., on the European slope of the Uralian Mountains, bear a geognostic relation to the black carboniferous dolomite of Adolffskoi* and to augitic porphyry, although more accurate observations are required in order fully to elucidate this subject.

Among the most remarkable phenomena of contact, we must, finally, enumerate the formation of garnets in argillaceous schist in contact with basalt and dolerite (as in Northumberland and the island of Anglesea), and the occurrence of a vast number of beautiful and most various crystals, as garnets, vesuvian, augite, and ceylanite, on the surfaces of contact between the erupted and sedimentary rock, as, for instance, on the junction of the syenite of Monzon with dolomite and compact limestone.

In the island of Elba, masses of serpentine, which perhaps nowhere more clearly indicate the character of erupted rocks, have occasioned the sublimation of iron glance and red oxyd of iron in fissures of calcareous sandstone.

We still daily find the same iron glance formed by sublimation from the vapors and the walls of the fissures of open veins on the margin of the crater, and in the fresh lava currents of the volcanoes of Stromboli, Vesuvius, and AEtna.*

The veins that p 267 are thus formed beneath our eyes by volcanic forces, where the contiguous rock has already attained a certain degree of solidification, show us how, in a similar manner, mineral and metallic veins may have been every where formed in the more ancient periods of the world, where the solid but thinner crust of our planet, shaken by earthquakes, and rent and fissured by the change of volume to which it was subjected in cooling, may have presented many communications with the interior, and many passages for the escape of vapors impregnated with earthy and metallic substances. The arrangement of the particles in layers parallel with the margins of the beins, the regular recurrence of analogous layers on the opposite sides of the veins (on their different walls), and, finally, the elongated cellular cavities in the middle, frequently afford direct evidence of the Plutonic process of sublimation in metalliferous veins. As the traversing rocks must be of more recent origin than the traversed, we learn from the relations of stratification existing between the porphyry and the argentiferous ores in the Saxon mines (the richest and most important in Germany), that these formations are at any rate more recent than the vegetable remains found in carboniferous strata and in the red sandstone.*

All the facts connected with our geological hypotheses on the formation of the earth's crust and the metamorphism of rocks have been unexpectedly elucidated by the ingenious idea which led to a comparison of the slags or scoriae of our smelting furnaces with natural minerals, and to the attempt of reproducing the latter from their elements.*

In all these operations, the same affinities manifest themselves which determine chemical combinations both in our laboratories and in the interior of the earth. The most considerable part of p 268 the simple minerals which characterize the more generally diffused Plutonic and erupted rocks, as well as those on which they have exercised a metamorphic action, have been produced in a crystalline state, and with perfect identify, in artificial mineral products. We must, however, distinguish here between the scoriae accidentally formed, and those which have been designedly produced by chemists. To the former belong feldspar, mica, augite, olivine, hornblende, crystallized oxyd of iron, magnetic iron in octahedral crystals, and metallis titanium;* to the latter, garnets, idocrase, rubies (equal in hardness to those found in the East), olivine, and augite.**

These minerals constitute the main constituents of granite, gneiss, and mica schist, of basalt, dolerite, and many porphyries. The artificial production of feldspar and mica is of most especial geognostic importance with reference to the theory of the formation of gneiss by the metamorphic agency of argillaceous schist, which contains all the constituents of granite, p 269 potash not excepted.*

It would not be very surprising, therefore, as is well observed by the distinguished geognosist, Von Dechen, if we were to meet with a fragment of gneiss formed on the walls of a smelting furnace which was built of argillaceous slate and graywacke.

After having taken this general view of the three classes of erupted, sedimentary, and metamorphic rocks of the earth's crust, it still remains for us to consider the fourth class, comprising 'conglomerates', or 'rocks of detrius'. The very term recalls the destruction which the earth's crust has suffered, and likewise, perhaps reminds us of the process of cementation, which has connected together, by means of oxyd of iron, or of some argillaceous and calcareous substances, the sometimes rounded and sometimes angular portions of fragments. Conglomerates and rocks of detritus, when considered in the widest sense of the term, manifest characters of a double origin. The substances which enter into their mechanical composition have not been alone accumulated by the action of the waves of the sea or currents of fresh water, for there are some of these rocks the formation of which can not be attributed to the action of water. "When basaltic islands and trachytic rocks rise on fissures, friction of the elevated rock against the walls of the fissures causes the elevated rock to be inclosed by conglomerates composed of its own matter. The granules composing the sandstones of many formations have been separated rather by friction against the erupted volcanic or Plutonic rock than destroyed by the erosive force of a neighboring sea. The existence of these friction 'conglomerates', which are met with in enormous masses in both hemispheres, testifies the intensity of the force with which the erupted rocks have been propelled from the interior through the earth's crust. This detritus has subsequently been taken up by the waters, which have then deposited it in the strata which it still covers."*

Sandstone formations are found imbedded in all strata, from the lower silurian transition stone to the beds of the tertiary formations, superposed on the chalk. They are found on the margin of the boundless plains of the New Continent, both within and without the tropics, extending like breast-works along the ancient shore, against which the sea once broke its foaming waves.

p 270 If we cast a glance on the geographical distribution of rocks, and their relations in space, in that portion of the earth's crust which is accessible to us, we shall find that the most universally distributed chemical substance is 'silicic acid', generally in a variously-colored and opaque form. Next to solid silicic acid we must reckon carbonate of lime, and then the combinations of silicic acid with alumina, potash, and soda, with lime, magnesia, and oxyd of iron.

The substances which we designate as 'rocks' are determinate associations of a small number of minerals, in which some combine parasitically, as it were, with others, but only under definite relations; thus, for instance, although quartz (silica), feldspar, and mica are the principal constituents of granite, these minerals also occur, either individually or collectively, in many other formations. By way of illustrating how the quantitative relations of one feldspathic rock differ from another, richer in mica than the former, I would mention that, according to Mitscherlich, three times more alumina and one third more silica than that ossessed by feldspar, give the constituents that enter into the composition of mica. Potash is contained in both -- a substance whose existence in many kinds of rocks is probably antecedent to the dawn of vegetation on the earth's surface.

The order of succession, and the relative age of the different formations, may be recognized by the superposition of the sedimentary, metamorphic, and conglomerate strata; by the nature of the formations traversed by the erupted masses, and -- with the greatest certainty -- by the presence of organic remains and the differences of their structure. The application of botanical and zoological evidence to determine the relative age of rocks -- this chronometry of the earth's surface, which was already present to the lofty mind of Hooke -- indicates one of the most glorious epochs of modern geognosy, which has finally, on the Continent at least, been emancipated from the sway of Semitic doctrines. Palaeontological investigations have imparted a vivifying breath of grace and diversity to the science of the solid structure of the earth.

The fossiliferous strata contain, entombed within them, the floras and faunas of by-gone ages. We ascend the stream of time, as in our study of the relations of superposition we descend deeper and deeper through the different strata, in which lies revealed before us a past world of animal and vegetable life. Far-extending disturbances, the elevation of great mountain chains, whose relative ages we are able to define, attest the p 271 destruction of ancient and the manifestation of recent organisms. A few of these older structures have remained in the midst of more recent species. Owing to the limited nature of our knowledge of existence, and from the figurative terms by which we seek to hide our ignorance, we apply the appellation 'recent structure' to the historical henomena of transition manifested in the organisms as well as in the forms of primitive seas and of elevated lands. In some cases these organized structures have been preserved perfect in the minutest details of tissues, integument, and articulated parts, while in others, the animal, passing over soft argillaceous mud, has left nothing but the traces of its course,* or the remains of its undigested food, as in the coprolites.**

In the lower Jura formations (the lias of Lyme Regis), the ink bag of the sepia has been so wonderfully preserved, that the material, which myriads p 272 of years ago might have served the animal to conceal itself from its enemies, still yields the color with which its image may be drawn.*

In other strata, again, nothing remains but the faint impression of a muscle shell; but even this, if it belong to a main dividion of mollusca,* may serve to show the traveler, in some distant land, the nature of the rock in which it is found, and the organic remains with which it is associated.

Its discovery gives the history of the country in which it occurs.

The analytic study of primitive animal and vegetable life has taken a double direction: the one is purely morphological, and embraces, especially, the natural history and physiology of organisms, filling up the chasms in the series of still living species by the fossil structures of the primitive world. The second is more specially geognostic, considering fossil remains in their relations to the superposition and relative age of the sedimentary formations. The former has long predominated over the latter, and an imperfect and superficial comparison of fossil remains with existing species has led to errors, which may still be traced in the extraordinary names applied to certain natural bodies. It was sought to identify all fossil species with those still extant in the same manner as, in the sixteenth century, men were led by false analogies to compare the animals of the New Continent with those of the Old. Peter Camper, Sommering, and Blumenbach had the merit of being the first, by the scientific application of a more accurate p 273 comparative anatomy, to throw light on the osteological branch of palaeontology -- the archaeology of organic life; but the actual geognostic views of the doctrine of fossil remains, the felicitous combination of the zoological character with the order of succession, and the relative ages of strata, are due to the labors of George Cuvier and Alexander Brongniart.

The ancient sedimentary formations and those of transition rocks exhibit, in the organic remains contained within them, a mixture of structures very variously situated on the scale of progressively-developed organisms. These strata contain but few plants, as, for instance, some species of Fuci, Lycopodiaceae which were probably arborescent, Equisetaceae, and tropical ferns; they present, however, a singular association of animal forms, consisting of Crustacea (trilobites with reticulated eyes, and Calymene), Brachiopoda ('Spirifer, Orthis'), elegant Sphaeronites, nearly allied to the Crinoidea,* Orthoceraitites, of the family of the Cephalopoda, corals, and, blended with these low organisms, fishes of the most singular forms, imbedded in the upper silurian formations.

The family of the Cephalaspides, whose fragments of the species 'Pterichtys' were long held to be trilobites, belongs exclusively to the devonian period (the old red), manifesting, according to Agassiz, as peculiar a type among fishes as do the Ichthyosauri and Plesiosauri among reptiles.*

The Goniatites, of the tribe of Ammonites,* a are manifested in the transition chalk, in the graywacke of the devonian periods, and even in the latest silurian formations.

The dependence of physiological gradation upon the age of the formations, which has not hitherto been shown with perfect certainty in the case of invertebrata,* is most regularly manifested in vertebrated animals.

The most ancient of these, as we have already seen, are fishes; next in the order of succession of formation, passing from the lower to the upper, come reptiles and mammalia. The first reptile (a Saurian, the Monitor of Cuvier), which excited the attention of Leibnitz,* is found in cuperiferous schist of the Zechstein of Thuringa; the Palaeosaurus and Thecodontosaurus of Bristol are, according to Murchison, of the same age.

The Saurians are found in large numbers in the muschelkalk,* in the keuper, and in the oolitic formations, where they are the most numerous.

At the period of these formations there existed Pleiosauri, having long, swan-like necks consisting of thirty vertebrae; Megalosauri, monsters resembling the crocodile, forty-five feet in length, and having feet whose bones were like those of terrestrial mammalia, eight species of large-eyed Ichthyosauri, the Geosaurus or 'Lacerta gigantea', of Sommering, and finally, seven remarkable species of Pterodactyles,* of Saurians furnished with membranous wings.

In the chalk the number of the crocodilial Saurians diminishes, although this epoch is characterized by the so-called crocodile of Maestricht (the Mososaurus of Conybeare), and the colossal, probably graminivorous Iguandon. Cuvier has found animals belonging to the existing families of the crocodile in the tertiary formation, and Scheuchzer's 'antediluvian man' ('homo diluvii testis'), a large salamander allied to the Axolotl, which I brought with me from the large Mexican lakes, belongs to the most recent fresh-water formations of Oeningen.*

The determination of the relative ages of organisms by the superposition of the strata has led to important results regarding the relations which have been discovered between extinct families and species (the latter being but few in number) and those which still exist. Ancient and modern observations concur in showing that the fossil floras and faunas differ more from the present vegetable and animal forms in proportion as they belong to lower, that is, more ancient sedimentary formations. The numerical relations first deduced by Cuvier p 275 from the great phenomena of the metamorphism of organic life,* have led, through the admirable labors of Deshayes and Lyell, to the most marked results, especially with reference to the different groups of the tertiary formations, which contain a considerable number of accurately investigated structures.

Agassiz, who has examined 1700 species of fossil fishes, and who estimates the number of living species which have either been described or are preserved in museums at 8000, expressly says, in his masterly work, that, "with the exception of a few small fossil fishes peculiar to the argillaceous geodes of Greenland, he has not found any animal of this class in all the transition, secondary or tertiary formations, which is specifically identical with any still extant fish." He subjoins the important observation "that in the lower tertiary formations, for instance, in the coarse granular calcareous beds, and in the London clay,* one third of the fossil fishes belong to wholly extinct families.

Not a single species of a still extant family is to be found under the chalk, while the remarkable family of the 'Sauroidi' (fishes with enameled scales), almost allied to reptiles, and which are found from the coal beds -- in which the larger species lie -- to the chalk, where they occur individually, bear the same relation to the two families (the Lepidosteus and Polypterus) which inhabit the American rivers and the Nile, as our present elephants and tapirs do to the Mastodon and Anaplotheriun of the primitive world."*

The beds of chalk which contain two of these sauroid fishes and gigantic reptiles, and a whole extinct world of corals and muscles, have been proved by Ehrenberg's beautiful discoveries to consist of microscopic Polythalamia, many of which still exist in our seas, and in the middle latitudes of the North Sea and Baltic. The first group of tertiary formations above the chalk, which has been designated as belonging to the 'Eocene Period', does not, therefore, merit that designation, since "the 'dawn of the world' in which we live extends much further back in the history of the past than we have hitherto supposed."*

As we have already seen, fishes, which are the most ancient of all vertebrata, are found in the silurian transition strata, p 276 and then uninterruptedly on through all formations to the strata of the tertiary period, while Saurians begin with the zechstone. In like manner, we find the first mammalia ('Thylacotherium Prevostii', and 'T. Bucklandii', which are nearly allied according to Valenciennes,* with marsupial animals) in the oolitic formations (Stonesfield schist), and the first birds in the most ancient cretaceous strata.**

Such are, according to the present state of our knowledge, the lowest* limits of fishes, Saurians, mammalia, and birds.

Although corals and Serpulidae occur in the most ancient formations simultaneously with highly-developed Cephalopodes and Crustaceans, thus exhibiting the most various orders grouped together, we yet discover very determinate laws in the case of many individual groups of one and the same orders. A single species of fossil, as Goniatites, Trilobites, or Nummulites, sometimes constitutes whole mountains. Where different families are blended together, a determinate succession of organisms has not only been observed with reference to the superposition of the formations, but the association of certain families and species has also been noticed in the lower strata of the same formation. By his acute discovery of the arrangement of the lobes of their chamber-sutures, Leopold von Buch has been enabled to divide the innumerable quantity of Ammonites into well-characterized families, and to show that Ceratites appertain to the muschelkalk, Arietes to the lias, and Goniatites to transition limestone and graywacke.*

The lower limits of Belemnites are, in the keuper, covered by Jura limestone, and their upper limits in the chalk formations.*

It appears, from what we now know of this subject, that the waters must have been inhabited at the same epoch, and in the most widely-remote districts of the world, by shell-fish, which were at any rate, in part, identical with the fossil remains found in England. Leopold von Buch has discovered exogyra and trigonia in the southern hemisphere (volcano of p 277 Maypo in Chili), and D'Orbigny has described Ammonites and Gryphites from the Himalaya and the Indian plains of Cutch, these remains being identical with those found in the old Jurassic sea of Germany and France.

The strata which are distinguished by definite kinds of petrifacations, or by the fragments contained within them, form a geognostic horizon, by which the inquirer may guide his steps, and arrive at certain conclusions regarding the identity or relative age of the formations, the periodic recurrence of certain strata, their parallelism, or their total suppression. If certain strata, their parallelism, or their total suppression. If we classify the type of the sedimentary structures in the simplest mode of generalization, we arrive at the following series in proceeding from below upward: 1. The so-called 'transition rocks', in the two divisions of upper and lower graywacke (silurian and devonian systems), the latter being formerly designated as old red sandstone. 2. The 'lower trias',* comprising mountain limestone, coal-measures, together with the lower new red sandstone (Todtliegende and Zechstein).** 3. The 'upper trias', including variegated sandstone,** muschelkalk, and keuper. 4. 'Jura limestone' (lias and oolite). 5. 'Green sandstone', the quader sanstein, upper and lower chalk, terminating the secondary formations, which begin with limestone. 6. 'Tertiary formations' in three divisions, distinguished as granular limestone, the lignites, and the sub-Apennine gravel of Italy.

Then follow, in the alluvial beds, the colossal bones of the mammalia of the primitive world, as the mastodon, dinothrium p 278 missurium, and the megatherides, among which is Owen's sloth-like mylodon, eleven feet in the length.*

Besides these extinct families, we find the fossil remains of still extant animals, as the elephant, rhinoceros, ox, horse, and stag. The field near Bogota, called the 'Campo de Gigantes', which is filled with the bones of mastodons, and in which I caused excavations to be made, lies 8740 feet above the level of the sea, while the osseous remains, found in the elevated plateaux of Mexico, belong to true elephants of extinct species.*

The projecting spurs of the Himalaya, the Sewalik Hills, which have been so zealously investigated by Captain Cantley* and Dr. Falconer, and the Cordilleras, whose elevations are probably, of very different epochs, contain, besides numerous mastodons, the sivatherium, and the gigantic land tortoise of the primitive world ('Colossochelys'), which is twelve feet in length and six in height, and several extant families, as elephants, rhinoceroses, and giraffes; and it is a remarkable fact, that these remains are found in a zone which still enjoys the same tropical climate which must be supposed to have prevailed at the period of the mastodons.**

Having thus passed in review both the inorganic formations of the earth's crust and the animal remains which are contained within it, another branch of the history of the organic life still remains for our consideration, viz., the epoch of vegetation, and the successive floras that have occurred simultaneously with the increasing extent of the dry land and the modifications of the atmosphere. The oldest transition strata, as we have already observed, contain merely cellular marine plants, and it is only in the devonian system that a few cryptogamic forms of vascular plants (Calamites and Lycopodiaceae) have been observed.*

Nothing appears to corroborate p 279 the theoretical views that have been started regarding the simplicity of primitive forms of organic life, ow that vegetable preceded animal life, and that the former was necessarily dependent upon the latter. The existence of races of men inhabiting the icy regions of the North Polar lands, and whose nutriment is solely derived from fish and cetaceans, shows the possibility of maintaining life independently of vegetable substances. After the devonian system and the mountain limestone, we come to a formation, the botanical analysis of which has made such brilliant advances in modern times.*

The coal measures contain not only fern-like cryptogamic plants and phanerogamic monocotyledons (grasses, yucc-like Liliaceae and palms), but also gymnospermic dicotyledons (Coniferae and Cycadeae), amounting in all to nearly 400 species, as characteristic of the coal formations. Of these we will only enumerate arborescent Calamites and Lycopodiaceae, scaly Lepidodendra, Sigillariae, which attain a height of sixty feet, and are sometimes found standing upright, being distinguished by a double system of vascular bundles, cactus-like Stigmariae, a great number of ferns, in some cases the stems, and in others the fronds alone being found, indicating by their abundance the insular form of the dry land,* Cycadeae** especially palms, although fewer in number.***

Asterophyllites, having whorl-like leaves, and allied to the Naiades, with araucaria-like Coniferae',* which exhibit faint traces of annual rings.

This difference of character from our present vegtation, minifested in the vegetative forms which were so luxuriously developed on the drier p 280 and more elevated portions of the old red sandstone, was maintained through all the subsequent epochs to the most recent chalk formations; amid the peculiar characteristics exhibited in the vegetable forms contained in the coal measures, there is, however, a strikingly-marked prevalence of the same families, if not of the same species,* in all parts of the earth as it then existed, as in New Holland, Canada, Greenland, and Melville Island.

The vegetation of the primitive period exhibits forms which, from their simultaneous affinity with several families of the present world, testify that many intermediate links must have become extinct in the scale of organic development. Thus, for example, to mention only two instances, we would notice the Lepidodendra, which, according to Lindley, occupy a place between the Coniferae and the Lycopodiaceae*, and the Araucariae and pines, which exhibit some peculiarities in the union of their vascular bundles.

Even if we limit our consideration to the present world alone, we must regard as highly important the discovery of Cycadeae and Coniferae side by side with Sagenariae and Lepidodendra in the ancient coal measures. The Coniferae are not ony allied to Cupuliferae and Betulinae, with which we find them associated in lignite formations, but also with Lycopodiaceae. The family of the sago-like Cycadeae approaches most nearly to palms in its external appearance, while these plants are specially allied to Coniferae in respect to the structure of their blossoms and seed.*

Where many beds of coal are superposed over one another, the families and species are not always blended, being most frequently grouped together in separate genera; Lycopodiaceae and certain ferns being alone found in one bed, and Stigmariae and Sigillariae in another. In order to give some idea of the luxuriance of the vegetation of the primitive world, and of the immense masses of vegetable matter which was doubtlessly accumulated in currents and converted in a moist condition into coal,* I would instance the Saarbrucker coal measures, p 281 where 120 beds are superposed on one another, exclusive of a great many which are less than a foot in thickness; the coal beds at Johnstone, in Scotland, and those in the Creuzot, in Burgundy, are some of them, respectively, thirty and fifty feet in thickness,** while in the forests of our temperate zones, the carbon contained in the trees growing over a certain area would hardly suffice, in the space of a hundred years, to cover it with more than a stratum of seven French lines in thickness.***

Near the mouth of the Mississippi, and in the "wood hills" of the Siberian Polar Sea, described by Admiral Wrangel, the vast number of trunks of trees accumulated by river and sea water currents affords a striking instance of theenormous quantities of drift-wood which must have favored the formation of carboniferous deposition in the island waters and insular bays. There can be no doubt that these beds owe a considerable portion of the substances of which they consist to grasses, small branching shrubs, and cryptogamic plants.

The association of palms and Coniferae, which we have indicated as being characteristic of the coal formations, is discoverable throughout almost all formations to the tertiary period. In the present condition of the world, these genera p 282 appear to exhibit no tendency whatever to occur associated together. We have so accustomed ourselves, although erroneously, to regard Coniferae as a northern form, that I experienced a feeling of surprise when, in ascending from the shores of the South Pacific toward Chilpansingo and the elevated valleys of Mexico, between the 'Venta de la Moxonera' and the 'Alto de los Caxones', 4000 feet above the level of the sea, I rode a whole day through a dense wood of Pinus occidentalis, where I observed that these trees, which are so similar to the Weymouth pine, were associated with fan palms* ('Corypha dulcis'), swarming with brightly-colored parrots.

South America has oaks, but not a single species of pine; and the first time that I again saw the familiar form of a fir-tree, it was thus associated with the strange appearance of the fan palm.*

Christopher Columbus, in his first voyage of discovery, saw Coniferae and palms growing together on the northeastern extremity of the island of Cuba, likewise within the tropics, and scarcely above the level of the sea. This acute observer, whom nothing escaped, mentions the fact in his journal as a remarkable circumstance, and his friend Anghiera, the secretary of Frdinand the Catholic, remarks with astonishment "that 'palmeta' and 'pineta' are found associated together in the newly-discovered land." It is a matter of much importance to geology to compare the present distribution of plants over the earth's surface with that exhibited in the fossil floras of the primitive world. The temperate zone of the southern hemisphere, which is so rich in seas and islands, and where p 283 tropical forms blend so remarkably with those of colder parts of the earth, presents according to Darwin's beautiful and animated descriptions,* the most instructive materials for the study of the present and the past geography of plants.

The history of the primordial ages is, in the strict sense of the word, a part of the history of plants.

Cycadeae, which, from the number of their fossil species, must have occupied a far more important part in the extinct than in the present vegetable world, are associated with the nearly allied Coniferae from the coal formations upward. They are almost wholly absent in the epoch of the variegated sandstone which contains Coniferae of rare and luxuriant structure ('Voltizia, Haidingera, Albertia'); the Cycadeae, however, occur most frequently in the keuper and lias strata, in which more than twenty different forms appear. In the chalk, marine plants and naiades predominate. The forests of Cycadeae of the Jura formations had, therefore, long disappeared, and even in the more ancient tertiary formations they are quite subordinate to the Coniferae and palms.*

The lignites, or beds of brown coal* which are present in all divisions of the tertiary period, present, among the most ancient cryptogamic land plants, some few palms, many Coniferae having distinct annual rings, and foliaceous shrubs of a more or less tropical character.

In the middle tertiary period we again find palms and Cycadeae fully established, and finally a great similarity with our existing flora, manifested in the sudden and abundant occurrence of our pines and firs, Cupuliferae, maples, and poplars. The dicotyledonous stems found in lignite are occasionally distinguished by colossal size and great age. In the trunk of a tree found at Bonn, Noggerath counted 792 annual rings.*

In the north of France, at Yseux, near Abbeville, oaks have been discovered in the turf moors of the Somme which measured fourteen feet in diameter, a thickness which is very remarkable in the Old Continent and without the tropics. According to Goppert's excellent investigations, which, it is hoped, may soon be illustrated by plates, it would appear that "all the amber of the Baltic comes from p 284 a coniferous tree, which, to judge by the still extant remains of wood and the bark at different ages, approaches very nearly to our white and red pines, although forming a distinct species. The amber-tree of the ancient world ('Pinites succifer') abounded in resin to a degree far surpassing that manifested by any extant coniferous tree; for not only were large masses of amber deposited in and upon the bark, but also in the wood itself, following the course of the medullary rays, which, together with ligneous cells, are still discernible under the microscope, and peripherally between the rings, being some times both yellow and white."

"Among the vegetable forms inclosed in amber are male and femald blossoms of our native needle-wood trees and Cupuliferae, while fragments which are recognized as belonging to thuia, cupressus, ephedera, and castania vesca, blended with those of junipers and firs, indicate a vegetation different from that of the coasts and plains of the Baltic."*

We have now passed through the whole series of formations comprised in the geological portion of the present work, proceeding from the oldest erupted rock and the most ancient sedimentary formations to the alluvial land on which are scattered those large masses of rock, the causes of whose general distribution have been so long and variously discussed, and which are, in my opinion, to be ascribed rather to the penetration and violent outpouring of pent-up waters by the elevation of mountain chains than to the motion of floating blocks of ice.*

The most ancient structures of the transition formation p 285 with which we are acquainted are slate and graywacke, which contain some remains of sea weeds from the silurian or cambrian sea. On what did these so-called 'most ancient' formations rest, if gneiss and mica schist must be regarded as changed sedimentary strata? Dare we hazard a conjecture on that which can not be an object of actual geognostic observation? According to an ancient Indian myth, the earth is borne up by an elephant, who in his turn is supported by a gigantic tortoise, in order that he may not fall; but it is not permitted to the credulous Brahmins to inquire on what the tortoise rests. We venture here upon a somewhat similar problem, and are prepared to meet with opposition in our endeavors to arrive at its soluion. In the first formation of the planets, as we stated in the astronomical portion of this work, it is probable that nebulous rings revolving round the sun were agglomerated into spheroids, and consolidated by a gradual condensation proceeding from the exterior toward the center. What we term the ancient silurian strata are thus only the upper portions of the solid crust of the earth. The erupted rocks which have broken through and upheaved these strata have been elevated from depths that are wholly inaccessible to our research; they must, therefore, have existed under the silurian strata, and been composed of the same association of minerals which we term granite, augite, and quartzose porphyry, when they are made known to us by eruption through the surface. Basing our inquiries on analogy, we may assume that the substances which fill up deep fissures and traverse the sedimentary strata are merely the ramifications of a lower deposit. The foci of active volcanoes are situated at enormous depths, and judging from the remarkable fragments which I have found in various parts of the earth incrusted in lava currents, I should deem it more than probable tht a primordial granite rock forms the substratum of the whole stratified edifice of fossil remains.*

Basalt containing olivine first shows itself in the period of the chalk trachyte still later, while eruptions of granite belong, as we learn from the products of their metamorphic action to the epoch of the oldest sedimentary strata of the transition formation. Where knowledge can not be attained from immediate perceptive evidence, we may be allowed from induction, no less than from a careful comparison of facts, to hazard a conjecture by which granite would be restored p 286 to a portion of its contested right and title to be considered as a 'primordial' rock.

The recent progress of geognosy, that is to say, the more extended knowledge of the geognostic epochs characterized by differences of mineral formations, by the peculiarities and succession of the organisms contained within them, and by the position of the strata, whether uplifted or inclined horizontally, leads us, by means of the causal connection existing among all natural phenomena, to the distribution of solids and fluids into the continents and seas which constitute the upper crust of our planet. We here touch upon a point of contact between geological and geographical geognosy which would constitute the complete history of the form and extent of continents. The limitation of the solid by the fluid parts of the earth's surface and their mutual relations of area, have varied very considerably in the long series of geognostic epochs. They were very different, for instance, when carboniferous strata were horizontally deposited on the inclined beds of the mountain limestone and old red sandstone; when lias and oolite lay on a substratum of keuper and muschelkalk, and the chalk rested on the slopes of green sandstone and Jura limestone. If, with Elie de Beaumont, we term the waters in which the Jura limestone and chalk formed a soft deposit the 'Jurassic or oolitic', and the 'cretaceous seas', the outlines of these formations will indicate, for the two corresponding epochs, the boundaries between the already dried land and the ocean in which these rocks were forming. An ingenious attempt has been made to craw maps of this physical portion of primitive geography and we may consider such diagrams as more correct than those of the wanderings of Io or the Homeric geography, since the latter are merely graphic representations of mythical images, while the former are based upon positive facts deduced from the science of geology.

The results of the investigations made regarding the areal relations of the solid portions of our planet are as follows: in the most ancient times, during the silurian and devonian transition epochs, and in the secondary formations, including the trias, the continental portions of the earth were limited to insular groups covered with vegetation; these islands at a subsequent period became united, giving rise to numerous lakes and deeply-indented bays; and finally, when the chains of the Pyrenees, Apennines, and Carpathian Mountains were elevated about the period of the more ancient tertiary formations, large continents appeared, having almost their present p 287 size.*

In the silurian epoch, as well as in that in which the Cycadeae flourished in such abundance, and gigantic saurians were living, the dry land, from pole to pole, was probably less than it now is in the South Pacific and the Indian Ocean. We shall see, in a subsequent part of this work, how this preponderating quantity of water, combined with other causes, must have contributed to raise the temperature and induce a greater uniformity of climate. Here we would only remark in considering the gradual extension of the dry land, that, shortly before the 'disturbances' which at longer or shorter intervals caused the sudden destruction of so great a number of colossal vertebrata in the 'diluvial period', some parts of the present continental masses must have been completely separated from one another. There is a great similarity in South America and Australia between still living and extinct species of animals. In New Holland, fossil remains of the kangaroo have been found, and in New Zealand the semi-foxxilized bones of an enormous bird, resembling the ostrich, the dinornis of Owen,* which is nearly allied to the present spteryx, and but little so to the recently extinct dronte (dodo) of the island of Rodriguez.

The form of the continental portions of the earth may, perhaps, in a great measure, owe their elevation above the surrounding level of the water to the eruption of quartzose porphyry, which overthrew with violence the first great vegetation from which the matrial of our present coal measures was formed. The portions of the earth's surface which we term plains are nothing more than the broad summits of hills and mountains whose bases rest on the bottom of the ocean. Every plain is, therefore, when considered according to its submarine relations, an 'elevated plateau', whose inequalities have been covered over by horizontal deposition of new sedimentary formations and by the accumulation of alluvium.

p 288 Among the general subjects of contemplation appertaining to a work of this nature, a prominent place must be given, first, in the consideration of the 'quantity' of the land raised above the level of the sea, and next, to the individual configuration of each part, either in relation to horizontal extension (relations of form) or to vertical elevation (hypsometrical relations of mountain-chains). Our planet has two envelopes, of which one, which is general -- the atmosphere -- is composed of an elastic fluid, and the other -- the sea -- is only locally distributed, surrounding, and therefore modifying, the form of the land. These two envelopes of air and sea constitute a natural whole, on which depend the difference of climate on the earth's surface, according to the relative extension of the aqueous and solid parts, the form and aspect of the land, and the direction and elevation of mountain chains. A knowledge of the reciprocal action of air, sea, and land teaches us that great meteorological phenomena can not be comprehended when considered independently of geognostic relations. Meteorology, as well as the geography of plants and animals, has only begun to make actual progress since the mutual dependence of the phenomena to be investigated has been fully recognized. The word climate has certainly special reference to the character of the atmosphere, but this character is itself dependent on the perpetually concurrent influences of the ocean, which is universally and deeply agitated by currents having a totally opposite temperature, and of radiation from the dry land, which varies greatly in form, elevation, color, and fertility, whether we consider its bare, rocky portions, or those that are covered with arborescent or herbaceous vegetation.

In the present condition of the surface of our planet, the area of the solid is to that of the fluid parts as 1:2 4/5ths (according to Rigaud, as 100:270).*

The islands form scarcely 1/22d of the continental masses, which are so unequally divided that they consist of three times more land in the northern than in the southern hemisphere; the latter being, therefore, pre-eminently oceanic. From 40 degrees south latitude to the Antarctic pole the earth is almost entirely covered with water. The fluid element predominates in like manner between the eastern shores of the Old and the western shores of the New Continent, being only interspersed with some few insular groups. The learned hydrographer Fleurieu has very justly named this p 289 vast oceanic basis, which, under the tropics, extends over 145ºdegrees of longitude, the 'Great Ocean', in contradistinction to all other seas. The southern and western hemispheres (reckoning the latter from the meridian of Teneriffe) are therefore more rich in water than in any other region of the whole earth.

These are the main points involved in the consideration of the relative quantity of land and sea, a relation which exercises so important an influence on the distribution of temperature, the variations in atmospheric pressure, the direction of the winds, and the quantity of moisture contained in the air, with which the development of vegetation is so essentially connected. When we consider that nearly three fourths of the upper surface of our planet are covered with water,* we shall be less surprised at the imperfect condition of meteorology before the beginning of the present century, since it is only during the subsequent period that numerous accurate observations on the temperature of the sea at different latitudes and at different seasons have been made and numerically compared together.

The horizontal configuration of continents in their general relations of extension was already made a subject of intellectual contemplation by the ancient Greeks. Conjectures were advanced regarding the maximum of the extension from west to east, and Dicaearchus placed it, according to the testimony of Agathemerus, in the latitude of Rhodes, in the direction of a line passing from the Pillars of Hercules to Thine. This line, which has been termed 'the parallel of the diaphragm of Dicaearchus', is laid down with an astronomical accuracy of position, which, as I have stated in another work, is well worthy of exciting surprise and admiration.*

Strabo, who was probably influenced by Eratosthenes, appears to have been so firmly convinced that this parallel of 36 degrees was the maximum of the extension of the then existing world, that he supposed it had some intimate connection with the form of the earth, and therefore places under this line the continent whose existence p 290 he divined in the northern hemisphere, between Theria and the coasts of Thine.*

As we have already remarked, one hemisphere of the earth (whether we divide the sphere through the equator or through the meridian of Teneriffe) has a much greater expansion of elevated land than the opposite one: these two vast ocean-girt tracts of land, which we term the eastern and western, or the Old and New Continents, present, however, conjointly with the most striking contrasts of configuration and position of their axes, some similarities of form, especially with reference to the mutual relations of their opposite coasts. In the eastern continent, the predominating direction -- the position of the major axis -- inclines from east to west (or, more correctly speaking, from southwest to northeast), while in the western continent it inclines from south to north (or, rather, from south-southeast to north-northwest). Both terminate to the north at a parallel coinciding nearly with that of 70ºdegrees, while they extend to the south in pyramidal points, having submarine prolongations of islands and shoals. Such, for instance, are the Archipelago of Tierra del Fuego, the Lagullas Bank south of the Cape of Good Hope, and Van Diemen's Land, separated from New Holland by Bass's Straits. Northern Asia extends to the above parallel at Cape Taimura, which, according to Krusenstern, is 78 degrees 16', while it falls below it from the mouth of the Great Tschukotsehja River eastward to Behring's Straits, in the eastern extremity of Asia -- Cook's East Cape -- which, according to Beechey, is only 66 degrees E.*

The northern shore of the New Continent follows with tolerable exactness the parallel of 70 degrees, since the lands to the north and south of Barrow's Strait, from Boothia Felix and Victoria Land, are merely detached islands.

The pyramidal configuration of all the southern extremities of continents belongs to the 'similtudines physicae in configuratione mundi', to which Bacon already called attention in his 'Novum Organon', and with which Reinhold Foster, one of Cook's companions in his second voyage of circumnavigation, connected some ingenious considerations. On looking eastward from the meridian of Teneriffe, we perceive that the southern extremities of the three continents, viz., Africa as the extreme p 291 of the Old World, Australia, and South America, successively approach nearer toward the south pole. New Zealand, whose length extends fully 12 degrees of latitude, forms an intermediate link between Australia and South America, likewise terminating in an island, New Leinster. It is also a remarkable circumstance that the greatest extension toward the south falls in the Old Continent, under the same meridian in which the extremest projection toward the north pole is manifested. This will be perceived on comparing the Cape of Good Hope and the Lagullas Bank with the North Cape of Europe, and the peninsula of Malacca with Cape Taimura in Siberia.*

We know not whether the poles of the earth are surrounded by land or by a sea of ice. Toward the north pole the parallel of 82 degrees 55' has been reached, but toward the south pole only that of 78 degrees 10'.

The pyramidal terminations of the great continents are variously repeated on a smaller scale, not only in the Indian Ocean and in the peninsulas of Arabia, Hindostan, and Malacca, but also, as was remarked by Eratosthenes and Polybius, in the Mediterranean, where these writers had ingeniously compared together the forms of the Iberian, Italian, and Hellenic peninsulas.*

Europe, whose area is five times smaller than that of Asia, may almost be regarded as a multifariously articulated western peninsula of the more compact mass of the ontinent of Asia, the climatic relations of the former being to those of the latter as the peninsula of Brittany is to the rest of France.

The influence exercised by the articulation and higher development of the form of a continent on the moral and intellectual condition of nations was remarked by Strabo,* who extols p 292 the varied form of our small continent as a special advantage.

Africa* and South America, which manifest so great a resemblence in their configuration, are also the two continents that exhibit the simplest littoral outlines.

It is only the eastern shores of Asia, which, broken as it were by the force of the currents of the ocean* ('fractas ex aequore terra'), exhibit a richly-variegated configuration, peninsulas and contiguous islands alternating from the equator to 60 degrees north latitude.

Our Atlantic Ocean presents all the indications of a valley. It is as if a flow of eddying waters had been directed first toward the northeast, then toward the northwest, and back again to the northeast. The parallelism of the coasts north of 10 degrees south latitude, the projecting and receding angles, the convexity of Brazil opposite to the Gulf of Guinea, that of Africa under the same parallel, with the Gulf of the Antilles, all favor this apparently speculative view.*

In this Atlantic valley, as is almost every where the case in the configuration of large continental masses, coasts deeply indented, and rich in islands, are situated opposite to those possessing a different character. I long since drew attention to the geognostic importance of entering into a comparison of the western coast of Africa and of South America within the tropics. The deeply curved indentation of the African continent at Fernando Po, 4 degrees 30' north latitude, is repeated on the coast of the Pacific at 18 degrees 15' south latitude, between the Valley of Arica and the Morro de Juan Diaz, where the Peruvian coast suddenly changes the direction from wouth to north which it had previously followed, and inclines to the northwest. This change p 293 of direction extends in like manner to the chain of the Andes, which is divided into two parallel branches affecting not only the littoral portions,* but even the eastern Cordilleras.

In the latter, civilization had its earliest seat in the South American plateaux where the small Alpine lake of Titicaca bathes the feet of the colossal mountains of Sorata and Illimani. Further to the south, from Valdiva and Chiloë (40 degrees to 42 degrees south latitude), through the Archipelago 'de los Chonos' to 'Terra del Fuego', we find repeated that singular configuration of 'fiords' (a blending of narrow and deeply-indented bays), which in the Northern hemisphere characterizes the western shores of Norway and Scotland.

These are the most general considerations suggested by the study of the upper surface of our planet with reference to the form of continents, and their expansion in a horizontal direction. We have collected facts and brought forward some analogies of configuration in distant parts of the earth, but we do not venture to regard them as fixed laws of form. When the traveler on the declivity of an active volcano, as, for instance, of Vesuvius, examines the frequent partial elevations by which portions of the soil are often permanently upheaved several feet above their former level, either immediately precediing or during the continuance of an eruption, thus forming roof-like or flattened summits, he is taught how accidental conditions in the expression of the force of subterranean vapors, and in the resistance to be overcome, may modify the feeble perturbations in the equilibrium of the internal elastic forces of our planet may have inclined them more to its norther than to its southern direction, and caused the continent in the eastern part of the globe to present a broad mass, whose major axis is almost parallel with the equator, while in the western and more oceanic part the southern extremity is extremely narrow.

Very little can be empirically determined regarding the causal connection of the phenomena of the formation of continents, or of the analogies and contrasts presented by their p 294 configuration. All that we know regarding this subject resolves itself into this one point, that the active cause is subterranean; that continents did not arise at once in the form they now present, but were, as we have already observed, increased by degrees by means of numerous oscillatory elevations and depressions of the soil, or were formed by the fusion of separate smaller continental masses. Their present form is, therefore, the result of two causes, which have exercised a consecutive action the one on the other; the first is the expression of subterranean force, whose direction we term accidental, owing to our inability to defint it, from its removal from within the sphere of our comprehension, while the second is derived from forces acting on the surface, among which volcanic eruptions, the elevation of mountains, and currents of sea water play the principal parts. How totally different would be the condition of the temperature of the earth, and consequently, of the state of vegetation, husbandry, and human society, if the major axis of the New Continent had the same direction as that of the Old Continent; if, for instance, the Cordilleras, instead of having a southern direction, inclined from east to west; if there had been no radiating tropical continent, like Africa, to the south of Europe; and if the Mediterranean, which was once connected with the Caspian and Red Seas, and which has become so powerful a means of furthering the intercommunication of nations, had never existed, or if it had been elevated like the plains of Lombardy and Cyrene?

The changes of the reciprocal relations of height between the fluid and solid portions of the earth's surface (changes which, at the same time, determine the outlines of continents, and the greater or lesser submersion of low lands) are to be ascribed to numerous unequally working causes. The most powerful have incontestably been the force of elastic vapors inclosed in the interior of the earth, the sudden change of temperature of certain dense strata,* the unequal secular loss of p 295 heat experienced by the crust and nucleus of the earth, occasioning ridges in the solid surface, local modifications of gravitation,** and, as a consequence of these alterations, in the curvature of a portion of the liquid element.

According to the views generally adopted by geognosists in the present day and which are supported by the observation of a series of well-attested facts, no less than by analogy with the most important volcanic phenomena, it would appear that the elevation of continents is actual, and not merely apparent or owing to the configuration of the upper surface of the sea. The merit of having advanced this view beloongs to Leopold von Buch, the narrative of his memorable 'Travels through Norway and Sweden' in 1806 and 1807.*

While the whole coast of Sweden and Finland, from Solvitzborg, on the limits of Northern Scania, past Gefle to Tornea, and from Tornea to Abo, experiences a gradual rise of four feet in a century, the southern part of Sweden is, according to Neilson, undergoing a simultaneous depression.*

The maximum of this elevating p 296 force appears to be in the north of Lapland, and to diminish gradually to the south toward Calmar and Solvitzborg. Lines marking the ancient level of the sea in pre-historic times are indicated throughout the whole of Norway,* from Cape Lindesnaes to the extremity of the North Cape, by banks of shells identical with those of the present seas, and which have lately been most accurately examined by Bravais during his long winter sojourn at Bosekop.

These banks lie nearly 650 feet above the present mean level of the sea, and reappear, according to Keilhau and Eugene Robert, in a north-northwest direction on the coasts of Spitzbergen, opposite the North Cape. Leopold von Buch, who was the first to draw attention to the high banks of shells at Tromsoe (latitude 69 degrees 40'), has, however, shown that the more ancient elevations on the North Sea appertain to a different class of phenomena, from the regular and gradual retrogressive elevations of the Swedish shores in the Gulf of Bothnia. This latter phenomenon, which is well attested by historical evidence, must not be confounded with the changes in the level of the soil occasioned by earthquakes, as on the shores of Chili and of Cutch, and which have recently given occasion to similar observations in other countries. It has been found that a perceptible sinking resulting from a disturbance of the strata of the upper surface sometimes occurs, corresponding with an elevation elsewhere, as, for instance, in West Greenland, according to Pingel and Graah, in Dalmatia and in Scania.

Since it is highly probable that the oscillatory movements of the soil, and the rising and sinking of the upper surface, were more strongly marked in the early periods of our planet than at present, we shall be less surprised to find in the interior of continents some few portions of the earth's surface lying below the general level of existing seas. Instances of this kind occur in the soda lakes described by General Andreossy, the small bitter lakes in the narrow Isthmus of Suez, the Caspian Sea, the Sea of Tiberias, and especially the Dead Sea.*

The level of the water in the two last-named seas is p 297 666 and 1312 feet below the level of the Mediterranean. If we could suddenly remove the alluvial soil which covers the rocky strata in many parts of the earth's surface, we should discover how great a portion of the rocky crust of the earth was then below the present level of the sea. The periodic, although irregularly alternating rise and fall of the water of the Caspian Sea, of which I have myself observed evident traces in the northern portions of its basin, appears to prove,* as do also the observations of Darwin on the coral seas,** that without earthquakes, properly so- called, the surface of the earth is capable of the same gentle and progressive oscillations as those which must have prevailed so generally in the earliest ages, when the surface of the hardening crust of the earth was less compact than at present.

The phenomena to which we would here direct attention remind us of the instability of the present order of things, and of the changes to which the outlines and configuration of continents are probably still subject at long intervals of time. That which may scarcely be perceptible in one generation, accumulates during periods of time, whose duration is revealed to us by the movement of remote heavenly bodies. The eastern coast of the Scandinavian peninsula has probably risen p 298 about 320 feet in the space of 8000 years; and in 12,000 years, if the movement be regular, parts of the bottom of the sea which lie nearest the shores, and are in the present day covered by nearly fifty fathoms of water, will come to the surface and constitute dry land. But what are such intervals of time compared to the length of the geognostic periods revealed to us in the stratified series of formations, and in the world of extinct and varying organisms! We have hitherto only considered the phenomena of elevation; but the analogies of observed facts lead us with equal justice to assume the possibility of the depression of whole tracts of land. The mean elevation of the non-mountainous parts of France amounts to less than 480 feet. It would not, therefore, require any long period of time, compared with the old geognostic periods, in which such great changes were brought about in the interior of the earth, to effect the permanent submersion of the northwestern part of Europe, and induce essential alterations in its littoral relations.

The depression and elevation of the solid or fluid parts of the earth -- phenomena which are so opposite in their action that the effect of elevation in one part is to produce an apparent depression in another -- are the causes of all the changes which occur in the configuration of continents. In a work of this general character, and in an impartial exposition of the phenomena of nature, we must not overlook the 'possibility' of a diminution of the quantity of water, and a constant depression of the level of seas. Thgere can scarcely be a doubt that, at the period when the temperature of the surface of the earth was higher, when the waters were inclosed in larger and deeper fissures, and when the atmosphere possessed a totally different character from what it does at present, great changes must have occurred in the level of seas, depending upon the increase and decrease of the liquid parts of the earth's surface. But in the actual condition of our planet, there is no direct evidence of a real continuous increase or decrease of the sea, and we have no proof of any gradual change in its level at certain definite points of observation, as indicated by the mean range of the barometer. According to experiments made by Daussy and Antonio Nobile, an increase in the height of the barometer would in itself be attended by a depression in the level of the sea. But as the mean pressure of the atmosphere at the level of the sea is not the same at all latitudes, owing to meteorological causes depending upon the direction of the wind and varying degrees of moisture, the p 299 barometer alone can not afford a certain evidence of the general change of level in the ocean. The remarkable fact that some of the ports in the Mediterranean were repeatedly left dry during several hours at the beginning of this century, appears to show that currents may by changes occurring in their direction and force, occasion a 'local'' retreat of the sea, and a permanent drying of a small portion of the shore, without being followed by any actual diminution of water, or any permanent depression of the ocean. We must, however, be very cautious in applying the knowledge which we have lately arrived at, regarding these involved phenomena, since we might otherwise be led to ascribe to water as the elder element, what ought to be referred to the two other elements, earth and air.

As the 'external' configuration of continents, which we have already described in their horizontal expansion, exercises, by their variously indented littoral outlines, a favorable influence on climate, trade, and the progress of civilization, so likewise does their internal articulation, or the vertical elevation of the soil (chains of mountains and elevated plateaux), give rise to equally important results. Whatever produces a polymorphic diversity of forms on the surface of our planetary habitation -- such as mountains, lakes, grassy savannas, or even deserts encircled by a band of forests -- impresses some peculiar character on the social condition of the inhabitants. Ridges of high land covered by snow impede intercourse; but a blending of low, discontinued mountain chains* and tracts of valleys, as we see so happily presented in the west and south of Europe, tends to the multiplication of meteorological processes and the products of vegetation, and, from the variety manifested in different kinds of cultivation in each district, even under the same degree of latitude, gives rise to wants that stimulate the activity of the inhabitants.

Thus the awful revolutions, during which, by the action of the interior on the crust of the earth, great mountain chains have been elevated by the sudden upheaval of a portion of the oxydized exterior of our planet, have served, after the establishment of repose, and on the revival of organic life, to furnish a richer and more beautiful variety of individual forms, and in a great measure to remove from the earth that aspect of dreary p 300 uniformity which exercises so impoverishing an influence on the physical and intellectual powers of mankind.

According to the grand views of Elie de Beaumont, we must ascribe a relative age to each system of mountain chains* on the supposition that their elevation must necessarily have occurred between the period of the deposition of the vertically elevated strata and that of the horizontally inclined strata running at the base of the mountains.

The ridges of the Earth's crust -- elevations of strata which are of the same geognostic age -- appear, moreover, to follow one common direction. The line of strike of the horizontal strata is not always parallel with the axis of the chain, but intersects it, so that, according to my views,* the phenomenon of elevation of the strata, which is even found to be repeated in the neighboring plains, must be more ancient than the elevation of the chain.

The main direction of the whole continent of Europe (from southwest to northeast) is opposite to that of the great fissures which pass from northwest to southeast, from the mouths of the Rhine and Elbe, through the Adriatic and Red Seas, and through the mountain system of Putschi-Koh in Luristan, toward the Persian Gulf and the Indian Ocean. This almost rectangular intersection of geodesic lines exercises an important influence on the commercial relations of Europe, Asia, and the northwest of Africa, and on the progress of civilization on the formerly more flourishing shores of the Mediterranean.*

Since grand and lofty mountain chains so strongly excite our imagination by the evidence they afford of great terrestrial revolutions, and when considered as the boundaries of climates, as lines of separation for waters, or as the site of a different form of vegetation, it is the more necessary to demonstrate, by a correct numerical estimation of their volume, how small is the quantity of their elevated mass when compared with the area of the adjacent continnents. The mass of the Pyrenees, for instance, the mean elevation of whose summits, and the real quantity of whose base have been ascertained by accurate measurements, would if scattered over p 301 the surface of France, only raise its mean level about 115 feet. The mass of the eastern and western Alps would in like manner only increase the height of Europe about 21 1/2 feet above its present level. I have found by a laborious investigation,* which from its nature, can only give a maximum limit, that the center of gravity of the volume of the land raised above the present level of the sea in Europe and North America is respectively situated at an elevation of 671 and 748 feet, while it is at 1132 and 1152 feet in Asia and South America.

These numbers show the low level of norther regions. In Asia the vast steppes of Siberia are compensated for by the great elevations of the land (between the Himalaya, the North Thibetian chain of Kuen-lun, and the Celestial Mountains), from 28 degrees 30' to 40 degrees north latitude. We may, to a certain extent, trace in these numbers the portions of the Earth in which the Plutonic forces were most intensely manifested in the interior by the upheaval of continental masses.

There are no reasons why these Plutonic forces may not, in future ages, add new mountain systems to those which Elie de Beaumont has shown to be of such different ages, and inclined in such different directions. Why should the crust of the Earth have lost its property of being elevated in the ridges? The recently-elevated mountain systems of the Alps and the Cordilleras exhibit in Mont Blanc and Monte Rosa, in Sorata, Illimani, and Chimborazo, colossal elevations which do not favor the assumption of a decrease in the intensity of the subterranean forces. All geognostic phenomena indicate the periodic alternation of activity and repose;* but the quiet we now enjoy is only apparent.

The tremblings which still agitate the surface under all latitudes, and in every species of rock, the elevation of Sweden, the appearance of new islands of eruption, are all conclusive as to the unquiet condition of our planet.

p 302 The two envelopes of the solid surface of our planet -- the liquid and the aeriform -- exhibit, owing to the mobility of their particles, their currents, and their atmospheric relations, many analogies combined with the contrasts which arise from the great difference in the condition of their aggregation and elasticity. The depths of ocean and of air are alike unknown to us. At some few places under the tropics no bottom has been found with soundings of 276,000 (or more than four miles), while in the air, if, according to Wollaston, we may assume that it has a limit from which waves of sound may be reverberated, the phenomenon of twilight would incline us to assume a height at least nine times as great.*

The aërial ocean rests partly on the solid earth, whose mountain chains and elevated plateaux rise, as we have already seen, like green wooded shoals, and partly on the sea, whose surface forms a moving base, on which rest the lower, denser, and more saturated strata of air.

Proceeding upward and downward from the common limit of the aërial and liquid oceans, we find that the strata of air and water are subject to determinate laws of decrease of temperature. This decrease is much less rapid in the air than in the sea, which has a tendency under all latitudes to maintain its temperature in the strata of water most contiguous to the atmosphere, owing to the sinking of the heavier and more cooled particles. A large series of the most carefully conducted observations on temperature shows us that in the ordinary and mean condition of its surface, the ocean from the equator to the forty-eighth degree of north and south latitude is somewhat warmer than the adjacent strata of air.*

Owing to this decrease of temperature at increasing depths, fishes and other inhabitants of the sea, the nature of whose digestive and respiratory organs fits them for living in deep water, may even, under the tropics, find the low degree of temperature and the coolness of climate characteristic of more temperate and more northern latitudes. This circumstance, which is analogous to the prevalence of a mild and even cold air on the elevated plains of the torrid zone, exercises a special influence on the migration and geographical distribution of many marine animals. Moreover, the depths at which fishes live, modify, by the increase of pressure, their cutaneous respiration, and the p 303 oxygenous and nitrogenous contents of the swimming bladders.

As fresh and salt water do not attain the maximum of their density at the same degree of temperature, and as the saltness of the sea lowers the thermometrical degree corresponding to this point, we can understand how the water drawn from breat depths of the sea during the voyages of the Kotzebue and Dupetit-Thouars could have been found to have only the temperature of 37 degrees and 36.5 degrees. This icy temperatureof sea water, which is likewise manifested at the depths of tropical seas, first led to a study of the lower polar currents, which move from both poles toward the equator. Without these submarine currents, the tropical seas at those depths could only have a temperature equal to the local maximum of cold possessed by the falling particles of water at the radiating and cooled surface of the tropical sea. In the Mediterranean, the cause of the absence of such a refrigeration of the lower strata is ingeniously explained by Arago, on the assumption that the entrance of the deeper polar currents into the Straits of Gibraltar, where the water at the surface flows in from the Atlantic Ocean from west to east, is hindered by the submariine counter-currents which move from east to west, from the Mediterranean into the Atlantic.

The ocean, which acts as a general equalizer and moderator of climates, exhibits a most remarkable uniformity and constancy of temperature, especially between 10 degrees north and 10 degrees south latitude,* over spaces of many thousands of square miles, at a distance from land where it is not penetrated by currents of cold and heated water.

It has therefore, been justly observed, that an exact and long-continued investigation of these thermic relations of the tropical seas might most easily afford a solution to the great and much-contested problem of the permanence of climates and terrestrial temperatures.*

Great changes in the luminous disk of the sun would, p 304 if they were of long duration, be reflected with more certainty in the mean temperature of the sea than in that of the solid land.

The zones at which occur the maxima of the oceanic temperature and of the density (the saline contents) of its waters, do not correspond with the equator. The two maxima are separated from one another, and the waters of the highest temperature appear to form two nearly parallel lines north and south of the geographical equator. Lenz, in his voyage of circumnavigation, found in the Pacific the maxima of density in 22 degrees north and 17 degrees south latitude, while its minimum was situated a few degrees to the south of the equator. In the region of calms the solar heat can exercise but little influence on evaporation, because the stratum of air impregnated with saline aqueous vapor, which rests on the surface of the sea, remains still and unchanged.

The surface of all connected seas must be considered as having a general perfectly equal level with respect to their mean elevation. Local causes (probably prevailing winds and currents) may, however, produce permanent, although trifling changes in the level of some deeply indented bays, as for instance, the Red Sea. The highest level of the water at the Isthmus of Suez is at different hours of the day from 24 to 30 feet above that of the Mediterranean. The form of the Straits of Bab-el-Mandeb, through which the waters appear to find an easier ingress than egress, seems to contribute to this remarkable phenomenon, which was known to the ancients.*

The admirable geodetic operations of Coraboeuf and Delcrois show that no perceptible difference of level exists between the upper surfaces of the Atlantic and the Mediterranean, along the chain of the Pyrenees, or between the coasts of northern Holland and Marseilles.*

p 305 Disturbances of equilibrium and consequent movements of the waters are partly irregular and transitory, dependent upon winds, and producing waves which sometimes, at a distance from the shore and during a storm, rise to a height of more than 35 feet; partly regular and periodic, occasioned by the position and attraction of the sun and moon, as the ebb and flow of the tides; and partly permanent, although less intense, occurring as oceanic currents. The phenomena of tides, which prevail in all seas (with the exception of the smaller ones that are completely closed in, and where the ebbing and flowing waves are scarcely or not at all perceptible), have been perfectly explained by the Newtonian doctrine, and thus brought "within the domain of necessary facts." Each of these periodically-recurring oscillations of the waters of the sea has a duration of somewhat more than half a day. Although in the open sea they scarcely attain an elevation of a few feet, they often rise considerably higher where the waves are opposed by the configuration of the shores, as for instance, at St. Malo and in Nova Scotia, where they reach the respective elevation of 50 feet, and of 65 to 70 feet. "It has been shown by the analysis of the great geometrician Laplace, that, supposing the depth to be wholly inconsiderable when compared with the radius of the earth, the stability of the equilibrium of the sea requires that the density of its fluid should be less than that of the earth; and, as we have already seen, the earth's density is in fact five times greater than that of water. The elevated parts of the land can not therefore be overflowed, nor can the remains of marine animals found on the summits of mountains have been conveyed to those localities by any previous high tides.*

It is no slight

This material taken from pages 305-362

COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt

Translated by E C Otte

from the 1858 Harper & Brothers edition of Cosmos, volume 1 --------------------------------------------------

p 305 [balance of p 305 is in file "09 Humboldt"] It is no slight p 306 evidence of the importance of analysis, which is too often regarded with contempt among the unscientific, that Laplace's perfect theory of tides has enabled us, in our astronomical ephemerides, to predict the height of spring-tides at the periods of new and full moon, and thus put the inhabitants of the sea-shore on their guard against the increased danger attending these lunar revolutions.

Oceanic currents, which exercise so important an influence on the intercourse of nations and on the climatic relations of adjacent coasts, depend conjointly upon various causes, differing alike in nature and importance. Among these we may reckon the periods at which tides occur in their progress round the earth; the duration and intensity of prevailing winds; the modifications of density and specific gravity which the particles of water undergo in consequence of differences in the temperature and in the relative quantity of saline contents at different latitudes and depths;* and, lastly, the horary variations of the atmospheric pressure, successively propagated from east to west, and occurring with such regularity in the tropics.

These currents present a remarkable spectacle; like rivers of uniform breadth, they cross the sea in different directions, while the adjacent strata of water, which remain undisturbed, form, as it were, the banks of these moving streams. This diffrence between the moving waters and those at rest is most strikingly manifested where long lines of sea-weed, borne onward by the current, enable us to estimate its velocity. In the lower strata of the atmosphere, we may sometimes, during a storm, observe similar phenomena in the limited aerial current, which is indicated by a narrow line of trees, which are often found to be overthrown in the midst of a dense wood.

The general movement of the sea from east to west between p 307 the tropics (termed the equatorial or rotation currnt) is considered to be owing to the propagation of tides and to the trade winds. Its direction is changed by the resistance it experiences from the prominent eastern shores of continents. The results recently obtained by Daussy regarding the velocity of this current, estimated from observations made on the distances traversed by bottles that had purposely been thrown into the sea, agree within one eighteenth with the velocity of motion (10 French nautical miles, 952 toises each, in 24 hours) which I had found from a comparison with earlier experiments.*

Christopher Columbus, during his third voyage, when he was seeking to enter the tropics in the meridian of Teneriffe, wrote in his journal as follows:* "I regard it as proved that the waters of the sea move from east to west, as do the heavens ('las aguas van con los cielos'), that is to say, like the apparent motion of the sun, moon, and stars."

The narrow currents, or true oceanic rivers which traverse the sea, bring warm water into higher and cold water into lower latitudes. To the first class belongs the celebrated Gulf Stream,* which was known to Anghiera, and more especially to Sir Humphrey Gilbert in the sixteenth century.

Its first impulse and origin is to be sought to the south of the Cape of Good Hope; after a long circuit it pours itself from the Caribbean Sea and the Mexican Gulf through the Straits of the Bahamas, and, following a course from south-southwest to north-northeast, continues to recede from the shores of the United States, until, further deflected to the eastward by the Banks of Newfoundland, it approaches the European coasts, frequently throwing a quantity of tropical seeds ('Mimosa scandens, Guilandina bonduc, Dolichos urens') on the shores of Ireland, the Hebrides, and Norway. The northeastern prolongation tends to mitigate the cold of the ocean, and to ameliorate the climate on the most northern extremity of Scandinavia. At the point where the Gulf Stream p 308 is deflected from the Banks of Newfoundland toward the east, it sends off branches to the south near the Azores.*

This is the situation of the Sargasso Sea, or that great bank of weeds which so vividly occupied the imagination of Christopher Columbus, and which Oviedo calls the sea-weed meadows ('Praderias de yerva'). A host of small marine animals inhabits these tently-moved and evergreen masses of 'Fucus natans', one of the most generally distributed of the social plants of the sea.

The counterpart of this current (which in the Atlantic Ocean, between Africa, America, and Europe, belongs almost exclusively to the northern hemisphere) is to be found in the South Pacific, where a current prevails, the effect of whose low temperature on the climate of the adjacent shores I had an opportunity of observing in the autumn of 1802. It brings the cold waters of the high southern latitudes to the coast of Chili, follows the shores of this continent and of Peru, first from south to north, and is then deflected from the Bay of Arica onward from south-southeast to north-northwest. At certain seasons of the year the temperature of this cold oceanic current is, in the tropics, only 60 degrees, while the undisturbed adjacent water exhibits a temperature of 81.5 degrees and 83.7 degrees. On that part of the shore of South America south of Payta, which inclines furthest westward, the current is suddenly deflected in the same direction from the shore, turning so sharply to the west that a ship sailing northward passes suddenly from cold into warm water.

It is not known to what depth cold and warm oceanic currents propagate their motion; but the deflection experienced by the South African current, from the Lagullas Bank, which is fully from 70 to 80 fathoms deep, would seem to imply the existence of a far-extending propagation. Sand banks and shoals lying beyond the line of these currents may, as was first discovered by the admirable Benjamin Franklin, be recognized by the coldness of the water over them. This depression of the temperature appears to me to depend upon the fact that, by the propagation of the motion of the sea, deep waters rise to the margin of the banks and mix with the upper strata. My lamented friend, Sir Humphrey Davy, ascribed this phenomenon (the knowledge of which is often of great practical utility in securing the safety of the navigator) to the descent of the particles of water that had been cooled by nocturnal radiation p 309 and which remain nearer to the surface, owing to the hinderance placed in the way of their greater descent by the intervention of sand-banks. By his observations Franklin may be said to have converted the thermometer into a sounding line. Mists are frequently found to rest over these depths, owing to the condensation of the vapor of the atmosphere by the cooled waters. I have seen such mists in the south of Jamaica, and also in the Pacific, defining with sharpness and clearness the form of the shoals below them, appearing to the eye as the aerial reflection of the bottom of the sea. A still more striking effect of the cooling produced by shoals is manifested in the higher strata of air, in a somewhat analogous manner to that observed in the case of flat coral reefs, or sand islands. In the open sea, far from the land, and when the air is calm, clouds are often observed to rest over the spots where shoals are situated, and their bearing may then be taken by the compass in the same manner as that of a high mountain or isolated peak.

Although the surface of the ocean is less rich in living forms than that of continents, it is not improbable that, on a further investigation of its depths, its interior may be found to possess a greater richness of organic life than any other portion of our planet. Charles Darwin, in the agreeable narrative of his extensive voyages, justly remarks that our forests do not conceal so many animals as the low woody regions of the ocean, where the sea-weed rooted to the bottom of the shoals, and the severed branches of fuci, loosened by the force of the waves and currents, and swimming free, unfold their delicate foliage, upborne by air-cells.*

The application of the microscope increases, in the most striking manner, our impression of the rich luxuriance of animal life in the ocean, and reveals to the astonished senses a consciousness of the universality of life. In the oceanic depths, far exceeding the height of our loftiest mountain chains, every stratum of water is animated with polygastric sea-worms, Cyclidiae and Ophrydinae. The waters swarm with countless hosts of small luminiferous animalcules, Mammaria (of the order of Acalephae), Crustacea, Peridinea, and circling Nereides, which when attracted to the surface by peculiar meteorological conditions, convert every wave into a foaming band of flashing light.

p 310 The abundance of those marine animalcules, and the animal matter yielded by their rapid decomposition are so vast that the sea water itself becomes a nutrient fluid to many of the larger animals. However much this richness in animated forms, and this multitude of the most various and highly-developed microscopic organisms may agreeably excite the fancy, the imagination is even more seriously, and, I might say, more solemnly moved by the impression of boundlessness and immeasureability, which are presented to the mind by every sea voyage. All who possess an ordinary degree of mental activity, and delight to create to themselves an inner world of thought, must be penetrated with the sublime image of the infinite, when gazing around them on the vast and boundless sea, when involuntarily the glance is attracted to the distant horizon, where air and water blend together, and the stars continually rise and set before the eyes of the mariner. This contemplation of the eternal play of the elements is clouded, like every human joy, by a touch of sadness and of longing.

A peculiar predilection for the sea, and a grateful remenbrance of the impression which it has excited in my mind, when I have seen it in the tropics in the calm of nocturnal rest, or in the fury of the tempest, have alone induced me to speak of the individual enjoyment afforded by its aspect before I entered upon the consideration of the favorable influence which the proximity of the ocean has incontrovertibly exercised on the cultivation of the intellect and character of many nations, by the multiplication of those bands which ought to encircle the whole of humanity, by affording additional means of arriving at a knowledge of the configuration of the earth, and furthering the advancement of astronomy, and of all other mathematical and physical sciences. A portion of this influence was at first limited to the Mediterranean and the shores of southwestern Africa, but from the sixteenth century it has widely spread, extending to nations who live at a distance from the sea, in the interior of continents. Since Columbus was sent to "unchain the ocean"* (as the unknown voice whispered to him in a dream when he lay on a sick-bed near p 311 the River Belem), man has ever boldly ventured onward toward the discovery of unknown regions.

The second external and general covering of our planet, the aerial ocean, in the lower strata, and on the shoals of which we live, presents six classes of natural phenomena, which manifest the most intimate connection with one another. They are dependent on the chemical composition of the atmosphere, the variations in its transparency, polarization, and color, its density or pressure, its temperature and humidity, and its electricity. The air contains in oxygen the first element of physical animal life, and besides this benefit, it possesses another, which may be said to be of a nearly equally high character, namely, that of conveying sound; a faculty by which it likewise becomes the conveying sound; a faculty by which it likewise becomes the conveyer of speech and the means of communicating thought, and consequently of maintaining social intercourse. If the Earth were deprived of an atmosphere, as we suppose our moon to be, it would present itself to our imagination as a soundless desert.

The relative quantities of the substances composing the strata of air accessible to us have, since the beginning of the nineteenth century, become the object of investigations, in which Gay-Lussac and myself have taken an active part; it is however, only very recently that the admirable labors of Dumas and Boussingault have, by new and more accurate methods, brought the chemical analysis of the atmosphere to a high degree of perfection. According to this analysis, a volume of dry air contains 20.8 of oxygen, and 79.2 of nitrogen, besides from two to five thousandth parts of carbonic acid gas, a still smaller quantity of carbureted hydrogen gas,* and, according to the important experiments of Saussure and Liebig, traces of ammoniacal vapors,** from which plants derive their nitrogenous contents.

Some observations of Lewy render it probable that the quantity of oxygen varies perceptibly p 312 but slightly, over the sea and in the interior of continents, according to local conditions or to the seasons of the year. We may easily conceive that changes in the oxygen held in solution in the sea, produced by microscopic animal organisms, may be attended by alterations in the strata of air in immediate contact with it.*

The air which Martins collected at Faulhorn at an elevation of 8767 feet, contained as much oxygen as the air at Paris.*

The admixture of carbonate of ammonia in the atmosphere may probably be considered as older than the existence of organic beings on the surface of the earth. The sources from which carbonic acid* may be yielded to the atmosphere are most numerous.

In the first place we would mention the respiration of animals, who receive the carbon which they inhale from vegetable food, while vegetables receive it from the atmosphere; in the next place, carbon is supplied from the interior of the earth in the vicinity of exhausted volcanoes and thermal springs, from the decomposition of a small quantity of carbureted hydrogen gas in the atmosphere, and from the electric discharges of clouds, which are of such frequent occurrence within the tropics. Besides these substances, which we have considered as appertaining to the atmosphere at all heights that are accessible to us, there are others accidentally mixed with them, especially near the ground, which sometimes, in the form of miasmatic and gaseous contagia, exercise a noxious influence on animal organization. Their chemical nature has not yet been ascertained by direct analysis; but, from the consideration of the processes of decay which are perpetually going on in the animal and vegetable substances with which the surface of our planet is covered, and judging from analogies deduced from the comain of pathology, we are led to infer the existence of such noxious local admixtures. Ammoniacal and other nitrogenous vapors, sulphureted hydrogen gas, and compounds analogous to the polybasic ternary and quaternary compounds analogous to the polybasic ternary and quaternary combinations of the vegetable kingdom, may produce miasmata,* p 313 which, under various forms, may generate ague and typhus fever (not by any means exclusively on wet, marshy ground, or on coasts covered by putrescent mollusca, and low bushes of 'Rhizophora mangle' and Avicennia).

Fogs which have a peculiar smell at some seasons of the year, remind us of these accidental admixtures in the lower strata of the atmosphere. Winds and currents of air caused by the heating of the ground even carry up to a considerable elevation solid substances reduced to a fine powder. The dust which darkens the air for an extended area, and falls on the Cape Verd Islands, to which Darwin has drawn attention, contains, according to Ehrenberg's discovery, a host of silicious-shelled infusoria.

As principal features of a general descriptive picture of the atmosphere, we may enumerate:

1. 'Variations of atmospheric pressure': to which belong the horary oscillations, occurring with such regularity in the tropics, where they produce a kind of ebb and flow in the atmosphere, which can not be ascribed to the attraction of the moon,* and which differs so considerably according to geographical latitude, the seasons of the year, and the elevation above the level of the sea.

2. 'Climatic distribution of heat', which depends on the relative position of the transparent and opaque masses (the fluid and solid parts of the surface of the earth), and on the hypsometrical configuration of continents; relations which determine the geographical position and curvature of the isothermal lines (or curves of equal mean annual temperature) both in a horizontal and vertical direction, or on a uniform plane, or in different superposed strata of air.

3. 'The distribution of the humidity of the atmosphere'. The quantitative relations of the humitidy depend on the differences in the solid and oceanic surfaces; on the distance from the equator and the level of the sea; on the form in which the p 314 aqueous vapor is precipitated, and on the connection existing between these deposits and the changes of temperature, and the direction and succession of winds.

4. 'The electric condition of the atmosphere'. the primary cause of this condition, when the heavens are serene, is still much contested. Under this head we must consider the relation of ascending vapors to the electric charge and the form of the clouds, according to the different periods of the day and year; the difference between the cold and warm zones of the earth, or low and high lands; the frequency or rarity of thunder storms, their periodicity and formation in summer and winter; the causal connection of electricity, with the infrequent occurrence of hail in the night, and with the phenomena of water and sand spouts, so ably investigated by Peltier.

The horary oscillations of the barometer, which in the tropics present two maxima (viz., at 9 or 9 1/4 P.M., and 4 A.M., occurring, therefore, in almost the hottest and coldest hours), have long been the object of my most careful diurnal and nocturnal observations.*

Their regularity is so great, that, in the daytime especially, the hour may be ascertained from the height of the mercurial column without an error, on the average, of more than fifteen or seventeen minutes. In the torrid zones of the New Continent, on the coasts as well as at elevations of nearly 13,000 feet above the level of the sea, where the mean temperature falls to 44.6 degrees, I have found the regularity of the ebb and flow of the aerial ocean undisturbed by storms, hurricanes, rain, and earthquakes. The amount of the daily oscillations diminishes from 1.32 to 0.18 French lines from the equator to 70 degrees north latitude, where Bravais made very accurate observations at Bosekop.*

The supposition that, much nearer the pole, the height of the barometer is really less at 10 A.M. than at 4 P.M., and consequently, that the maximum and minimum influences of these hours p 315 are inverted, is not confirmed by Parry's observations at Port Bowen (73 degrees 14').

The mean height of the barometer is somewhat less under the equator and in the tropics, owing to the effect of the rising current,* than in the temperate zones, and it appears to attain its maximum in Western Europe between the parallels of 40 degrees and 45 degrees.

If with Kämtz we connect together by 'isobarometric' lines those places which present the same mean difference between the monthly extremes of the barometer, we shall have curves whose geographical position and inflections yield important conclusions regarding the influence exercised by the form of the land and the distribution of seas on the oscillations of the atmosphere. Hindostan with its high mountain chains and triangular peninsulas, and the eastern coasts of the New Continent, where the warm Gulf Stream turns to the east at the Newfoundland Banks, exhibit greater isobarometric oscillations than do the group of the Antilles and Western Europe. The prevailing winds exercise a principal influence on the diminution of the pressure of the atmosphere, and this, as we have already mentioned, is accompanied, according to Daussey, by an elevation of the mean level of the sea.•

As the most important fluctuations of the pressure of the atmosphere, whether occurring with horary or annual regularity, or accidentally, and then often attended by violence and danger,* are like all the other phenomena of the weather, mainly owing to the heating force of the sun's rays, it has long been suggested (partly according to the idea of Lambert) that the direction of the wind should be compared with the height of the barometer, alternations of temperature, and the increase and decrease of humidity.

Tables of atmospheric pressure during different winds, termed 'barometric windroses', afford a deeper insight into the connection of meteorological phenomena.*

Dove has, with admirable sagacity, recognized, in the "law of rotation" in both hemispheres, which he himself established, the cause of many important processes in the aerial ocean.*

The difference of temperature between the p 315 equatorial and polar regions engenders two opposite currents in the upper strata of the atmosphere and on the Earth's surface. Owing to the difference between the rotatory velocity at the poles and at the equator, the polar current is deflected eastward, and the equatorial current westward. The great phenomena of atmospheric pressure, the warming and cooling of the strata of air, the aqueous deposits, and even, as Dove has correctly represented, the formation and appearance of clouds, alike depend on the opposition of these two currents, on the place where the upper one descends, and on the displacement of the one by the other. Thus the figures of the clouds, which form an animated part of the charms of a landscape, announce the processes at work in the upper regions of the atmosphere, and, when the air is calm, the clouds will often present, on a bright summer sky, the "projected image" of the radiating soil below.

Where this influence of radiation is modified by the relative position of large continental and oceanic surfaces, as between the eastern shore of Africa and the western part of the Indian peninsula, its effects are manifested in the Indian monsoons, which change with the periodic variations in the sun's declination,* and which were known to the Greek navigators under the name of 'Hippalos'.

In the knowledge of the monsoons, which undoubtedly dates back thousands of years among the inhabitants of Hindostan and China, of the eastern parts of the Arabian Gulf and of the western shores of the Malayan p 317 Sea, and in the still more ancient and more general acquaintance with land and sea winds, lies concealed, as it were, the germ of that meteorological sciences which is now making such rapid progress. The long chain of 'magnetic stations' extending from Moscow to Pekin, across the whole of Northern Asia, will prove of immense importance in determining the 'law of the winds', since these stations have also for their object the investigation of general meteorological relations. The comparison of observations made at places lying so many hundred miles apart, will decide, for instance, whether the same east wind blows from the elevated desert of Gobi to the interior of Russia, or whether the direction of the Aerial current first began in the middle of the series of the stations, by the descent of the air from the higher regions. By means of such observations, we may learn, in the strictest sense, 'whence' the wind cometh. If we only take the results on which we may depend from those places in which the observations on the direction of the winds have been continued more than twenty years, we shall find (from the most recent and careful calculations of Wilhelm Mahlmann) that in the middle latitudes of the temperate zone, in both continents, the prevailing aerial current has a west-southwest direction.

Our insight into the 'distribution of heat' in the atmosphere has been rendered more clear since the attempt has been made to connect together by lines those places where the mean annual summer and winter temperatures have been ascertain by correct observations. The system of 'isothermal, osotheral' and 'isochimenal' lines, which I first brought into use in 1817, may, perhaps, if it be gradually perfected by the united efforts of investigators, serve as one of the main foundations of 'comparative climatology'. Terrestrial magnetism did not acquire a right to be regarded as a science until partial results were graphically connected in a system of lines of 'equal declination, equal inclinatiion', and 'equal intensity'.

The term 'climate', taken in its most general sense, indicated all the changes in the atmosphere which sensibly affect our organs, as temperature, humidity, variations in the barometrical pressure, the calm state of the air or the action of opposite winds, the amount of electric tension, the purity of the atmosphere or its admixture with more or less noxious gaseous exhalations, and, finally, the degree of ordinary transparency and clearness of the sky, which is not only important with respect to the increased radiation from the Earth, the organic development of plants, and the ripening of fruits, but p 318 also with reference to its influence on the feelings and mental condition of men.

If the surface of the Earth consisted of one and the same homogeneous fluid mass, or of strata of rock having the same color, density, smoothness, and power of absorbing heat from the solar rays, and of radiating it in a similar manner through the atmosphere, the isothermal, isotheral, and isochimenal lines would all be parallel to the equator. In this hypothetical condition of the Earth's surface, the power of absorbing and emitting light and heat would every where be the same under the same latitudes. The mathematical consideration of climate, which does not exclude the supposition of the existence of currents of heat in the interior, or in the external crust of the earth, nor of the propagation of heat by atmospheric currents, proceeds from this mean, and, as it were, primitive condition. Whatever alters the capacity for absorption and radiation, at places lying under the same parallel of latitude, gives rise to inflections in the isothermal lines. The nature of these inflections, the angles at which the isothermal, isotheral, or isochimenal lines intersect the parallels of latitude, their convexity or concavity with respect to the pole of the same hemisphere, are dependent on causes which more or less modify the temperature under different degrees of longitude.

The progress of 'Climatology' has been remarkably favored by the extension of European civilization to two opposite coasts, by its transmission from our western shores to a continent which is bounded on the east by the Atlantic Ocean. When, after the ephemeral colonization from Iceland and Greenland, the British laid the foundation of the first permanent settlements on the shores of the United States of America, the emigrants (whose numbers were rapidly increased in consequence either of religious persecution, fanaticism, or love of freedom, and who soon spread over the vast extent of territory lying between the Carolinas, Virginia, and the St. Lawrence) were astonished to find themselves exposed to an intensity of winter cold far exceeding that which prevailed in Italy, France, and Scotland, situated in corresponding parallels of latitude. But, however much a consideration of these climatic relations may have awakened attention, it was not attended by any practical results until it could be based on the numerical data of 'mean annual temperature'. If, between 58 degrees and 30 degrees north latitude, we compair Nain, on the coast of Labrador, with Gottenburg; Halifax with Bordeaus; New p 319 York with Naples; St. Augustine, in Florida, with Cairo, we find that, under the same degrees of latitude, the differences of the mean annual temperature between Eastern America and Western Europe, proceeding from north to south, are successively 20.7 degrees, 13.9 degrees, 6.8 degrees, and almost 0 degrees. The gradual decrease of the differences in this series extending over 28 degrees of latitude is very striking. Further to the south, under the tropics, the isothermal lines are every where parallel to the equator in both hemispheres. We see, from the above examples, that the questions often asked in society, how many degrees America (without distinguishing between the eastern and western shores) is colder than Europe? and how much the mean annual temperature of Canada and the United States is lower than that of corresponding latitudes in Europe? are, when thus 'generally expressed', devoid of meaning. There is a separate difference for each parallel of latitude, and without a special comparison of the winter and summer temperatures of the opposite coasts, it will be impossible to arrive at a correct idea of climatic relations, in their influence on agriculture and other industrial pursuits, or on the individual comfort or discomfort of manking in general.

In enumerating the causes which produce disturbances in the form of the isothermal lines, I would distinguish between those which 'raise' and those which 'lower' the temperature. To the first class belong the proximity of a western coast in the temperate zone; the divided configuration of a continent into peninsulas, with deeply-indented bays and inland seas; the aspect of the position of a portion of the land with reference either to a sea of ice spreading far into the polar circle, or to a mass of continental land of considerable extent, lying in the same meridian, either under the equator, or, at least, within a portion of the tropical zone; the prevalence of southerly or westerly winds on the western shore of a continent in the temperate northern zone; chains of mountains acting as protecting salls against the winds coming from colder regions; the infrequency of swamps, which, in the spring and beginning of summer, long remain covered with ice, and the absence of woods in a dry, sandy soil; finally the constant serenity of the sky in the summer months, and the vicinity of an oceanic current, bringing water which is of a higher temperature than that of the surrounding sea.

Among the causes which tend to 'lower' the mean annual temperature I include the following: elevation above the level of the sea, when not forming part of an extended plain; the p 320 vicinity of an eastern coast in high and middle latitudes; the compact configuration of a continent having no littoral curvatures or bays; the extension of land toward the poles into the region of perpetual ice, without the intervention of a sea remaining open in the winter; a geographical position, in which the equatorial and tropical regions are occupied by the sea, and consequently, the absence, under the same meridian, of a continental tropical land having a strong capacity for the absorption and radiation of heat; mountain chains, whose mural form and direction impede the access of warm winds, the vicinity of isolated peaks, occasioning the descent of cold currents of air down their declivities; extensive woods, which hinder the isolation of the soil by the vital activity of their foliage, which produces great evaporation, owing to the extension of these organs, and increases the surface that is cooled by radiation, acting consequently in a three-fold manner, by shade, evaporation, and radiation; the frequency of swamps or marshes, which in the north form a kind of subterranean glacier in the plains, lasting till the middle of the summer; a cloudy summer sky, which weakens the action of the solar rays; and, finally, a very clear winter sky, favoring the radiation of heat.*

The simultaneous action of these disturbing causes, whether productive of an increase or decrease of heat, determines, as the total effect, the inflection of the isothermal lines, especially with relation to the expansion and configuration of solid continental masses, as compared with the liquid oceanic. These perturbations give rise to convex and concave summits of the isothermal curves. There are, however, different orders of disturbing causes, and each one must, therefore, be considered separately, in order that their total effect may afterward be investigated with reference to the motion (direction, local curvature) of the isothermal lines, and the actions by which they are connected together, modified, destroyed, or increased in intensity, as manifested in the contact and intersection of small oscillatory movements. Such is the method by which, I hope, it may some day be possible to connect together, by empirical and numerically expressed laws, vast series of apparently isolated facts, and to exhibit the mutual dependence which must necessarily exist among them.

The trade winds -- easterly winds blowing within the tropics -- give rise, in both temperate zones, to the west, or west-southwest p 321 sinds which prevail in those regions, and which are land winds to eastern coasts, and sea winds to western coasts, estending over a space which, from the great mass and the sinking of its cooled particles, is not capable of any considerable degree of cooling, and hence it follows that the east winds of the Continent must be cooler than the west winds, where their temperature is not affected by the occurrence of oceanic currents near the shore. Cook's young companion on his second voyage of circumnavigation, the intelligent George Forster, to whom I am indebted for the lively interest which prompted me to undertake distant travels, was the first who drew attention, in a definite manner, to the climatic differences of temperature existing in the eastern and western coasts of both continents, and to the similarity of temperature of the western coast of North America in the middle latitudes, with that of Western Europe.*

Even in northern latitudes exact observations show a striking difference between the 'mean annual temperature' of the east and west coasts of America. The mean annual temperature of Nain, in (lat. 57 degrees 10'), is fully 6.8 degrees 'below' the freezing point, while on the northwest coast, at New Archangel, in Russian America (lat. 57 degrees 3'), it is 12.4 degrees 'above' this point. At the first-named place, the mean summer temperature hardly amounts to 43 degrees, while at the latter place it is 57 degrees. Pekin (39 degrees 54'), on the eastern coast of Asia, has a mean annual tempeerature of 52.8 degrees, which is 9 degrees below that of Naples, situated somewhat further to the north. The mean winter temperature of Pekin is at least 5.4 degrees below the freezing point, while in Western Europe, even at Paris (48 degrees 50'), it is nearly 6 degrees above the freezing point. Pekin has also a mean winter cold which is 4.5 degrees lower than that of Copenhagen, lying 17 degrees further to the north.

We have already seen the slowness with which the great mass of the ocean follows the variations of temperature in the atmosphere, and how the sea acts in equalizing temperatures, moderating simultaneously the severity of winter and the heat of summer. Hence arises a second more important contrast -- that, namely, between insular and littoral climates enjoyed by all articulated continents having deeply indented bays and peninsulas, and between the climate of the interior of great masses of solid land. This remarkable contrast has been fully p 322 developed by Leopold von Buch in all its various phenomena, both with respect to its influence on vegetation and agriculrure, on the transparency of the atmosphere, the radiation of the soil, and the elevation of the line of perpetual snow. In the interior of the Asiatic Continent, Tobolsk, Barnaul on the Oby, and Irkutsk, have the same mean summer heat as Berlin, Munster, and Cherbourg in Normandy, the thermometer sometimes remaining for weeks together at 86 degrees or 88 degrees, while the mean winter temperature is, during the coldest month, as low as -0.4 degrees to -4 degrees. These continental climates have therefore justly been termed 'excessive' by the great mathematician and physicist Buffon; and the inhabitants who live in countries having such 'excessive' climates seem almost condemned, as Dante expresses himself, "A sofferir tormenti caldi e geli."*

In no portion of the earth, neither in the Canary Islands, in Spain, nor in the south of France, have I ever seen more luxuriant fruit, especially grapes, than in Astrachan, near the shores of the Caspian Sea (46 degrees 21'). Although the mean annual temperature is about 48ºdegrees, the mean summer heat rises to 70ºdegrees, as at Bordeaux, while not only there, but also further to the south, as at Kislar on the mouth of the Terek (in the latitude of Avignon and Rimini), the thermometer sinks in the winter to -13 degrees or -22 degrees.

Ireland, Guernsey, and Jersey, the peninsula of Brittany, the coasts of Normandy, and of the south of England, present, by the mildness of their winters, and by the low temperature and clouded sky of their summers, the most striking contrast to the continental climate of the interior of Eastern Europe. In the northeast of Ireland (54 degrees 56'), lying under the same parallel of latitude as Konigsberg in Prussia, the myrtle blooms as luxuriantly as in Portugal. The mean temperature of the month of August, which in Hungary rises to 70 degrees, scarcely reaches 61 degrees at Dublin, which is situated on the same isothermal line of 49 degrees; the mean winter temperature, which falls to about 28 degrees at Pesth, is 40 degrees at Dublin (whose mean annual temperature is not more than 49 degrees); 3.6 degrees higher than that of Milan, Pavia, Padua, and the whole of Lombardy, where the mean annual temperature is upward of 55ºdegrees. At Stromness, in the Orkneys, scarcely half a degree further south than Stockholm, the winter temperature is 39 degrees, and consequently higher than that of Paris, and neary as high as that of London. p 323 Even in the Faroe Islands, at 62 degrees latitude, the inland waters never freeze, owing to the favoring influence of the west winds and of the sea. On the charming coasts of Devonshire, near Salcombe Bay, which has been termed, on account of the mildness of its climate, the 'Montpellier of the North', the Agave Mexicana has been seen to blossoom in the open air, while orange-trees trained against espaliers, and only slightly protected by matting, are found to bear fruit. There, as well as at Penzance and Gosport, and at Cherbourg on the coast of Normandy, the mean winter temperature exceeds 42 degrees, falling short by only 2.4 degrees of the mean winter temperature of Montpellier and Florence.*

These observations will suffice to show the important influence exercised on vegetation and agriculture, on the cultivation of fruit, and on the comfort of mankind, by differences in the distribution of the same mean annual temperature, through the different seasons of the year.

The lines which I have termed 'Isochimenal' and 'isotheral' (lines of equal winter and equal summer temperature) are by no means parallel with the 'isothermal' lines (lines of equal annual temperature). If, for instance, in countries where myrtles grow wild, and the earth does not remain covered with snow in the winter, the temperature of the summer and autumn is barely sufficient to bring apples to perfect ripeness, and if, again, we observe that the grape rarely attains the ripeness necessary to convert it into wine, either in islands or in the vicinity of the sea, even when cultivated on a western coast, the reason must not be sought only in the low degree of summer heat, indicated, in littoral situations, by the thermometer when suspended in the shade, but likewise in another cause that has not hitherto been sufficiently considered, although it exercises an active influence on many other phenomena (as, for instance, in the inflammation of a mixture of chlorine and hydrogen), namely the difference between direct and diffused light, or that which prevails when the sky is clear and when it is overcast by mist. I long since endeavored to attract the attention of physicists and physiologists* to this p 324 difference, and to the 'unmeasured' heat which is locally developed in the living vegetable cell by the action of direct light.

If, in forming a thermic scale of different kinds of cultivation,* we begin with those plants which require the hottest climate, as the vanilla, the cacao, banana, and cocoa-nut, and proceed to the pine-apples, the sugar-cane, coffee, fruit-bearing date-trees, the cotton-tree, citrons, olives, edible chestnuts, and fines producing potable wine, an exact geographical consideration of the limits of cultivation, both on plains and on the declivities of mountains, will teach us that other climatic relations besides those of mean annual temperature are involved in these phenomena.

Taking an example, for instance, from the cultivation of the vine, we find that, in order to procure 'potable' wine,* it is requisite that the mean annual heat should exceed 49 degrees, that the winter temperature upward of 64 degrees.

_____________________________________________________________________ Places. Lat- Ele- Mean Win- Spring. Sum- Aut- Number of the it- va- of the ter. mer. umn. years of the tude tion. Year. observation

_____________________________________________________________________ deg ' Eng.ft. Fahr.

Bordeaux 44 50 25.6 57.0 43.0 56.0 71.0 58.0 10 Stras- 48 35 479.0 49.6 34.5 50.0 64.6 50.0 35 bourg Heid- 49 24 333.5 59.5 34.0 50.0 64.3 49.7 20 elberg Manheim 49 29 300.5 50.6 34.6 50.8 67.1 49.5 12 Wurzburg 49 48 562.5 50.2 35.5 50.5 65.7 49.4 27 Frank- fort on Maine 50 7 388.5 49.5 33.3 50.0 64.4 49.4 19 Berlin 52 31 102.3 47.5 31.0 46.6 63.6 47.5 23 Cher- bourg (no wine) 49 39 .... 52.1 41.5 50.8 61.7 54.2 3 Dublin (ditto) 53 23 .... 49.1 40.2 47.1 59.6 49.7 13 ___________________________________________________________________

The great accordance in the distribution of the annual temperature through the different seasons, as presented by the results obtained for the valleys of the Rhine and Maine, tends to confirm the accuracy of these meteorological observations. The months of December, January, and February are reckoned as winter months. When the different qualities of the wines produced in Franconia, and in the countries around the Baltic, are compared with the mean summer and autumn temperature of Wurzburg and Berlin, we are almost surprised to find a difference of only about two degrees. The difference in the spring is about four degrees. The influence of late May frosts on the flowering season, and after a correspondingly cold winter, is almost as important an element as the time of the subsequent ripening of the grape. The difference alluded to in the text between the true temperature of the surface of the ground and the indications of a thermometer suspended in the shade and protected from extraneous influences, is inferred by Dove from a consideration of the results of fifteen years' observations made at the Chiswick Gardens. See Dove, in 'Bericht uber die Verhandl. der Berl. Akad. der Wiss.', August, 1844, s. 285.

At Bordeaux, in the valley of the Garonne (44 degrees 50' lat.), the mean annual winter, summer, and autumn temperatures are respectively 57 degrees, 43 degrees, 71 degrees, and 58 degrees. In the plains near the p 325 Baltic (52 degrees 30' lat.), where a wine is produced that can scarcely be considered potable, these numbers are as follows: 47.5 degrees, 30 degrees, 63.7 degrees, and 47.5 degrees. If it should appear strange that the great differences indicated by the influence of climate on the production of wine should not be more clearly manifested by our thermometers, the circumstance will appear less singular when we remember that a thermometer standing in the shade, and protected from the effect of direct insolation and nocturnal radiation can not, at all seasong of the year, and during all periodic changes of heat, indicate the true superficial temperature of the ground exposed to the whole effect of the sun's rays.

The same relations which exist between the equable littoral climate of the peninsula of Brittany, and the lower winter and p 326 higher summer temperature of the remainder of the continent of France, are likewise manifested in some degree, between Europe and the great continent of Asia, of which the former may be considered to constitute the western peninsula. Europe owes its milder climate, in the first place, to its position with respect to Africa, whose wide extent of tropical land is favorable to the ascending current, while the equatorial region to the south of Asia is almost wholly oceanic; and next to its deeply-articulated configuration, to the vicinity of the ocean on its western shores; and, lastly, to the existence of an open sea, which bounds its northern confines. Europe would therefore become colder* if Africa were to be overflowed by the ocean; of if the mythical Atlantis were to arise and connect Europe with North America; or if the Gulf Stream were no longer to diffuse the warming influence of its waters into the North Sea; or if, finally, another mass of solid land should be upheaved by volcanic action, and interposed between the Scandinavian peninsula and Spitzbergen.

If we observe that in Europe the mean annual temperature falls as we proceed, from west to east, under the same parallel of latitude, from the Atlantic shores of France through Germany, Poland, and Russia, toward the Uralian Mountains, the main cause of this phenomenon of increasing cold must be sought in the form of the continent (which becomes less indented, and wider, and more compact as we advance), in the increasing distance from seas, and in the diminished influence of westerly winds. Beyond the Uralian Mountains these winds are converted into cool land-winds, blowing over extended tracts covered with ice and show. The cold of western Siberia is to be ascribed to these relations of configuration and atmospheric currents, and not -- as Hippocrates and Trogus Pompeius, and even celebrated travelers of the eighteenth century conjectures -- to the great elevation of the soil above the level of the sea.*

If we pass from the differences of temperature manifested in the plains to the inequalities of the polyhedric form of the surface of our planet, we shall have to consider mountains either in relation to their influence on the climate of neighboring p 327 valleys, or according to the effects of the hyposometrical relations on their own summits, which often spread into elevated plateaux. The division of mountains into chains separates the earth's surface into different basins, which are often narrow and walled in, forming caldron-like valleys, and (as in Greece and in part of Asia Minor) constitute an individual local climate with respect to heat, moisture, transparancy of atmosphere, and frequency of winds and storms. These circumstances have at all times exercised a powerful influence on the character and cultivation of natural products, and on the manners and institutions of neighboring nations, and even on the feelings with which they regard one another. This character of 'geographical individuality' attains its maximum, if we may be allowed so to speak, in countries where the differences in the configuration of the soil are the greatest possible, either in a vertical or horizontal direction, both in relief and in the articulation of the continent. The greatest contrast to these varieties in the relations of the surface of the earth are manifested in the Steppes of Northern Asia, the grassy plains (savannahs, llanos, and pampas) of the New Continent, the heath ('Ericeta') of Europe, and the sandy and stony deserts of Africa.

The law of the decrease of heat with the increase of elevation at different latitudes is one of the most important subjects involved in the study of meteorological processes, of the geography of plants, of the theory of terrestrial refraction, and of the various hypotheses that relate to the determination of the height of the atmosphere. In the many mountain journeys which I have undertaken, both within and without the tropics, the investigation of this law has always formed a special object of my researches.*

Since we have acquired a more accurate knowledge of the true relations of the distribution of heat on the surface of the earth, that is to say, of the inflections of isothermal and isotheral lines, and their unequal distance apart in the different eastern and western systems of temperature in Asia, Central Europe, and North America, we can no longer ask the general question, what fraction of the mean annual or summer temperature corresponds to the difference of one degree of geographical latitude, taken in the same meridian? In each system of 'isothermal' lines of equal curvature there reigns a p 328 close and necessary connection between three elements, namely, the decrease of heat in a vertical direction from below upward, the difference of temperature for every one degree of geographical latitude, and the uniformity in the mean temperature of a mountain station, and the latitude of a point situated at the level of the sea.

In the system of Eastern America, the mean annual temperature from the coast of Labrador to Boston changes 1.6ºdegrees for every degree of latitude; from Boston to Charleston about 1.7 degrees; from Charleston to the tropic of Cancer, in Cuba, the variation is less rapid, being only 1.2 degrees. In the tropics this diminution is so much greater, that from the Havana to Cumana the variation is less than 0.4 degrees for every degree of latitude.

The case is quite different in the isothermal system of Central Europe. Between the parallels of 38 degrees and 71 degrees I found that the decrease of temperature was very regularly 0.9degrees for every degree of latitude. But as, on the other hand, in Central Europe the decrease of heat is 1.8 degrees for about every 534 feet of vertical elevation, it follows that a difference of elevation of about 267 feet corresponds to the difference of one degree of latitude. The same mean annual temperature as that occurring at the Convent of St. Bernard, at an elevation of 8173 feet, in lat. 45 degrees 50' should therefore be met with at the level of the sea in lat. 75 degrees 50'.

In that part of the Cordilleras which falls within the tropics, the observations I made at various heights, at an elevation of upward of 19,000 feet, gave a decrease of 1 degree for every 341 feet; and my friend Boussingault found, thirty years afterward, as a mean result, 319 feet. By a comparison of places in the Cordilleras, lying at an equal elevation above the level of the sea, either on the declivities of the mountains or even on extensive elevated plateaux, I observed that in the latter there was an increase in the annual temperature varying from 2.7 degrees to 4.1 degrees. This difference would be still greater if it were not for the cooling effect of nocturnal radiation. As the different climates are arranged in successive strata, the one above the other, from the cacao woods of the valleys to the region of perpetual snow, and as the temperature in the tropics varies but little throughout the year, we may form to ourselves a tolerably correct representation of the climatic relations to which the inhabitants of the large cities in the Andes are subjected, by comparing these climates with the temperatures of particular months in the plains of France and Italy. While p 329 the heat which prevails daily on the woody shores of the Orinoco exceeds by 7.2 degrees that of the month of August at Palermo, we find, on ascending the chain of the Andes, at Popayan, at an elevation of 3826 feet, the temperature of the three summer months of Marseilles; at Quito, at an elevation of 9541 feet, that of the close of May at Paris; and on the Paramos, at a height of 11,510 feet, where only stunted Alpine shrubs grow, though flowers still bloom in abundance, that of the beginning of April at Paris. The intelligent observer, Peter Martyr de Aughiera, one of the friends of Christopher Columbus, seems to have been the first who recognized (in the expedition undertaken by Rodrigo Enrique Colmenares, in October, 1510) that the limit of perpetual snow continues to ascend as we approach the equator. We read, in the fine work 'De Rebus Oceanicis',* "the River Gaira comes from a mountain in the Sierra Nevada de Santa Maria, which, according to the testimony of the companions of Colmenares, is higher than any other mountain hitherto discovered.

It must undoubtedly be so if 'it retain snow perpetually' in a zone which is not more than 10 degrees from the equinoctial line." The lower limit of perpetual snow, in a given latitude, is the lowest line at which snow continues during summer, or, in other words, it is the maximum of height to which the snow-line recedes in the course of the year. But this elevation must be distinguished from three other phenomena, namely, the annual fluctuation of the snow-line, the occurrence of sporadic falls of snow, and the existence of glaciers, which appear to be peculiar to the temperate and cold zones. This last phenomenon, since Saussure's immortal work on the Alps, has received much light, in recent times, from the labors of Venetz, Charpentier, and the intrepid and persevering observer Agassiz.

We know only the 'lower', and not the 'upper' limit of perpetual snow; for the mountains of the earth do not attain to those ethereal regions of the rarefied and dry strata of air, in which we may suppose, with Bouguer, that the vesicles of aqueous vapor are converted into crystals of ice, and thus rendered perceptible to our organs of sight. The lower limit of snow is not, however, a mere function of geographical latitude or of mean annual temperature; nor is it at the equator, or p 330 even, in the region of the tropics, that this limit attains its greatest elevation above the level of the sea. The phenomenon of which we are treating is extremely complicated, depending on the general relations of temperature and humidity, and on the form of the mountains. On submitting these relations to the test of special analysis, as we may be permitted to do from the number of determinations that have recently been made,* we shall find that the controlling causes are the differences in the temperature of different seasons of the year; the direction of the prevailing winds and their relations to this land and sea; the degree of dryness or humitidy in the upper strata of the air; the absolute thickness of the accumulated masses of fallen snow; the relation of the s-line to the total height of the mountain; the relative position of the latter in the chain to which it belongs, and the steepness of its declivity; the vicinity of either summits likewise perpetually covered with show; the expansion, position, and elevation of the plains from which the snow mountain rises as an isolated peak or as a portion of a chain; whether this plain be part of the sea-coast, or of the interior of a continent; whether it be covered with wood or waving grass; and whether, finally, it consist of a dry and rocky soil, or of a wet and marshy bottom.

The snow-line which, under the equator in South America, attains an elevation equal to that of the summit of Mont Blanc in the Alps, and descends, according to recent measurements, about 1023 feet lower toward the northern tropic in the elevated plateaux of Mexico (in 19 degrees north latitude), rises, according to Pentland, in the southern tropical zone (14 degrees 30' to 18 degrees south latitude), being more than 2665 feet higher in the maritime and western branch of the Cordilleras of Chili than under the equator near Quito on Chimborazo, Cotopaxi, and Antisana. Dr. Gilles even asserts that much further to the south, on the declivity of the volcano of Peuquenes (latitude 33 degrees), he found the snow-line at an elevation of between 14,520 and 15,030 feet. The evaporation of the snow in the extremely dry air of the summer, and under a cloudless sky, is so powerful, that the volcano of Aconcagua, northeast of Valparaiso (latitude 32 degrees 30'), which was found in the expedition of the Beagle to be more than 1400 feet higher than Chimborazo, was on one occasion seen free from snow.•

In p 331 an almost equal northern latitude (from 30 degrees 45' to 31 degrees), the snow'line on the southern declivity of the Himalaya lies at an elevation of 12,982 feet, which is about the same as the height which we might have assigned to it from a comparison with other mountain chains; on the northern declivity, however, under the influence of the high lands of Thibet (whose mean elevation appears to be about 11,510 feet), the snow-line is situated at a height of 16,630 feet. This phenomenon, which has long been contested both in Europe and in India, and whose causes I have attempted to develop in various works, published since 1820,* possesses other grounds of interest than p 332 those of a purely physical nature, since it exercises no inconsiderable degree of influence on the mode of life of numerous tribes -- the meteorological processes of the atmosphere being the controlling causes on which depend the agricultural or pastoral pursuits of the inhabitants of extensive tracts of continents.

As the quantity of moisture in the atmosphere increases with the temperature, this element, which is so important for the whole organic creation, must vary with the hours of the day, the seasons of the year, and the differences in latitude and elevation. Our knowledge of the hygrometric relations of the Earth's surface has been very materially augmented of late years by the general application of August's psychrometer, framed in accordance with the views of Dalton and Daniell, for determining the relative quantity of vapor, or the p 333 condition of moisture of the atmosphere, by means of the difference of the 'dew point' and of the temperature of the air. Temperature, atmospheric pressure, and the direction of the wind, are all intimately connected with the vivifying action of atmospheric moisture. This influence is not, however, so much a consequence of the quantity of moisture held in solution in different zones, as of the nature and frequency of the precipitation which moistens the ground, whether in the form of dew, mist, rain, or snow. According to the exposition made by Dove of the law of rotation, and to the general views of this distinguished physicist,* it would appear that, in our northern zone, "the elastic force of the vapor is greatest with a southwest, and least with a northeast wind. On the western side of the windrose this elasticity diminishes, while it increases on the eastern side; on the former side, for instance, the cold, dense, and dry current of air repels the warmer, lighter current containing an abundance of aqueous vapor, while on the eastern side it is the former current which is repulsed by the latter.

The agreeable and fresh verdure which is observed in many trees in districts within the tropics, where, for five or seven months of the yeqar, not a cloud is seen on the vault of heaven, and where no perceptible dew or rain falls, proves that the leaves are capable of extyracting water from the atmosphere by a peculiar vital process of their own, which perhaps is not alone that of producing cold by radiation. The absence of rain in the arid plains of Cumana, Coro, and Ceara in North Brazil, forms a striking contrast to the quanitity of rain which falls in some tropical regions, as, for instance, in the Havana, where it would appear, from the average of six years' observation by Ramong de la Sagra, the mean annual quantity of rain is 109 inches, equal to four or five times that which falls at Paris or at Geneva.*

On the declivity of the Cordilleras, p 334 the quantity of rain, as well as the temperature, diminishes with the increase in the elevation.*

My South American fellow-traveler, Caldas, found that, at Santa Fe de Bogota, at an elevation of almost 8700 feet, it did not exceed 37 inches, being consequently little more than on some parts of the western shore of Europe. Boussingault occasionally observed at Quito that Saussure's hygrometer receded to 26 degrees with a temperature of from 53.6 degrees to 55.4 degrees. Gay-Lussac saw the same hygrometer standing at 25.3 degrees in his great aerostatic ascent in a stratum of air 7034 feet high, and with a temperature of 39.2 degrees. The greatest dryness that has yet been observed on the surface of the globe in the low lands is probably that which Gustav Rose, Ehrenberg, and myself found in Northern Asia, between the valleys of the Irtisch and the Oby. In the Steppe of Platowskaja, after southwest winds had blown for a long time from the interior of the Continent, with a temperature of 74.7 degrees, we found the dew point at 24 degrees. The air contained only 16/100ths of aqueous vapor.*

The accurate observers Kämtz, Bravais, and Martins have raised doubts during the last few years regarding the greater dryness of the mountain air, which appeared to be proved by the hygrometric measurements made by Saussure and myself in the higher regions of the Alps and the Cordilleras. The strata of air at Zurich and on the Faulhorn, which can not be considered as an elevated mountain when compared with non-European elevations, furnished the data employed in the comparisons made by these observers.*

In the tropical region of the Paramos (near the region where snow begins to fall, at an elevation of between 12,000 and 14,000 feet), some species of large flowering myrtle-leaved alpine shrubs are almost constantly bathed in moisture; but this fqact does not actually prove the existence of any great and absolute quantity of aqueous vapor at such an elevation, merely affording p 335 an evidence of the frequency of aqueous precipitation, in like manner as do the frequent mists with which the lovely plateau of Bogota is covered. Mists arise and disappear several times in the course of an hour in such elevations as these, and with a calm state of the atmosphere. These rapid alternations characterize the Paramos and the elevated plains of the chain of the Andes.

'The electricity of the atmosphere', whether considered in the lower or in the upper strata of the clouds, in its silent problematical diurnal course, or in the explosion of the lightning and thunder of the tempest, appears to stand in a manifold relation to all phenomena of the distribution of heat, of the pressure of the atmosphere and its disturbances, of hydrometeoric exhibitions, and probably, also, of the magnetism of the external crust of the earth. It exercises a powerful influence on the whole animal and vegetable world; not merely by meteorological processes, as precipitations of aqueous vapor, and of the acids and ammoniacal compounds to which it gives rise, but also directly as an electric force acting on the nerves, and promoting the circulation of the organic juices. This is not a place in which to renew the discussion that has been started regarding the actual source of atmospheric eletricity when the sky is clear, a phenomenon that has alternately been ascribed to the evaporation of impure fluids impregnated with earths and salts,* to the growth of plants,** or to some other chemical decompositions on the surface of the earth, to the unequal distribution of heat in the strata of the air,*** and, finally, according to Peltier's intelligent researches,**** to the agency of a constant charge of negative electricity in the terrestrial globe.

Limiting itself to results yielded by electrometric observations, such, for instance, as are furnished by the ingenious electro-magnetic apparatus first proposed by Colladon, the physical description of the universe should merely notice the incontestable increase of intensity in the general positive electricity of the atmosphere,* accompanying an increase of altitude and and the absence of trees, its daily variations (which, according to Clark's experiments at Dublin, p 336 take place at more complicated periods than those found by Saussure and myself), and its variations in the different seasons of the year, at different distances from the equator, and in the different relations of continental or oceanic surface.

The electric equilibrium is less frequently disturbed where the aerial ocean rests on a liquid base than where it impends over the land; and it is very striking to observe how, in extensive seas, small insular groups affect the condition of the atmosphere, and occasion the formation of storms. In fogs, and in the commencement of falls of snow, I have seen, in a long series of observations, the previously permanent positive electricity rapidly pass into the negative condition, both on the plains of the colder zones, and in the Paramos of the Cordilleras, at elevations varying from 11,000 to 15,000 feet. The alternate transition was precisly similar to that indicated by the electrometer shortly before and during a storm.*

When the vesicles of vapor have become condensed into clouds, having definite outlines, the electric tension of the external surface will be increased in proportion to the amount of electricity which passes over to it from the separate vesicles of vapor.*

Slate-gray clouds are charged, according to Peltier's experiments at Paris, with negative, and white, red, and orange-colored clouds with positive electricity. Thunder clouds not only envelop the highest summits of the chain of the Andes (I have myself seen the electric effect of lightning on one of the rocky pinnacles which project upward of 15,000 feet above the crater of the volcano of Toluca), but they have also been observed at a vertical height of 26,650 feet over the low p 337 lands in the temperate zone.*

Sometimes, however, the stratum of cloud from which the thunder proceeds sinks to a distance of 5000, or, indeed, only 3000 feet above the plain.

According to Arago's investigations -- the most comprehensive that we possess on this difficult branch of meteorology -- the evolution of light (lightning) is of three kinds -- zigzag, and sharply defined at the edges; in sheets of light, illuminating a whole cloud, which seems to open and refeal the light within it; and in the form of fire-balls.*

The duration of the two first kinds scarcely continues the thousandth part of a second; but the globular lightning moves much more slowly remaining visible for several seconds. Occasionally (as is proved by the recent observations, which have confirmed the description given by Nicholson and Beccaria of this phenomenon), isolated clouds, standing high above the horizon, continue uninterruptedly for some time to emit a luminous radiance from their interior and from their margins, although there is no thunder to be heard, and no indication of a storm; in some cases even hail-stones, drops of rain, and flakes of snow have been seen to fall in a luminous condition, when the phenomenon was not preceded by thunder. In the geographical distribution of storms, the Peruvian coast, which is not visited by thunder or lightning, presents the most striking contrast to the rest of the tropical zone, in which, at certain seasons of the year, thunder-storms occur almost daily, about four or five hours after the sun has reached the meridian. According to the abundant evidence collected by Arago* from the testiimony of navigators (Scoresby, Parry, Ross, and Franklin), there can be no doubt that, in general, electric explosions are extremely rare in high northern regions (between 70 degrees and 75 degrees latitude).

'The meteorological portion' of the descriptive history of nature which we are now concluding shows that the processes of the absorption of light, the liberation of heat, and the variations in the elastic and electric tension, and in the hygrometric condition of the vast aerial ocean, are all so intimately connected together, that each individual meteorological process is modified by the action of all the others. The complicated p 338 nature of these disturbing causes (which involuntarily remind us of those which the near and especially the smallest cosmical bodies, the satellites, comets, and shooting stars, are subjected to in their course) increases the difficulty of giving a full explanation of these involved meteorological phenomena, and likewise limits, or wholly precludes, the possibility of that predetermination of atmospheric changes which would be so important for horticulture, agriculture, and navigation, no less than for the comfort and enjoyment of life. Those who place the value of meteorology in this problematic species of prediction rather than in the knowledge of the phenomena themselves, are firmly convinced that this branch of science, on account of which so many expeditions to distant mountainous regions have been undertaken, has not made any very considerable progress for centuries past. The confidence which they refuse to the physicist they yield to changes of the moon, and to certain days marked in the calendar by the superstition of a by-gone age.

"Great local deviations from the distribution of the mean temperature are of rare occurrence, the variations being in general uniformly distributed over extensive tracts of land. the deviation, after attaining its maximum at a certain point, gradually decreases to its limits; when these are passed, however, decided deviations are observed in the 'opposite direction'. Similar relations of weather extend more frequently from south to north than from west to east. At the close of the year 1829 (when I had just completed my Siberian journey), the maximum of cold was at Berlin, while North America enjoyed an unusually high temperature. It is an entirely arbitrary assumption to believe that a hot summer succeeds a severe winter, and that a cool summer is preceded by a mild winter." Opposite relations of weather in contiguous countries, or in two corn-growing continents, give rise to a beneficient equalization in the prices of the products of the vine, and of agricultural and horticultural cultivation. It has been justy remarked, that it is the barometer alone which indicates to us the changes that occur in the pressure of the air throughout all the aerial strata from the place of observation to the extremest confines of the atmosphere, while* the thermometer and psychrometer only acquaint us with all the variations occurring in the local heat and moisture of the lower strata of p 339 air in contact with the ground.

The simultaneous thermic and hygrometric modifications of the upper regions of the air can only be learned (when direct observations on mountain stations or aerostatic ascents are impracticable) from hypothetical combinations, by making the barometer serve both as a thermometer and an hygrometer. Important changes of weather are not owing to merely local causes, situated at the place of observation, but are the consequence of a disturbance in the equilibrium of the aerial currents at a great distance from the surface of the Earth, in the higher strata of the atmosphere, bringing cold or warm, dry or moist air, rendering the sky cloudy or serene, and converting the accumulated masses of clouds into light feathery 'cirri'. As, therefore, the inaccessibility of the phenomenon is added to the manifold nature and complication of the disturbances, it has always appeared to me that meteorology must first seek its foundation and progress in the torrid zone, where the variations of the atmospheric pressure, the course of hydro-meteors, and the phenomena of electric explosion, are all of periodic occurrence.

As we have now passed in review the whole sphere of inorganic terrestrial life, and have briefly considered our planet with reference to its form, its internal heat, its electro-magnetic tension, its phenomena of polar light, the volcanic reaction of its interior on its variously composed solid crust, and, lastly, the phenomena of its two-fold envelopes -- the aerial and liquid ocean -- we might, in accordance with the older method of treating physical geography, consider that we had completed our descriptive history of the globe. But the nobler aim I have proposed to myself, of raising the contemplation of nature to a more elevated point of view, would be defeated, and this delineation of nature would appear to lose its most attractive charm, if it did not also include the sphere of organic life in the many stages of its typical development. The idea of vitality is so intimatey associated with the idea of the existence of the active, ever-blending natural forces which animate the terrestrial sphere, that the creation of plants and animals is ascribed in the most ancient mythical representations of many nations to these forces, while the condition of the surface of our planet, before it was animated by vital forms, is regarded as coeval with the epoch of a chaotic conflict of the struggling elements. But the empirical domain of objective contemplation, and the delineation of our planet in its present condition, do not include a consideration p 340 of the mysterious and insoluble problems of origin and existence.

A cosmical history of the universe, resting upon facts as its basis, has, from the nature and limitations of its sphere, necessarily no connection with the obscure domain embraced by a 'history of organisms',* if we understand the word 'history' in its broadest sense.

It must, however, be remembered, that the inorganic crust of the Earth contains within it the same elements that enter into the structure of animal and vegetable organs. A physical cosmography would therefore be incomplete p 341 if it were to omit a consideration of these forces, and of the substances which enter into solid and fluid combinations in organic tissues, under conditiions which, from our ignorance of their actual nature, we designate by the vague term of 'vital forces', and group into various systems in accordance with more or less perfectly conceived analogies. The natural tendency of the human mind involuntarily prompts us to follow the physical phenomena of the Earth, through all their varied series, until we reach the final stage of the morphological evolution of vegetable forms, and the self-determining powers of motion in animal organisms. And it is by these links that 'the geography of organic beings -- of plants and animals' -- is connected with the delineation of the inorganic phenomena of our terrestrial globe.

Without entering on the difficult question of 'spontaneous motion', or, in other words, on the difference between vegetable and animal life, we would remark, that if nature had endowed us with microscopic powers of vision, and the integuments of plants had been rendered perfectly transparent to our eyes, the vegetable world would present a very different aspect from the apparent immobility and repose in which it is now manifested to our senses. The interior portion of the cellular structure of their organs is incessantly animated by the most varied currents, either rotating, ascending and descending, remifying, and ever changing their direction, as manifested in the motion of the granular mucus of marine plants (Naiades, Characeae, Hydrocharidae), and in the hairs of phanerogamic land plants; in the molecular motion first discovered by the illustrious botanist Robert Brown, and which may be traced in the ultimate portions of every molecule of matter, even when separated from the organ; in the gyratory currents of the globules of cambium ('cyclosis') circulating in their peculiar vessels; and, finally, in the singularly articulated self-unrolling filamentous vessels in the antheridia of the chara, and in the reproductive organs of liverworts and algae, in the structural conditions of which Meyen, unhappily too early lost to science, believed that he recognized an analogy with the spermatozoa of the animal kingdom.*

If to these p 342 manifold currents and gyratory movements we add the phenomena of endosmosis, nutrition, and growth, we shall have some idea of those forces which are ever active amid the apparent repose of vegetable life.

Since I attempted in a former work, 'Ansichten der Natur' (Views of Nature), to delineate the universal diffusion of life over the whole surface of the Earth, in the distribution of organic forms, both with respect to elevation and depth, our knowledge of this branch of science has been most remarkably increased by Ehrenberg's brilliant discovery "on microscopic life in the ocean, and in the ice of the polar regions" -- a discovery based, not on deductive conclusions, but on direct observation. The sphere of vitality, we might almost say, the horizon of life, has been expanded before our eyes. "Not only in the polar regions is there an uninterrupted development of active microscopic life, where larger animals can no longer exist, but we find that the microscopic animals collected in the Antarctic expedition of Captain James Ross exhibit a remarkable abundance of unknown and often most beautiful forms. Even in the residuum obtained from the melted ice, swimming about in round fragments in the latitude of 70 degrees 10', there were found upward of fifty species of silicious-shelled Polygastria and Coscinodiscae with their green ovaries, and therefore living and able to resist the extreme severity of the cold. In the Gulf of Erebus, sixty-eight silicious-shelled Polygastria and Phytolitharia, and only one calcareous-shelled Polythalamia, were brought up by lead sunk to a depth of from 1242 to 1620 feet."

The greater number of the oceanic microscopic forms hitherto discovered have been silicious-shelled, although the analysis of sea water does not yield silica as the main constituent, and it can only be imagined to exist in it in a state of suspension. It is not only at particular points in inland seas, or in the vicinity of the land, that the ocean is densely inhabited by living atoms, invisible to the naked eye, but samples of p 343 water taken up by Schayer on his return from Van Diemen's Land (south of the Cape of Good Hope, in 57 degrees latitude, and under the tropics in the Atlantic) show that the ocean in its ordinary condition, without any apparent discoloration, contains numerous microscopic moving organisms, which bear no resemblance to the swimming fragmentary silicious filaments of the genus Chaetoceros, similar to the Oscillatoriae so common in our fresh waters. Some few Polygastria, which have been found mixed with sand and excrements of penguins in Cockburn Island, appear to be spread over the whole earth, while others seem to be peculiar to the polar regions.*

We thus find from the most recent observations that animal life predominates amid the eternal night of the depths of ocean, while vegetable life, which is so dependent on the periodic action of the solar rays, is most prevalent on continents. The mass of vegetation on the Earth very far exceeds that of animal organisms; for what is the volume of all the large living Cetacea and Pachydermata when compared with the thickly-crosded colossal trunks of trees, of from eight to twelve feet in diameter, which fill the vast forests covering the tropical region of South America, between the Orinoco, the Amazon, and the Rio de Madeira? And although the character of different portions of the earth depends on the combination of external phenomena, as the outlines of mountains -- the physiognomy of plants and animals -- the azure of the sky -- the forms of the clouds -- and the transparency of the atmosphere -- it must still be admitted that the vegetable mantle with which the earth is decked constitutes the main feature of the picture. Animal forms are inferior in mass, and their powers of motion often withdraw them from our sight. The p 344 vegetable kingdom, on the contrary, acts upon our imagination by its continued presence and by the magnitude of its forms; for the size of a tree indicates its age, and here alone age is associated with the expression of a constantly renewed vigor.*

In the animal kingdom (and this knowledge is also the result of Ehrenberg's discoveries), the form which we term microscopic occupy the largest space, in consequence of their rapid propagation.*

The minutest of the Infusoria, the Monadidae, have a diameter which does not exceed 1/3000th of a line, and yet these silicious-shelled organisms form in humid districts subterranean strata of many fathoms in depth.

The strong and beneficial influence exercised on the feelings of mankind by the consideration of the diffusion of life, throughout the realms of nature is common to every zone, but the impression thus produced is most powerful in the equatorial regions, in the land of palms, bamboos, and arborescent ferns, where the ground rises from the shore of seas rich in mollusca and corals to the limits of perpetual snow. The local distribution of plants embraces almost all heights and all depths. Organic forms not only descend into the interior of the earth, where the industry of the miner has laid open extensive excavations and sprung deep shafts, but I have also found snow-white stalactiitic columns encircled by the delicate web of an Usnea, in caves where meteoric water could alone penetrate through fissures. Podurellae penetrate into the icy crevices of the glaciers on Mount Rosa, the Grindelwald, and the Upper Aar; the Chionaea nivalis (formerly known as Protococcus), exist in the polar snow as well as in that of our high mountains. The redness assumed by the snow after lying on the ground for soome time was known to Aristotle, and was probably observed by him on the mountains of Macedonia.*

p 345 While, on the loftiest summits of the Alps, only Lecideae, Parmeliae, and Umbilicariae cast their colored but scanty covering over the rocks, exposed by the melted snow, beautiful phanerogamic plants, as the Culcitium rufescens, Sida pinchinchensis, and Saxifraga Boussingaulti, are still found to flourish in the tropical region of the chain of the Andes, at an elevation of more than 15,000 feet. Thermal springs contain small insects (Hydroporus thermalis), Gallionellae, Oscillatoria and Confervae, while their waters bathe the root-fibers of phanerogamic plants. As air and water are aniimated at different temperatures by the presence of vital organisms, so likewise is the interior of the different portions of animal bodies. Animalcules have been found in the blood of the frog and the salmon; according to Nordmann, the fluids in the eyes of fishes are often filled with a worm that lives by suction (Diplostomum), while in the gills of the bleak the same observer has discovered a remarkable double aniimalcule (Diplozoon paradoxum), having a cross-shaped form with two heads and two caudal extremities.

Although the existence of meteoric Infusoria is more than doubtful, it can not be denied that, in the same manner as the pollen of the flowers of the pine is observed every year to fall from the atmosphere, minute infusorial animalcules may likewise be retained for a time in the strata of the air, after having been passively borne up by currents of aqueous vapor.*

This circumstance merits serious attention in reconsidering the old discussion respecting 'spontaneous generation',* and the p 346 more so, as Ehrenberg, as I have already remarked, has discovered that the nebulous dust or sand which mariners often encounter in the vicinity of the Cape Verd Islands, and even at a distance of 380 geographical miles from the African shore, contains the remains of eighteen species of silicious-shelled polygastric animalcules.

Vital organisms, whose relations in space are comprised under the head of the geography of plants and animals, may be considered either according to the difference and relative numbers of the types (their arrangement into genera and species), or according to the number of individuals of each species on a given area. In the mode of life of plants as in that of animals, an important difference is noticed; they either exist in an isolated state, or live in a social condition. Those species of plants which I have termed 'social'* uniformly cover vast extents of land.

Among these we may reckon many of the marine Algae -- Cladoniae and mosses, which extend over the desert steppes of Northern Asia -- grasses, and cacti growing p 347 together like the pipes of an organ -- Avicennim and mangroves in the tropics -- and forests of Coniferae and of birches in the plains of the Baltic and in Siberia. This mode of geographical distribution determines, together with the individual form of the vegetable world, the size and type of leaves and flowers, in fact, the principal physiognomy of the district,* its characteracter being but little, if at all, influenced by the ever-moving forms of animal life, which, by their beauty and diversity, so powerfully affect the feelings of man, whether by exciting the sensations of admiration or horror.

Agricultural nations increase artificially the predominance of social plants, and thus augment, in many parts of the temperate and northern zones, the natural aspect of uniformity; and while their labors tend to the extirpation of some wild plants, they likewise lead to the cultivation of others, which follow the colonist in his most distant migration. The luxuriant zone of the tropics offers the strongest resistance to these changes in the natural distribution of vegetable forms.

Observers who in short periods of time have passed over vast tracts of land, and ascended lofty mountains, in which climates were ranged, as it were in strata one above another, must have been early impressed by the regularity with which vegetable forms are distributed. The results yielded by their observations furnished the rough materials for a science, to which no name had as yet been given. The same zones of regions of vegetation which, in the sixteenth century, Cardinal Bembo, when a youth,*described on the declivity of Aetna, were observed on Mount Ararat by Tournefort.

He ingeniously compared the Alpine flora with the flora of plains situated in different latitudes, and was the first to observe the influence exercised in mountainous regions, on the distribution of plants by the elevation of the ground above the level of the sea, and by the distance from the poles in flat countries. Menzel, in an inedited work on the flora of Japan, accidentally made use of the term 'geography of plants'; and the same expression occurs in the fanciful but graceful work of Bernardin de St. Pierre, 'Etudes de la Nature'. A scientific treatment of the subject began, however, only when the geography of plants was intimately associated with the study of the distribution p 348 of heat over the surface of the earth, and when the arrangement of vegetable forms in natural families admitted of a numerical estimate being made of the different forms which increase of decrease as we recede from the equator toward the poles, and of the relations in which, in diffrent parts of the earth, each family stood with reference to the whole mass of phanerogamic indigenous plants of the same region. I consider it a happy circumstance that, at the time during which I devoted my attention almost exclusively to botanical pursuits, I was led by the aspect of the grand and strongly characterized features of tropical scenery to direct my investigations toward these subjects.

The study of the geographical distribution of animals, regarding which Buffon first advanced general, and, in most instances, very correct views, has been considerably aided in its advance by the progress made in modern times in the geography of plants. The curves of the isothermal lines, and more especially those of the isochimenal lines, correspond with the limits which are seldom passed by certain species of plants, and of animals which do not wander far from their fixed habitation either with respect to elevation or latitude.*

The p 349 elk, for instance, lives in the Scandinavian peninsula, almost ten degrees further north than in the interior of Siberia, where the line of equal winter temperature is so remarkably concave. Plants migrate in the germ; and, in the case of many species, the seeds are furnished with organs adapting them to be conveyed to a distace through the air. When once they have taken root, they become dependent on the soil and on the strata of air surrounding them. Animals, on the contrary, can at pleasure migrate from the equator toward the poles; and this they can more especially doo where the isothermal lines are much inflected, and where hot summers succeed a great degree of winter cold. The royal tiger, which in no respect differs from the Bengal species, penetrates every summer into p 350 the north of Asia as far as the latitudes of Berlin and Hamburg, a fact of which Ehrenberg and myself have spoken in other works.*

The grouping or association of diffrent vegetable species, to which we are accustomed to apply the term 'Floras', do not appear to me, from what I have observed in different portions of the earth's surface, to manifest such a predominance of individual families as to justify us in marking the geographical distinctions between the regions of the Umbellatae, of the Solidaginae, of the Labiatae, or the Scitamineae. With reference to this subject, my views differ from those of several of my friends, who rank among the most distinguished of the botanists of Germany. The character of the floras of the elevated plateaux of Mexico, New Granada, and Quito, of European Russia, and of Northern Asia, consists, in my opinion, not so much in the relatively larger number of the species presented by one or two natural families, as in the more complicated relations of the coexistence of many families, and in the relative numerical value of their species. The Gramineae and the Cyperaceae undoubtedly predominate in meadow lands and stppes, as do Coniferae, Cupuliferae, and Betulineae in our northern woods; but this predominance of certain forms is only apparent, and owing to the aspect imparted by the social plants. The north of Europe, and that portion of Siberia which is situated to the north of the Altai Mountains, have no greater right to the appellation of a region of Gramineae and Coniferae than have the boundless llanos between the Orinoco and the mountain chain of Caraccas, or the pine forests of Mexico. It is the coexistence of forms which may partially replace each other, and their relative numbers and association, which give rise either to the general impression of luxuriance and diversity, or of poverty and uniformity in the contemplation of the vegetable world.

In this fragmentary sketch of the phenomena of organization, I have ascended from the simplest cellI -- the first manifestation of life -- progressively to higher structures. "The p 351 association of mucous granules constitutes a definitely-formed cytoblase, around which a vesicular membrane forms ia closed well," this cell being either produced from another pre-existing cell,** or being due to a cellular formation, which, as in the case of the fermentation-fungus, is concealed in the obscurity of some unknown chemical process.***

But in a work like the present we can venture on no more than an allusion to the mysteries that involve the question of modes of origin; the geography of animal and vegetable organisms must limit itself to the consideration of germs already developed, of their haabitation and transplantation, either by voluntary or involuntary migrations, their numerical relation, and their distribution over the surface of the earth.

The general picture of nature which I have endeavored to delineate would be incomplete if I did not venture to trace a few of the most marked features of the human race, considered with reference to physical gradations -- to the geographical distribution of contemporaneous types -- to the influence exercised upon man by the forces of nature, and the reciprocal, although weaker action which he in his turn exercises on these natural forces. Dependent, although in a lesser degree than plants and animals, on the soil, and on the meteorological processes of the atmosphere with which he is surroounded -- escaping more readily from the control of natural forces, by activity of mind and the advance of intellectual cultivation, no less than by his wonderful capacity of adapting himself to all climates -- man every where becomes most essentially associated with terrestrial life. It is by these relations that the obscure and much-contested problem of the possibility of one common descent enters into the sphere embraced by a general physical cosmography. The investigation of this problem will impart a nobler, and, if I may so express myself, more purely human interest to the closing pages of this section of my work.

The vast domain of language, in whose varied structure we see mysteriously reflected the destinies of nations, is most intimately associated with the affinity of races; and what even slight differences of races may effect is strikingly manifested in the history of the Hellenic nations in the zenith of their intellectual cultivation. The most important questions of the civilization of mankind are connected with the ideas of races, p 352 community of language, and adherence to one original direction of the intellectual and moral faculties.

As long as attention was directed solely to the extremes in varieties of color and of form, and to the vividness of the first impression of the senses, the observer was naturally disposed to regard races rather as originally different species than as mere varieties. The permanence of certain types* in the midst of the most hostile influences, especially of climate, appeared to favor such a view, notwithstanding the shortness of the interval of time from which the historical evidence was derived.

In my opinion, however, more powerful reasons can be advanced in support of the theory of the unity of the human race, as, for instance, in the many intermediate gradations* in the color of the skin and in the form of the skull, which have been made known to us in recent times by the rapid progress of geographical knowledge -- the analogies presented by the varieties in the species of many wild and domesticated animals -- and the more correct observations collected regarding the limits of fecundity in hybrids.**

The greater number of the contrasts which were formerly supposed to exist, have disappeared before the laborious researches of Tiedemann on the brain of negroes and of Europeans, and the anatomical investigations p 353 of Vrolik and Weber on the form of the pelvis. On comparing the dark-colored African nations, on whose physical history the admirable work of Prichard has thrown so much light, with the races inhabiting the islands of the South-Indian and West-Australian archipelago, and with the Papuas and Alfourous (Haroforas, Endamenes), we see that a black skin, woolly hair, and a negro-like cast of countenance are not necessarily connected together.*

So long as only a small portion of the earth was known to the Western nations, partial views necessarily predominated, and tropical heat and a black skin consequently appeared inseparable. "The Ethiopians," said the ancient tragic poet Theodectes of Phaselis,* "are colored by the near sun-god in his course with a sooty luster, and their hair is dried and crisped with the heat of his rays."

The campaigns of Alexander, which gave rise to so many new ideas regarding physical geography, likewise first excited a discussion on the problematical influence of climate on races. "Families of animals and plants," writes one of the greatest anatomists of the day, Johannes Muller, in his noble and comprehensive work, 'Physiologie des Menschen', "undergo, within certain limitations peculiar to the different races and species, various modifications in their distribution over the surface of the earth, propagating these variations as organic types of species.*

The different races of mankind are forms of one sole species, by the union of two of whose members descendants are propagated. They are not different species of a genus, since in that case their hybrid descendants would remain unfruitful. But whether the human races have descended from several primitive races of men, or from one alone, is a question that can not be determined from experience."*

Geographical investigations regarding the ancient 'seat', the so-called 'cradle of the human race', are not devoid of a mythical p 355 character. "We do not know," says Wilhelm von Humboldt, in an unpublished work 'On the Varieties of Languages and Nations', "either from history or from authentic tradition, any period of time in which the human race has not been divided into social groups. Whether the gregarious condition was original, or of subsequent occurrence, we have no historic evidence to show. The separate mythical relations found to exist independently of one another in different parts of the earth, appear to refute the first hypothesis, and concur in ascribing the generation of the whole human race to the union of one pair. The general prevalence of this myth has cause it to be regarded as a traditionary record transmitted from the primitive man to his descendants. But this very circumstance seems rather to prove that it has no historical foundation, but has simply arisen from an identity in the mode of intellectual conception, which has every where led man to adopt the same conclusion regarding identical phenomena; in the same manner as many myths have doubtlessly arisen, not from any historical connection existing between them, but rather from an identity in human thought and imagination. Another evidence in favor of the purely mythical nature of this belief is afforded by the fact that the first origin of mankind -- a phenomenon which is wholly beyond the sphere of experience -- is explained in perfect conformity with existing views, being considered on the principle of the colonization of some desert island or remote mountainous valley at a period when mankind had already existed for thousands of years. It is in vain that we direct our thoughts to the solution of the great problem of the first origin, since man is too intimately associated with his own race and with the relations of time to conceive of the existence of an individual independently of a preceding generation and age. A solution of those difficult questions, which can not be determined by inductive reasoning or by experience -- whether the belief in this presumed traditional condition be actually based on historical evidence, or whether mankind inhabited the earth in gregarious associations from the origin of the race -- can not, therefore, be determined from philological data, and yet its elucidation ought not to be sought from other sources."

The distribution of mankind is therefore only a distribution into 'varieties', which are commonly designated by the somewhat indefinite term 'races'. As in the vegetable kingdom, and in the natural history of birds and fishes, a classification into many small families is based on a surer foundation than p 356 where large sections are separated into a few but large divisions; so it also appears to me, that in the determination of races a preference should be given to the establishment of small families of nations. Whether we adopt the old classification of my master, Blumenbach, and admit 'five' races (the Caucasian, Mongolian, American, Ethiopian, and Malayan), or that of Prichard, into 'seven races'* (the Iranian, Turanian, American, Hottentots and Bushmen, Negroes, Papuas, and Alfourons), we fail to recognize any typical sharpness of definition, or any general or well-established principle in the division of these groups.

The extremes of form and color are certainly separated, but without regard to the races, which can not be included in any of these classes, and which have been alternately termed Scythian and Allophyllic. Iranian is certainly a less objectionable term for the European nations than Caucasian; but it may be maintained generally that geographical denominations are very vague when used to express the points of departure of races, more especially where the country which has given its name to the race, as, for instance, Turan (Mawerannahr), has been inhabited at different periods* by Indo-Germanic and Finnish, and not by Mongolian tribes.

p 357 Languages, as intellectual creations of man, and as closely interwoven with the development of mind, are, independently of the 'national' form which they exhibit, of the greatest importance in the recognition of similarities or differences in races. This importance is especially owing to the clew which a community of descent affords in treading that mysterious labyrinth in which the connection of physical powers and intellectual forces manifests itself in a thousand different forms. The brilliant progress made within the last half century, in Germany, in philosophical philology, has greatly facilitated our investigations into the 'national' character* of languages and the influence exercised by descent.

But here, as in all domains of ideal speculation, the dangers of deception are closely linked to the rich and certain profit to be derived.

Positive ethnographical studies, based on a thorough knowledge of history, teach us that much caution should be applied in entering into these comparisons of nations, and of the languages employed by them at certain epochs. Subjection, long association, the influence of a foreign religion, the blending of races, even when only including a small number of the more influential and cultivated of the immigrating tribes, have produced, in both continents, similarly recurring phenomena; as, for instance, in introducing totally different families of languages among one and the same race, and idioms, having one common root, among nations of the most different origin. Great Asiatic conquerors have exercised the most powerful influence on phenomena of this kind.

But language is a part and parcel of the history of the development of mind; and however happily the human intellect, under the most dissimilar physical conditions, may unfettered pursue a self-chosen track, and strive to free itself from the dominion of terrestrial influences, this emancipation is never perfect. There ever remains, in the natural capacities of the mind, a trace of something that has been derived from the influences of race or of climate, whether they be associated with a land gladdened by cloudless azure skies, or with the vapory atmosphere of an insular region. As, therefore, richness and grace of language are unfolded from the most luxuriant p 358 depths of thought, we have been unwilling wholly to disregard the bond which so closely links together the physical world with the sphere of intellect and of the feelings by depriving this general picture of nature of those brighter lights and tints which may be borrowed from considerations, however slightly indicated, of the relations existing between races and languages.

While we maintain the unity of the human species, we at the same time repel the depressing assumption of superior and inferior races of men.*

There are nations more susceptible of cultivation, more highly civilized, more enobled by mental cultivation than others, but none in themselves nobler than others. All are in like degree designed for freedom; a freedom which, in the ruder conditions of society, belongs only to the individual, but which, in social states enjoying political institutions, appertains as a right to the whole body of the community. "If we would indicate an idea which, throughout the whole course of history, has ever more and more widely extended its empire, or which, more than any other, testifies to the much-contested and still more decidedly misunderstood perfectibility of the whole human race, it is that of establishing our common humanity -- of striving to remove the barriers which prejudice and limited views of every kind have erected among men, and to treat all mankind, without reference to religion, nation, or color, as one fraternity, one great community, fitted for the attainment of one object, the unrestrained development of the physical powers. This is the ultimate and highest aim of society, identical with the direction implanted by nature in the mind of man toward the indefinite extension of his existence. He regards the earth in all its limits, and the heavens as far as his eye can scan their bright and starry depths, as inwardly his own, given to him as the objects of his contemplation, and as a field for the development of his energies. Even the child longs to pass the hills or the seas which inclose his narrow home; yet, when his eager steps have borne him beyond those limits, he pines, like the plant, for his native soil; and it is by this touching and beautiful attribute of man -- this longing for that which is unknown, and this fond remembrance of that which is lost -- that he is spared from an exclusive attachment to the present. p 359 Thus deeply rooted in the innermost nature of man, and even enjoined upon him by his highest tendencies, the recognition of the bond of humanity becomes one of the noblest leading principles in the history of mankind."*

With these words, which draw their charm from the depths of feeling, let a brother be permitted to close this general description of the natural phenomena of the universe. From the remotest nebulae and from the revolving double stars, we have descended to the minutest organisms of animal creation, whether manifested in the depths of ocean or on the surface of our globe, and to the delicate vegetable germs which clothe the naked declivity of the ice-crowned mountain summit; and here we have been able to arrange these phenomena according to partially known laws; but other laws of a more mysterious nature rule the higher spheres of the organic world, in which is comprised the human species in all its varied conformation, its creative intellectual power, and the languages to which it has given existence. A physical delineation of nature terminates at the point where the sphere of intellect begins, and a new world of mind is opened to our view. It marks the limit, but does not pass it.

p 360 is blank

p 361

ADDITIONAL NOTES

TO THE PRESENT EDITION. MARCH, 1849.

__________

GIGANTIC BIRDS OF NEW ZEALAND. -- Vol. i., p. 287. An extensive and highly interesting collection of bones, referrible to several species of the 'Moa' (Dinornis of Owen), and to three or four other genera of birds, formed by Mr. Walter Mantell, of Wellington, New Zealand, has recently arrived in England, and is now deposited in the British Museum. This series consists of between 700 and 800 speciments, belonging to different parts of the skeletons of many individuals of various sizes and ages. Some of the largest vertebrae, tibiae, and femora equal in magnitude the most gigantic previously known, while others are not larger than the corresponding bones of the living apteryx. Among these relics are the 'skulls' and 'mandibles' of two genera, the 'Dinornis' and 'Palapteryx'; and of an extinct genus, 'Notornis', allied to the 'Rallidae'; and the mandibles of a species of 'Nestor', a genus of nocturnal owl-like parrots, of which only two living species are known.*

These osseous remains are in a very different state of preservation from any previously received from New Zealand; they are light and porous, and of a light fawn-color; the most delicate processes are entire, and the articulating surfaces smooth and uninjured; 'fragments of egg-shells', and even the bony rings of the trachea and air tubes, are preserved'.

The bones were dug up by Mr. Walter Mantell from a bed of marly sand, containing magnetic iron, crystals of hornblende and augite, and the detritus of augitic rocks and earthy volcanic tuff. The sand had filled up all the cavities and cancelli, but was in no instance consolidated or aggregated together; it was, therefore, easily removed by a soft brush, and the bones perfectly cleared without injury.

The spot whence these precious relics of the colossal birds that once inhabited the islands of New Zealand were obtained, is a flat tract of land, near the embouchure of a river, named Waingongoro, not far from Wanganui, which has its rise in the volcanic regions of Mount Egmont. The natives affirm that this level tract was one of the places first dwelt upon by their remote ancestors; and this tradition is corroborated by the existence of numerous heaps and pits of ashes and charred bones indicating ancient fires, long burning on the same spot. In these fire-heaps Mr. Mantell found burned bones of 'men, moas', and 'dogs'.

The fragments of egg-shells, imbedded in the ossiferous deposits, had escaped the notice of all previous naturalists. They are, unfortunately, very small portions, the largest being only four inches long, but they afford a chord by which to estimate the size of the original. Mr. Mantell observes that the egg of the Moa must have been so large that a hat would form a good egg-cup for it. These relics evidently belong to two or more species, perhaps genera. In some examples the external p 362 surface is smooth; in others it is marked with short intercepted linear grooves, resembling the eggs of some of the Struthiouidae, but distinct from all known recent types. In this valuable collection only one bone of a mammal has been detected, namely, 'the femur of a dog'.

An interesting memoir on the probable geological position and age of the ornithic bone deposits of New Zealand, by Dr. Mantell, based on the observations of his enterprising son, it published in the Quarterly Journal of the Geological Society of London (1848). It appears that in many instances the bones are imbedded in sand and clay, which lie beneath a thick deposit of volcanic detritus, and rest on an argillaceous stratum abounding in marine shells. The specimens found in the rivers and streams have been washed out of their banks by the currents which now flow through channels from ten to thirty feet deep, formed in the more ancient alluvial soil. Dr. Mantell concludes that the islands of New Zealand were densely peopled at a period geologically recent, though historically remote, by tribes of gigantic brevi-pennate birds allied to the ostrich tribe, all, or almost all, of species and genera now extinct; and that, subsequently to the formation of the most ancient ornithic deposit, the sea-coast has been elevated from fifty to one hundred feet above its original level; hence the terraces of shingle and loam which now skirt the maritime districts. The existing rivers and mountain torrents flow in deep gulleys which they have eroded in the course of centuries in these pleistocene strata, in like manner as the river courses of Auvergne, in Central France, are excavated in the mammiferous tertiary deposits of that country. The last of the gigantic birds were probably exterminated, like the dodo, by human agency: some small species allied to the apteryx may possibly be met with in the unexplored parts of the middle island.

THE DODO. -- A most valuable and highly interesting history of the dodo and its kindred* has recently appeared in which the history, affinities, and osteology of the 'Dodo, Solitaire', and other extinct birds of the islands Mauritius, Rodriguez, and Bourbon are admirably elucidated by H. G. Strickland (of Oxford), and Dr. G. A. Melville.

The historical part is by the former, the osteological and physiological portion by the latter eminent anatomist. We would earnestly recommend the reader interested in the most perfect history that has ever appeared, of the extinction of a race of large animals, of which thousands existed but three centuries ago, to refer to the original work. We have only space enough to state that the authors have proved, upon the most incontrovertible evidence, that the dodo was neither a vulture, ostrich, nor galline, as previously anatomists supposed, but a 'frugiverous pigeon'.

This section from pp 363-379 of:

COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt

Translated by E C Otte

from the 1858 Harper & Brothers edition of Cosmos, volume 1 --------------------------------------------------

p 363 INDEX TO VOL. I. -------------------

ABICH, Hermana, structural relations of volcanic rocks, 234.

Acosta, Joseph de, Historia Natural de las Indias, 66, 193.

Adams, Mr., planet Neptune. See note by Translator, 90, 91.

Aegos Potamos, on the aerolite of, 117, 122.

Aelian on Mount Aetna, 227.

Aerolites (shooting stars, meteors, meteoric stones, fire-balls, etc), general description of, 111-137; physical character, 112-123; dates of remarkable falls, 114, 115; their planetary velocity, 116-120; ideas of the ancients on, 115, 116; November and August periodic falls of shooting stars, 118-120, 124-126; their direction from one point in the heavens, 120; altitude, 120; orbit, 127; Chinese notices of, 128; media of communication with other planetary bodies, 136; their essential difference from comets, 137; specific weights, 116, 117; large meteoric stones on record, 117; chemical elements, 117, 129-131; crust, 129, 130; deaths occasioned by, 135.

Aeschylus, "Prometheus Delivered," 115.

Aetna, Mount, its elevation, 28, 229; supposed extinction by the ancients, 227; its eruptions from lateral fissures, 229; similarity of its zones of vegetation to those of Ararat, 347.

Agassiz, Researches on Fossil Fishes, 46, 273-277.

Alexander, influence of his campaigns on physical science, 353.

Alps, the, elevation of, 28, 29.

Amber, researches on its vegetable origin, 284; Goppert on the amber-tree of the ancient world (Pinites succifer), 283.

Ampere, Andre Marie, 58, 193, 236.

Anaxagoras on aerolites, 122; on the surrounding ether, 134.

Andes, the, their altitude, etc. See Cordilleras.

Anghiera, Peter Martyr de, remarked that the palmeta and pineta were found associated together, 282, 283; first recognized (1510) that the limit of perpetual snow continues to ascend as we approach the equator, 329.

Animal life, its universality, 342-345; as viewed with microscopic powers of vision, 341-346; rapid propagation and tenacity of life in animalcules, 344-346; geography of, 341-346.

Anning, Miss Mary, discovery of the ink bag of the sepia, and of coprolites of fish, in the lias of Lyme Regis, 271, 272.

Austed's, D. R., "Ancient World." See notes by Translator, 271, 272, 274, 281, 287.

Aplan, Peter, on comets, 101.

Apollonius Myndius, described the paths of comets, 103.

Arago, his ocular micrometer, 39; chromatic polarization, 52; optical considerations, 85; on comets, 99-106; polarization experiments on the light of comets, 105; aerolites, 114; on the November fall of meteors, 124; zodiacal light, 143; motion of the solar system, 146, 147; on the increase of heat at increasing depths, 173, 174; magnetism of rotation, 179, 180; horary observations of declination at Paris compared with simultaneous perturbations at Kasan, 191; discovery of the influence of magnetic storms on the course of the needle, 194, 195; on south polar bands, 198; on terrestrial light, 202; phenomenon of supplementary rainbows, 220; observed the deepest Artesian wells to be the warmest, 223; explanation of the absence of a refrigeration of temperature in the lower strata of the Mediterranean, 303; observations on the mean annual quantity of rain in Paris, 333; his investigations on the evolution of lightning, 337.

Argelander on the comet of 1811, 109; on the motion of the solar system, 146, 149; on the light of the Aurora, 195, 196.

Aristarchus of Samos, the pioneer of the Copernican system, 65.

Aristotle, 65; his definition of Cosmos, 69; use of the term history, 75; on comets, 103, 104; on the Ligyan field of stones, 115; aerolites, 122; on the stone of Aegos Potamos, 135; aware that noises sometimes existed without earthquakes, 209; his account of the upheavals of islands of eruption, 241; "spontaneous motion," 341; noticed the redness assumed by long fallen snow, 344.

Artesian wells, temperature of, 174, 223.

Astronomy, results of, 38-40; phenomena of physical astronomy, 43, 44.

Atmosphere, the general description of, 311, 316; its composition and admixture, 312; variation of pressure, 313-317; climatic distribution of heat, 313, 317-328; distribution of humidity, 313, 328, 334; electric condition, 314, 335-338.

p 363 August, his psychometer, 332.

Augustine, St., his views on spontaneous generation, 345, 346.

Aurora Borealis, general description of 193-202; origin and course, 195, 196; altitude, 199; brilliancy coincident with the fall of shooting stars, 126, 127; whether attended with crackling sound, 199, 200; intensity of the light, 201.

Bacon, Lord, 53, 58; Novum Organon, 290.

Baer, Von, 337.

Barometer, the increase of its height attended by a depression of the level of the sea, 298; horary oscillations of, 314, 315

Batten, Mr., letter on the snow-line of the two sides of the Himalayas, 331, 332.

Beaufort, Capt., observed the emissions of inflammable gas on the Caramanian coast, as described by Pliny, 223. See also, note by Translator, 223.

Beaumont, Elie de, on the uplifting of mountain chains, 51, 300; influence of the rocks of melaphyre and serpentine, on pendulum experiments, 167; conjectures on the quartz strata of the Col de la Poissoniere, 266.

Baccaria, observation of steady luminous appearance in the clouds, 202; of lightning clouds, unaccompanied by thunder or indication of storm, 337.

Beechey, Capt., 97; observations on the temperature and density of the water of the ocean under different zones of longitude and latitude, 306.

Bembo, Cardinal, his observations on the eruptions of Mount Aetna, 229; theory of the necessity of the proximity of volcanoes to the sea, 243; vegetation on the declivity of Aetna, 347.

Berard, Capt., shooting stars, 119.

Berton, Count, his barometrical measurements of the Dead Sea, 296.

Berzelins on the chemical elements of aerolites, 130, 131.

Benzenberg on meteors and shooting stars, 119, 120; their periodic return in Autgust, 125.

Bessel's theory on the oscillations of the pendulum, 44; pendulum experiments, 64; on the parallax of 61 Cygni, 88; on Halley's comet, 102, 103, 104; on the ascent of shooting stars, 123; on their partial visibility, 128; velocity of the sun's translatory motion, 145; mass of the star 61 Cygni, 148; parallaxes and distances of fixed stars, 153; comparison of measurements of degrees, 165, 166.

Biot on the phenomenon of twilight, 118; on the zodical light, 141; pendulum experiments at Bordeaux, 170.

Biot, Edward, Chinese observations of comets, 101, 109; of aerolites, 128.

Bischof on the interior heat of the globe, 217, 219, 235, 244, 294.

Blumenbach, his classification of the races of men, 356.

Bockh, origin of the ancient myth of the Nemean lunar lion, 134, 135.

Boguslawski, falls of shooting stars, 119, 128.

Bonpland, M., and Humboldt, on the pelagic shells found on the ridge of the Andes, 45.

Boussingault, on the depth at which is found the mean annual temperature within the tropics, 175; on the volcanoes of New Granada, 217; on the temperature of the earth in the tropics, 220, 221; temperature of the thermal springs of Las Trincheras, 222; his investigations on the chemical analysis of the atmosphere, 311, 312; on the mean annual quantity of rain in different parts of South America, 333, 334.

Bouvard, M., 105; his observations on that portion of the horary oscillations of the pressure of the atmosphere, which depends on the attraction of the moon 313.

Bramidos y truenos of Guanaxuato, 209, 210.

Brandes, falls of shooting stars, 114, 116; height and velocity of shooting stars, 120; their periodic falls, 125, 126.

Bravais, on the Aurora, 201; on the daily oscillations of the barometer in 70 degrees north latitude, 314; distribution of the quantity of rain in Central Europe, 334; doubts on the greater dryness of mountain air, 334.

Brewster, Sir David, first detected the connection between the curvature of magnetic lines and my isothermal lines, 193.

Brongniart, Adolphe, luxuriance of the primitive vegetable world, 218; fossil flora contained in coal measures, 280.

Brongniart, Alexander, formation of ribbon jasper, 259; one of the founders of the archaeology of organic life, 273.

Brown, Robert, first discoverer of molecular motion, 341.

Buch's, Leopold von, theory on the elevation of continents and mountain chains, 45; on the craters and circular form of the island of Palma, 226; on volcanoes, 234, 238, 242, 243, 247; on metamorphic rocks, 249-252, 260, 263, 264; on the origin of various conglomerates and rocks of detritus, 269; classification of ammonites, 276, 277; physical causes of the elevation of continents, 295; on the changes in height of the Swedish coasts, 295.

Buckland, 272; on the fossil flora of the coal measures, 279.

Buffon, his views on the geographical distribution of animals, 348.

Burckhardt, on the volcano of Medina, 246; on the hornitos de Jerullo, see note by Translator, 230.

Burnes, Sir Alexander, on the purity of the atmosphere in Bokhara, 114; propagation of shocks of earthquakes, 212.

p 365 Caile, La, pendulum measurements at the Cape of Good Hope, 169.

Caldas, quantity of rain at Santa Fe de Bogota, 334.

Camargo's MS. 'Historia de Tiascala', 140.

Capocci, his observations on periodic falls of aerolites, 126.

Carlini, geodesic experiments in Lombardy, 168; Mount Cenis, 170.

Carrara marble, 262, 263.

Carus, his definition of "Nature," 41.

Caspian Sea, its periodic rise and fall, 297.

Cassini, Dominicus, on the zodiacal light, 139, 140; hypothesis on 141; his discovery of the spheroidal form of Jupiter, 164.

Cautley, Capt, and Dr. Falconer, discovery of gigantic fossils in the Himalayas.

Cavanilles, first entertained the idea of seeing grass grow, 149.

Cavendish, use of the torsion balance to determine the mean density of the Earth, 170.

Challis, Professor, on the Aurora, March 19 and Oct. 24th, 1847, see note by Translator, 195, 199.

Chardin, noticed in Persia the famous comet of 1608, called "nyzek" or "petite lance," 139.

Charpentier, M., belemnites found in the primitive limestone of the Col de la Seigne, 261; glaciers, 329.

Chemistry as distinguished from physics, 62; chemical affinity, 63.

Chevandier, calculations on the carbon contained in the trees of the forests of our temperate zones, 281.

Childrey first described the zodical light in his Britannia Baconica, 138.

Chinese accounts of comets, 99, 100, 101; shooting stars, 128: "fire springs," 158; knowledge of the magnetic needle, 180; electro-magnetism, 188, 189.

Chladni on meteoric stones, etc., 118, 135; on the selenic origin of aerolites, 121; on the supposed phenomenon of ascending shooting stars, 122; on the obscuration of the Sun's disk, 133; sound-figures, 135; pulsations in the tails of comets, 143.

Choiseul, his chart of Lemnos, 246.

Chromatic polarization. See Polarization.

Cirro-cumulus cloud. See Clouds.

Cirrous Strata. See Clouds.

Clark, his experiments on the variations of atmospheric electricity, 335, 336.

Clarke, J. G., of Maine, U.S., on the comet of 1843, 100.

Climatic distribution of heat, 313, 317-328; of humidity, 328, 333, 334.

Climatology, 317-329; climate, general sense of, 317, 318.

Clouds, their electric tension, color, and height, 236, 337; connection of cirrous strata with the Aurora Borealis, 196; cirro-cumulus cloud, phenomena of, 197; luminous, 202; Dove on their formation and appearance, 315, 316; often present on a bright summer sky the "projected image" of the soil below, 316; volcanic, 233.

Coal formations, ancient vegetable remains in, 280, 281.

Coal mines, depth of, 158-160.

Colebrooke on the snow-line of the two sides of the Himalayas, 31.

Colladon, electro-magnetic apparatus, 335.

Columbus, his remark that "the Earth is small and narrow," 164; found the compass showed no variation in the Azores, 181, 182; of lava streams, 245; noticed conifers and palms growing together in Cuba, 282; remarks in his journal on the equatorial currents, 307; of the Sargasso Sea, 308; his dream, 310, 311.

Comets, general description of, 99-112; Biela's 43, 86, 107, 108; Blaupain's 108; Clausen's 108; Encke's, 43, 64, 86, 107-108; Faye's 107, 108; Halley's, 43, 100, 102-109; Lexell's and Burchardt's 108, 110; Messier's 108; Olbera's, 109; Pons's 109; famous one of 1608, seen in Persia, called "nyzek," or "petit lance," 189; comet of 1843, 101; their nucleus and tail, 87, 100; small mass, 100; diversity of form, 100-103; light, 104-106; velocity, 109; comets of short period, 107-109; long period, 109-110; number, 99; Chinese observations on, 99-101; value of a knowledge of their orbits, 43; possibility of collision of Blela's and Encke's comets, 107, 108; hypothesis of a resisting medium conjectured from the diminishing period of the revolution of Encke's comet, 106; apprehensions of their collision with the Earth, 108, 110, 111; their popular supposed influence on the vintage, 111.

Compass, early use of by the Chinese, 180; permanency in the West Indies, 181.

Condamine, La, inscription on a marble tablet at the Jesuit's College, Quito on the use of the pendulum as a measure of seconds, 166, 167.

Conde, notice of a heavy shower of shooting stars, Oct., 902, 119.

Coraboeuf and Delcrois, geodetic operations, 304.

Cordilleras, scenery of, 26, 29, 33; vegetation, 34, 35; intensity of the zodiacal light, 137.

Cosmography, physical, its object and ultimate aims, 57-60; materials, 60.

Cosmos, the author's object, 38, 78; primitive signification and precise definition of the word, 69; how employed by Greek and Roman writers, 69, 60; derivation, 70.

Craters. See Volcanoes.

Curtius, Professor, his notes on the temperature of various springs in Greece, 222, 223.

Cuvier, one of the founders of the archaeology of organic life, 273; discovery of fossil crocodiles in the tertiary formations, 274. Dainachos on the phenomena attending the fall of the stone of Aegos Potamos, 133, 134.

Dalman on the existence of Chionaea araneoides in polar snow, 344.

Dalton, observed the southern lights in England, 198.

Dante, quotation from, 322.

Darwin, Charles, fossil vegetation in the travertine of Van Diemen's Land, 224; central volcanoes regarded as volcanic chains of small extent on parallel fissures, 238; instructive materials in the temperate zones of the southern hemisphere for the study of the present and past geography of plants, 282, 283; on the fiord formation at the southeast end of America, 293; on the elevation and depression of the bottom of the South Sea, 297; rich luxuriance of animal life in the ocean, 309, 310; on the volcano of Aconcagua, 330.

Daubeney on volcanos. See Translator's notes, 161, 203, 204, 210, 218, 224, 228, 230, 233, 234, 235, 236, 244, 245.

Daussy, his barometric expriments, 208; observations on the velocity of the equatorial current, 307.

Davy, Sir Humphrey, hypothesis on active volcanic phenomena, 235; on the low temperature of water on shoals, 309.

Dead Sea, its depression below the level of the Mediterranean, 296, 297.

Dechen, Von, on the depth of the coal-basin of Liege, 160.

Delcrois. See Coraboeuf.

Descartes, his fragments of a contemplated work, entitled "Monde," 68; on comets, 139.

Deshayes and Lyell, their investigations on the numerical relations of extinct and existing organic life, 275.

Dicaearchus, his "parallel of the diaphragm," 289.

Diogenes Laertius, on the aerolite of Aegos Potamos, 116, 122, 134.

D'Orbigny, fossil remains from the Himalaya and the Indian plains of Cutch, 277.

Dove on the similar action of the declination needle to the atmospheric electrometer, 194; "law of rotation," 315; on the formation and appearance of clouds, 316; on the difference between the true temperature of the surface of the ground and the indications of a thermometer suspended in the shade, 325; hygrometric windrose, 333.

Doyere, his beautiful experiments on the tenacity of life in animalcules, 345.

Drake, shaking of the earth for successive days in the United States (1811-12), 211.

Dufrenoy et Elie de Beaumont, Geologie de la France, 253, 258, 259, 260, 262, 266.

Dumas, results of his chemical analysis of the atmosphere, 311.

Dunlop on the comet of 1825, 103.

Duperrey on the configuration of the magnetic equator, 183; pendulum oscillations, 166.

Duprez, influence of trees on the intensity of electricity in the atmosphere, 335.

Eandi, Vassalli, electric perturbation during the protracted earthquake of Pignorol, 206.

Earth, survey of its crust, 72; relative magnitude, etc., in the solar system, 95-97; general description of terrestrial phenomena, 154-360; geographical distribution, 161, 162; its mean density, 169-172; internal heat and temperature, 172-176; electro-magnetic activity, 177-193; conjectures on its early high temperature, 172; interior increase of heat with increasing depth, 161; greatest depths reached by human labor, 157-159; methods employed to investigate the curvature of its surface, 165-168; reaction of the interior on the external crust, 161, 202-247; general delineation of its reaction, 204-206; fantastic views on its interior, 171.

Earthquakes, general account of, 204-218; their manifestations, 204-206; of Riobamba, 204, 206, 208, 212, 214; Lisbon, 210, 211, 213, 214; Calabria, 206; their propagation, 204, 212, 213; waves of commotion, 205, 206, 212; action on gaseous and aqueous springs, 210, 222, 224; salses and mud volcanoes, 224-228; erroneous popular belief on, 206-208; noise accompanying earthquakes, 208-210; their vast destruction of life, 210, 211; volcanic force, 214, 215; deep and peculiar impression produced on men and animals, 215, 216.

Ehrenberg, his discovery of infusoria in the polishing slate of Bilin, 150; infusorial deposits, 255, 262; brilliant discovery of microscopic life in the ocean and in the ice of the polar regions, 342; rapid propogation of animalcules and their tenacity of life, 343-345; transformation of chalk, 262.

Electricity, magnetic, 188-202; conjectured electric currents, 189, 190; electric storms, 194; atmospheric 335, 337.

Elevations, comparative, of mountains in the two hemispheres, 28, 29.

Encke, 106; his computation that the showers of meteors, in 1833, proceeded from the same point of space in the direction in which the earth was moving at the time, 119, 120.

Ennius, 71.

Epicharmus, writings of, 71.

Equator, advantages of the countries bordering on, 33, 34; their organic richness and fertility, 34, 35; magnetic equator, 183-185.

Erman, Adolph, on the three cold days of May (11th-13th), 133; lines of declination in Northern Asia, 182; in the southern parts of the Atlantic, 187; observations during the earthquake of Irkutsk, on the non-disturbance of the horary changes of the magnetic needle, 207.

Eruptions and exhalations (volcanic), lava, gaseous and liquid fluids, hot mud, mud mofettes, etc., 161, [other page numbers obscured in paper copy]

p 367 Ethnographical studies, their importance and teaching, 357, 358.

Euripides, his Phaeton, 122.

Falconer, Dr., fossil researches in the Himalayas, 278.

Faraday, radiating heat, electro-magnetism etc., 49, 179, 188; brilliant discovery of the evolution of light by magnetic forces, 193.

Farquharson on the connection of cirrous clouds with the Aurora, 197; its altitude, 199.

Federow, his pendulum experiments, 168.

Feldt on the ascent of shooting stars, 123.

Ferdinandes, igneous island of, 242.

Floras, geographical distribution of, 350.

Forbes, Professor E., reference to his Travels in Lycia, 223; account of the island of Santorino, 241, 242.

Forbes, Professor J., his improved selsmometer, 205; on the correspondence existing between the distribution of existing floras in the British Islands, 348, 349; on the origin and diffusion of the British flora, 353, 354.

Forster, George, remarked the climatic difference of temperature of the eastern and western coasts of both continents, 321.

Forster, Dr. Thomas, monkish notice of "Meteorodes," 123.

Fossil remains of tropical plants and animals found in northern regions, 46, 270-284; of extinct vegetation in the travertine of Van Diemen's Land, 224; fossil human remains, 250.

Foster, Reinhold, pyramidal configuration of the southern extremities of continents, 290, 291.

Fourier, temperature of our planetary system, 155, 172, 176.

Fracastoro on the direction of the tails of comets from the sun, 101.

Fraehn, fall of stars, 119.

Franklin, Benjamin, existence of sandbanks indicated by the coldness of the water over them, 308.

Franklin, Capt., on the Aurora, 197, 199, 200, 201; rarity of electric explosions in high northern regions, 337.

Freycinet, pendulum oscillations, 166.

Fusinieri on meteoric masses, 123.

Galileo, 104, 167.

Galle, Dr., 91.

Galvant, Aloysio, accidental discovery of galvanism, 52.

Gaseous emanations, fluids, mud, and molten earth, 217, 220.

Gasparin, distribution of the quantity of rain in Central Europe, 333.

Gauss, Friedrich, on terrestrial magnetism, 179; his erection. in 1832, of a magnetic observatory on a new principle, 191, 192.

Gay-Lussac, 204, 233, 234, 266, 267, 311, 312, 334, 336.

Geognostic or geological description of the earth's surface, 202-286.

Geognosy (the study of the textures and position of the earth's surface), its progress, 203.

Geography, physical, 288-311; of animal life, 341-346; of plants, 346-351.

Geographics, Ritter's (Carl), "Geography in relation to Nature and the History of Man," 48, 67; Varenius (Bernhard), General and Comparative Geography, 66, 67.

Gerard, Capts. A. G. and J. G., on the snow-line and vegetation of the Himalayas, 31, 32, 331, 332.

German scientific works, their defects, 47.

Geyser, intermittent fountains of, 222.

Gieseke on the Aurora, 200.

Gilbert, Sir Humphrey, Gulf Stream, 307.

Gilbert, William, of Colchester, terrestrial magnetism, 158, 159, 177, 179, 182.

Gillies, Dr., on the snow-line of South America, 330, 331.

Gioja, crater of, 98.

Girard, composition and texture of basalt, 253.

Glaisher, James, on the Aurora Borealis of Oct. 24, 1847. See Translator's notes, 194, 200.

Goldfuss, Professor, examination of fossil specimens of the flying saurians, 274.

Goppert on the conversion of a fragment of amber-tree into black coal, 281; eyeadeae, 283; on the amber-tree of the Baltic, 283, 284.

Gothe, 41, 47, 53.

Greek philosophers, their use of the term Cosmos, 69, 70; hypotheses on aerolites, 122, 123, 134.

Grimm, Jacob, graceful symbolism attached to falling stars in the Lithuanian mythology, 112, 113.

Gulf Stream, its origin and course, 307.

Gumprecht, pyroxenic nepheline, 253.

Guanaxuato, striking subterranean noise at, 209.

Hall, Sir James, his experiments on mineral fusion, 262.

Halley, comet, 43, 100, 102-109; on the meteor of 1686, 118, 133; on the light of stars, 152; hypothesis of the earth being a hollow sphere, 171; his bold conjecture that the Aurora Borealis was a magnetic phenomenon, 193.

Hansteen on magnetic lines of declination in Northern Asia, 182.

Hausen on the material contents of the moon, 96.

Hedenstrom on the so-called "Wood Hills" of New Siberia, 281.

Hegel, quotation from his "Philosophy of History," 76.

Heine, discovery of crystals of feldspar in scoriae, 268.

Hemmer, falling stars, 119.

Hencke, planets discovered by. See note by Translator, 90, 91.

Henfrey, A., extract from his Outlines of Structural and Physiological Botany. See notes by Translator, 341, 342, 351.

p 368 Hensius on the variations of form in the comet of 1744, 102.

Herodotus, described Scythia as free from earthquakes, 204; Scythian saga of the sacred gold, which fell burning from heaven, 115.

Herschel, Sir William, map of the world, 66; inscription on his monument at Upton, 87; satellites of Saturn, 96; diameters of comets, 101; on the comet of 1811, 103; star guagings, 150; starless space, 150, 152; time required for light to pass to the earth from the remotest luminous vapor, 154.

Herschel, Sir John, letter on Magellanic clouds, 85; satellites of Saturn, 98; diameter of nebulous stars, 141; stellar Milky Way, 150, 151; light of isolated starry clusters, 151; observed at the Cape, the star pi in Argo increase in splendor, 153; invariability of the magnetic declination in the West Indes, 181.

Hesiod, dimensions of the universe, 154.

Hevellus on the comet of 1618, 106.

Hibbert, Dr., on the Lake of Laach. See note by Translator, 218.

Himalayas, the, their altitude, 28; scenery and vegetation, 29, 30; temperature, 30, 31; variations of the snow-line on their northern and southern declivities, 30-33, 331.

Hind, Mr., planets discovered by. See Translator's note, 90, 91.

Hindoo civilization, its primitive seat, 35, 36.

Hippalos, or monsoons, 316.

Hippocrates, his erroneous supposition that the land of Scythia is an elevated table-land, 346.

Hoff, numerical inquiries on the distribution of earthquakes throughout the year, 207.

Hoffman, Friedrich, observations on earthquakes, 206-207; on eruption fissures in the Lipari Islands, 238.

Holberg, his Satire, "Travels of Nic. Klimius, in the world under ground." See Translator's note, 171, 172.

Hood on the Aurora, 200, 201.

Hooke, Robert, pulsations in the tails of comets, 143; his anticipation of the application of botannical and zoological evidence to determine the relative age of rocks, 270-272.

Ho-tsings, Chinese fire-springs, their depth, 158; chemical composition, 217.

Howard on the climate of London, 125; mean annual quantity of rain in London, 333.

Hugel, Carl von, on the elevation of the valley of Kashmir, 32, 33; on the snow-line of the Himalayas, 331.

Humboldt, Alexander von, works by referred to in various notes: Annales de Chimie et de Physique, 31, 305. Annales des Science Naturelles, 28. Ansichten der Natur, 342, 344, 347. Asie Centrale, 28, 31, 33, 115, 158, 159, 160, 204, 217, 219, 225, 245, 251, 252, 260, 289, 290, 291, 292, 296, 300, 301, 303-306, 320, 323, 324, 330, 331, 334, 350, 356. Atlas Geographique et Physique du Nouveau Continent, 33, 249. De distributione Geographica Plantrum, secundum coeli temperiem, et altitudinem Montium, 33, 291, 324. Examen Critique de l'Histoire de la Geographie, 58, 180, 181, 227, 289, 292, 307, 308, 310, 316, 356. Essai Geognostique sur le Gisement des Roches, 230, 252, 266, 300. Essai Politique sur la Nouvelle Espagne, 129, 240. Essai sur la Geographie des Plantes, 33, 230, 315. Flora Friburgensis Subterranea, 340, 346. Journal de Physique, 178, 292. Lettre au Duc de Sussex, sur les Moyens propres a perfectionner la connaissance du Magnetisme Terrestre, 178, 192. Monumens des Peuples Indigenes de l'Amerique, 140. Nouvelles Annales des Voyages, 307. Recueil d'Observations Astronomiques, 28, 167, 218, 327. Recueil d'Observations de Zoologi et d'Anatomie Comparee, 232. Relation Historique du Voyage aux Regions Equinoxiales, 113, 119, 123, 127, 130, 186, 206, 207, 220, 221, 225, 252, 292, 299, 300, 302, 305-307, 314, 315, 327, 329, 334, 336. Tableau Physique des Regions Equinoxiales, 33, 230. Vues des Cordilleres, 225, 230.

Humboldt, Wilhelm von, on the primitive seat of Hindoo civilization, 36; sonnet, extract from, 154; on the gradual recognition by the human race of the bond of humanity, 358, 359.

Humidity, 313, 332-335.

Hutton, Capt. Thomas, his paper on the snow-line of the Himalayas, 331, 332.

Huygens, polarization of light, 52; nebulous spots, 138.

Hygrometry, 332, 333; hygrometric wind-rose, 333.

Imagination, abuse of, by half-civilized nations, 37.

Imbert, his account of Chinese "fire-springs," 158.

Ionian school of natural philosophy, 65, 77, 84, 134.

Isogenic, isoclinical, isodynamic, etc. See Lines.

Jacquemont, Victor, his barometrical observations on the snow-line of the Himalayas, 32, 231.

Jasper, its formation, 259-261.

Jessen on the gradual rise of the coast of Sweden, 295.

Jorullo, hornitos de, 230.

p 369 Justinian, conjectures on the physical causes of volcanic eruptions, 243.

Kamtz, isobarometric lines, 315; doubts on the greater dryness of mountain air, 334.

Kant, Emmanuel, "on the theory and structure of the heavens," 50, 65; earthquake at Lisbon, 210.

Kelihau on the ancient sea-line of the coast of Spitzbergen, 296.

Kepler on the distances of stars, 88; on the density of the planets, 93; law of progression, 95; on the number of comets, 99; shooting stars, 113; on the obscuration of the sun's disk, 132; on the radiations of heat from the fixed stars, 136; on a solar atmosphere, 139.

Kloden, shooting stars, 119, 124.

Knowledge, superficial, evils of, 43.

Krug of Nidda, temperature of the Geyser and the Strokr intermittent fountains, 222.

Krusenstern, Admiral, on the train of a fire-ball, 114.

Kuopho, a Chinese physicist on the attraction of the magnet, and of amber, 168.

Kupffer, magnetic stations in Northern Asia, 191.

Lamanon, 187.

Lambert, suggestion that the direction of the wind be compared with the height of the barometer, alterations of temperature, humidity, etc., 315.

Lamont, mass of Uranus, 93; satellites of Saturn, 96.

Language and thought, their mutual alliance, 56; author's praise of his native language, 56.

Languages, importance of their study, 357, 359.

Laplace, his "Systeme du Monde," 48, 62, 92, 141; mass of the comet of 1770, 107; on the required velocity of masses projected from the Moon, 121, 122; on the altitude of the boundaries of the atmosphere of cosmical bodies, 141; zodiacal light, 141; lunar inequalities, 166; the Earth's form and size inferred from lunar inequalities, 168, 169; his estimate of the mean height of mountains, 301; density of the ocean required to be less than the earth's for the stability of its equilibrium, 305; results of his perfect theory of tides, 306.

Latin writers, their use of the term "Mundus," 70, 71.

Latitudes, Northern, obstacles they present to a discovery of the laws of Nature, 36; earliest acquaintance with the governing forces of the physical world, there displayed, 36; spread from thence of the germs of civilization, 36.

Latitudes, tropical, their advantages for the contemplation of nature, 33; powerful impressions, from their organic richness and fertility, 34; facilities they present for a knowledge of the laws of nature, 35; brilliant display of shooting stars, 113.

Laugier, his calculations to prove Halley's comet identical with the comet of 1378, described in Chinese tables, 109.

Lava, its mineral composition, 234.

Lavoisier, 62.

Lawrence (St.), fiery tears, 124; meteoric stream, 125.

Leibnitz, his conjecture that the planets increase in volume in proportion to their increase of distance from the Sun, 93.

Lenz, observations on the mean level of the Caspian Sea, 297; maxims of density of the oceanic temperature, 304; temperature and density of the ocean under different zones of latitude and longitude, 306.

Leonhard, Karl von, assumption on formations of granular limestone, 263.

Leverrier, planet Neptune. See Translator's note, 90, 91.

Lewy, observations on the varying quantity of oxygen in the atmosphere, according to local conditions, or the seasons, 311, 312.

Lichtenberg, on meteoric stones, 118.

Liebig on traces of ammonical vapors in the atmosphere, 311.

Light, chromatic polarization of, 52; transmission, 88; of comets, 104-106; of fixed stars, 105; extraordinary lightness, instances of, 142-144; propagation of 153; speed of transit, 153, 154. See Aurora, Zodiacal Light, etc.

Lignites or beds of brown coal, 283, 284.

Lines, isogonic (magnetic equal deviation), 177, 181-185; isoclinal (magnetis equal inclination), 178, 179, 181-185; isodynamic (or magnetic equal force), 181, 185-194; isogeothermal (chthonisothermal), 219; isobarometric, 315; isothermal, isotheral, and isochimenal, 317, 327, 328, 358.

Line of no variation of horary declination, 183; lower limit of perpetual snow, 329-332; phosphorescent, 113.

Lisbon, earthquake of, 210, 211, 213, 214.

Lord on the limits of the snow-line on the Himalayas, 32.

Lottin, his observations of the Aurora, with Bravais and Siljerstrom, on the coast of Lapland, 195, 200, 201.

Lowenorn, recognized the coruscation of the polar light in bright sunshine, 196.

Lyell, Charles, investigations on the numerical relations of extinct and organic life, 274, 275; nether-formed or hypogene rocks, 249; uniformity of the production of erupted rocks, 257. See notes by Translator, 203, 244, 257.

Mackenzie, description of a remarkable eruption in Iceland, 236.

Maclear on a Centauri, 88; parallaxes and distances of fixed stars, 153; increase in brightness of 'pi' Argo, 153.

Madler, planetary compression of Uranus, 96; distance of the innermost satellite of Saturn from the centre of that planet, 97; material contents of the Moon, 96; its libration, 98; mean depression of temperature on the three cold days of May (11th-13th), 133; conjecture that the average mass of the larger number of binary stars exceeds the mass of the Sun, 149.

Magellanic clouds, 85.

Magnetic attraction, 188; declination, 181-183; horary motion, 177-180; horary variations 183, 190; magnetic storms, 177, 179, 195, 199; their intimate connection with the Aurora, 193-201; represented by three systems of lines, see Lines; movement of oval systems, 182; magnetic equator, 183-185; magnetic poles, 183, 184; observatories, 190-192; magnetic stations, 190, 191, 317.

Magnetism, terrestrial, 177-193, 201; electro, 177-191.

Magnussen, Soemund, description of remarkable eruption in Iceland, 236.

Mahlmann, Wilhelm, south west direction of the aërial current in the middle latitudes of the temperate zone, 317.

Mairan on the zodiacal light, 138, 139, 142; his opinion that the Sun is a nebulous star, 141.

Malapert, annular mountain, 98.

Malle, Dureau de la, 223.

Man, general view of, 351-359; proofs of the flexibility of his nature, 27; results of his intellectual progress, 53, 54; geographical distribution of races, 351-356; on the assumption of superior and inferior races, 351-358; his gradual recognition of the bond of humanity, 358, 359.

Mantell, Dr., his "Wonders of Geology," see notes by Translator, 45, 64, 203, 274, 278, 281, 283, 284, 287; "Medals of Creation," 46, 271, 283, 287.

Margarita Philosophica by Gregory Reisch, 58.

Marius, Simon, first described the nebulous spots in Andromeda and Orion, 138.

Martins, observations on polar bands, 198; found that air collected at Faulhorn contained as much oxygen as the air of Paris, 312; on the distribution of the quantity of rain in Central Europe, 333; doubts on the greater dryness of mountain air, 334.

Matthessen, letter to Arago on the zodiacal light, 142.

Mathieu on the augmented intensity of the attraction of gravitation in volcanic islands, 167.

Mayer, Tobias, on the motion of the solar system, 146, 148.

Mean numerical values, their necessity in modern physical science, 81.

Melloni, his discoveries on radiating heat and electro-magnetism, 49.

Menzel, unedited work by, on the flora of Japan, 347.

Messier, comet, 108; nebulous spot resembling our starry stratum, 151.

Metamorphic Rocks. See Rocks.

Meteorology, 311-339.

Meteors, see Aërolites; meteoric infusoria, 345, 346.

Methone, Hill of, 240.

Meyen on forming a thermal scale of cultivation, 324; on the reproductive organs of liverworts and algae, 341.

Meyer, Hermann von, on the organization of flying saurians, 274.

Milky Way, its figure, 89; views of Aristotle on, 103; vast telescopic breadth, 150; Milky Way of nebulous spots at right angles with that of the stars, 151.

Minerals, artificially formed, 268, 269.

Mines, greatest depth of, 157, 159; temperature, 158.

Mist, phosphorescent, 142.

Mitchell, protracted earthquake shocks in North America, 211.

Mitscherlich on the chemical origin of iron glance in volcanic masses, 234; chemical combinations, a means of throwing a clear light on geognosy, 256; on gypsum, as a uniaxal crystal, 259; experiments on the simultaneously opposite actions of heat on crystalline bodies, 259; formation of crystals of mica, 260; on artificial mineral products, 268, 271.

Mofettes (exhalations of carbonic acid gas), 215-219.

Monsoons (Indian), 316, 317.

Monticelli on the current of hydrochloric acid from the crater of Vesuvius, 235; crystals of mica found in the lava of Vesuvius, 260.

Moon, the, its relative magnitude, 96; density, 96; distance from the earth, 97; its libration, 98, 163; its light compared with that of the Aurora, 201, 202; volcanic action in, 228.

Moons or satellites, their diameter, distances, rotation, etc., 95-99.

Morgan, John H. "on the Aurora Borealis of Oct. 24, 1847." See Translator's notes, 194, 199.

Morton, Samuel George, his magnificent work on the American Races, 362.

Moser's images, 202.

Mountains, in Asia, America, and Europe, their altitude, scenery, and vegetation, 27-30, 238, 347; their influence on climate, natural productions, and on the human race, its trade, civilization, and social condition, 291, 292, 299, 300, 327; zones of vegetation on the declivities of 29, 30, 327-329; snow-line of, 30-33, 330, 331.

Mud volcanoes. See Salses and Volcanoes.

Muller, Johannes, on the modifications of plants and aniimals within certain limitations, 353.

Muncke on the appearance of Auroras in certain districts, 198.

Murchison, Sir R., account of a large fissure through which melaphyre had been ejected, 258; classification of fossiliferous strata, 277; on the age of the Palaeosaurus and Thecodontosaurus of Bristol, 274.

Muschenbroek on the frequency of meteors in August, 125.

Myndius, Apollonius, on the Pythagorean doctrine of comets, 103, 104.

Nature, result of a rational inquiry into, 25; emotions excited by her contemplation, 25; striking scenes, 26; their sources of enjoyment, 26, 27; magnificence of the tropical scenery, 33, 34, 35, 344; religious impulses from a communion with nature, 37; obstacles to an active spirit of inquiry, 37; mischief of inaccurate observations, 38; higher enjoyments of her study, 38; narrow-minded views of nature, 38; lofty impressions produced on the minds of laborious observers, 40; nature defined, 41; her studies inexhaustible, 41; general observations, their great advantages, 42; how to be correctly comprehended, 72; her most vivid impressions earthly, 82.

Nature, philosophy of, 24, 37; physical description of, 66, 67, 73.

Nebulae, 84-86; nebulous Milky Way at right angles with that of the stars, 150-153; nebulous spots, conjectures on, 83-86; nebulous stars and planetary nebulae, 85, 151, 152; nebulous vapor, 83-86, 87, 152; their supposed condensation in conformity with the laws of attraction, 84.

Neilson, gradual depression of the southern part of Sweden, 295.

Nericat, Andrea de, popular belief in Syria on the fall of aerolites, 123.

Newton, discussed the question on the difference between the attraction of masses and molecular attraction, 63; Newtonian axiom confirmed by Bessel, 64; his edition of the Geography of Varenius, 66; Principia Mathematica, 67; considered the planets to be composed of the same matter with the Earth, 132; compression of the Earth, 165.

Nicholl, J. P., note from his account of the planet Neptune, 90, 91.

Nicholson, observations of lighting clouds, unaccompanied by thunder or indications of storm, 337.

Nobile, Antonio, experiments of the height of the barometer, and its influence on the level of the sea, 298.

Noggerath counted 792 annual rings in the trunk of a tree at Bonn, 283.

Nordmann on the existence of animalcules in the fluids of the eyes of fishes, 345.

Norman, Robert, invented the inclinatorium, 179.

Observations, scientific, mischief of inaccurate, 38; tendency of unconnected, 40.

Ocean, general view of, 292-311; its extent as compared with the dry land, 288, 289; its depth, 160, 302; tides, 304, 305; decreasing temperature at increased depths, 302; uniformity and constancy of temperature in the same spaces, 303; its currents and their various causes, 306-309; its phosphorescence in the torrid zone, 202; its action on climate, 303, 319-320; influence on the mental and social condition of the human race, 162, 291, 292, 294, 310; richness of its organic life, 300, 310; oceanic microscopic forms, 342, 343; sentiments excited by its contemplation, 310.

Oersted, electro-magnetic discoveries, 188, 191.

Olbers, comets, 104, 109; aerolites, 114, 118; on their planetary velocity, 121; on the supposed phenomena of ascending shooting stars, 123; their periodic return in August, 125; November stream, 126; prediction of a brilliant fall of shooting stars in Nov., 1867, 127; absence of fossil meteoric stones in secondary and tertiary formations, 131; zodiacal light, its vibration through the tails of comets, 143; on the transparency of celestial space, 152.

Olmsted, Denison of New Haven, Connecticut, observations of aerolites, 113, 118, 119, 124.

Oltmanns, Herr, observed continuously with Humboldt, at Berlin, the movements of the declination needle, 190, 191.

Ovid, his description of the volcanic Hill of Methone, 240.

Oviedo describes the weed of the Gulf Stream as Praderias de yerva (sea weed meadows), 308.

Palaeontology, 270-284.

Pallas, meteoric iron, 131.

Palmer, New Haven, Connecticut, on the prodigious swarm of shooting stars, Nov. 12 and 13, 1833, 124; on the non-appearance in certain years of the August and November fall of aerolites, 129.

Parallaxes of fixed stars, 88, 89; of the solar system, 145, 146.

Perry, Capt., on Auroras, their connection with magnetic perturbations, 197, 201; whether attended with any sound, 200; seen to continue throughout the day, 197; barometric observation at Port Bowen, 314, 315; rarity of electric explosions in northern regions, 337.

Patricius, St., his accurate conjectures on the hot springs of Carthage, 223, 224.

Peltier on the actual source of atmospheric electricity, 335, 336.

Pendulum, its scientific uses, 44; experiments with, 64, 166, 169, 170; employed to investigate the curvature of the earth's surface, 165; local attraction, its influence on the pendulum, and geognostic knowledge deduced from, 44, 45, 167, 168; experiments of Bessel, 64.

Pentland, his measurements of the Andes, 28.

Percy, Dr., on minerals artifically produced. See note by Translator, 268.

Permian system of Murchison, 277.

Perouse, La, expedition of, 186.

Persia, great comet seen in (1608), 139, 140.

Pertz on the large aerolite that fell in the bed of the River Narni, 116.

Peters, Dr., velocity of stones projected from Aetna, 122.

Peucati, Count Mazari, partial infection of calcareous beds by the contact of syenitic granite in the Tyrol, 262.

Phillips on the temperature of a coalmine at increasing depths, 174.

Philolaus, his astronomical studies, 65; his fragmentary writings, 68-71.

Philosophy of nature, first germ, 37.

Phosphorescence of the sea in the torrid zones, 202.

Physics, their limits, 50; influence of physical science on the wealth and prosperity of nations, 53; province of physical science, 59; distinction betweeen the physical 'history' and physical 'description' of the world, 71, 72; physical science, characteristics of its modern progress, 81.

Pindar, 227.

Plans, geodesic experiments in Lombardy, 168.

Planets, 89-99; present number discovered, 90. (See note by Translator on the most recent discoveries, 90, 91); Sir Isaac Newton on their composition, 132; limited physical knowledge of, 156, 157; Ceres, 64-92; Earth, 88-99; Juno, 64, 92-97, 106; Jupiter, 64, 87, 92-98, 202; Mars, 87, 91-94, 132; Mercury, 87, 92-94; Pallas, 64, 92; Saturn, 87, 92-94; Venus, 91-94, 202; Uranus, 90-94; planets which have the largest number of moons, 95, 96.

Plants, geographical distribution of, 346-350.

Plato on the heavenly bodies, etc., 69; interpretation of nature, 163; his geognostic views on hot springs, and volcanic igneous streams, 237, 238.

Pliny the elder, his Natural History, 73; on comets, 104; aerolites, 122, 123, 130; magnetism, 180; attraction of amber, 188; on earthquakes, 205, 207; on the flame of inflammable gas, in the district of Phasells, 223; rarity of jasper, 261; on the configuration of Africa, 292.

Pliny the younger, his description of the great eruption of Mount Vesuvius, and the phenomenon of volcanic ashes, 235.

Plutarch, truth of his conjecture that falling stars are celestial bodies, 133, 134.

Poisson on the planet Jupiter, 64; conjecture on the spontaneous ignition of meteoric stones, 118; zodiacal light, 141; theory on the earth's temperature, 172, 173, 174, 176, 177.

Polarization, chromatic, results of its discovery, 52; experiments on the light of comets, 105, 106.

Polybius, 291.

Posidonius on the Ligyran field of stones, 115, 116.

Pouilet on the actual source of atmospheric electricity, 335.

Prejudices against science, how originated, 38; against the study of the exact sciences, why fallacious, 40-52.

Prichard, his physical history of Mankind, 352.

Pseudo-Plato, 54.

Psychrometer, 332, 338.

Pythagoras, first employed the word Cosmos in its modern sense, 69.

Pythagoreans, their study of the heavenly bodies, 65; doctrine on comets, 103.

Quarterly Review, article on Terrestrial Magnetism, 192.

Quetelet on aerolites, 114; their periodic return in August, 125.

Races, human, their geographical distribution, and unity, 351, 359.

Rain drops, temperature of, 220; mean annual quantity in the two hemispheres, 333, 334.

Reich, mean density of the earth, as ascertained by the torsion balance, 170; temperature of the mines in Saxony, 174.

Reisch, Gregory, his "Margarita Philosophica," 58.

Remusat, Abel, Mongolian tradition on the fall of an aerolite, 116; active volcanoes in Central Asia, at great distances from the sea, 245.

Richardson, magnetic phenomena attending the Aurora, 197; whether accompanied by sound 200; influence on the magnetic needle of the Aurora, 201.

Riohamba, earthquake at, 204, 205, 208, 213, 214.

Ritter, Carl, on his "Geography in relation to Nature and the History of Man," 48, 67.

Robert, Eugene, on the ancient sea-line on the coast of Spitzbergen, 296.

Robertson on the permanency of the compass in Jamaica, 181.

Rocks, their nature and configuration, 228; geognostical classification into four groups, 248-251; i. rocks of eruption, 248, 251-253; ii. sedimentary rocks, 248, 254, 255; iii. transformed, or metamorphic rocks, 248, 259, 255, 256-269; iv. conglomerates, or rocks of detritus, 269, 270; their changes from the action of heat, 258, 259; phenomena of contact, 258-269; effects of pressure and the rapidity of cooling, 258, 267.

Rose, Gustav, on the chemical elements, etc., of various aerolites, 131; on the structural relations of volcanic rocks, 254; on crystals of feldspar and albite found in granite, 251; relations of position in which granite occurs, 252-269; chemical process in the formation of various minerals, 265-269.

Ross, Sir James, his soundings with 27,000 feet of line, 160; magnetic observations at the South Pole, 187; important results of the Antarctic magnetic expedition in 1839, 192; rarity of electric explosions in high northern regions, 337.

Rossell, M. de, his magnetic oscillation experiments, and their date of publication, 186, 187.

Rothmann, confounded the setting zodiscal light with the cessation of twilight, 143.

Rozier, observation of a steady luminous appearance in the clouds, 202.

Rumker, Encke's comet, 106.

Ruppell denies the existence of active volcanoes in Kordofan, 245.

Sabine, Edward, observations on days of unusual magnetic disturbances, 178; recent magnetic observations, 184, 185, 187, 188.

Sagra, Ramon de la, observations on the mean annual quantity of rain in the Havana, 333.

Saint Pierre, Bernardin de, Paul and Virginia, 26; Studies of Nature, 347.

Salses or mud volcanoes, 224-228; striking phenomena attending their origin, 224, 225.

Salt works, depth of 158, 159; temperature, 174.

Santorino, the most important of the islands of eruption, 241, 242; description of. See note by Translator, 241.

Sargasso Sea, its situation, 308.

Satellites revolving round the primary planets, their diameter, distance, rotation, etc., 94, 99; Saturn's 96-98, 127' Earth's see Moon, Jupiter's, 96, 97; Uranus, 96-98.

Saurians, flying, fossil remains of, 274, 275.

Saussure, measurements of the marginal ledge of the crater of Mount Vesuvius, 232; traces of ammoniacal vapors in the atmosphere, 311; hygrometric measurements with Humboldt, 334-336.

Schayer, microscopic organisms in the ocean, 342, 343.

Scheerer on the identity of eleolite and nepheline, 253.

Schelling on nature, 55; quotation from his Giordino Bruino, 77.

Scheuchzner's fossil salamander, conjectured to be an antediluvian man, 274.

Schiller, quotation from, 36.

Schnurrer on the obscuration of the sun's disk, 133.

Schouten, Cornelius, in 1616 found the declination null in the Pacific, 182.

Schouw, distribution of the quantity of rain in Central Europe, 333.

Schrieber on the fragmentary character of meteoric stones, 117.

Scientific researches, their frequent result, 50; scientific knowledge a requirement of the present age, 53, 54; scientific terms, their vagueness and misapplication, 58, 68.

Scina, Abbate, earthquakes unconnected with the state of the weather, 206, 207.

Scoresby, rarity of electric explosions in high northern regions, 337.

Sea. See Ocean.

Seismometer, the, 205.

Seleucus of Erythrea, his astronomical studies, 65.

Seneca, noticed the direction of the tails of comets, 102; his views on the nature and paths of comets, 103, 104; omens drawn from their sudden appearance, 111; the germs of later observations on earthquakes found in his writings, 207; problematical extinction and sinking of Mount Aetna, 227, 240.

Shoals, atmospheric indications of their vicinity, 309.

Sidereal systems, 89, 90.

Siljerstrom, his observations on the Aurora, with Lottin and Bravais, on the coast of Lapland, 195.

Sirowatskoi, "Wood Hills" in New Siberia, 281.

Snow-line of the Himalayas, 30-33, 331, 334; of the Andes, 330; redness of long-fallen snow, 344.

Solar system, general description, 90-154; its position in space, 89; its transistory motion, 145-150.

Solinus on mud volcanoes, 225.

Sommering on the fossil remains of the large vertebrata, 274.

Somerville, Mrs., on the volume of fire-balls and shooting stars, 116; faintness of light of planetary nebulae, 141.

Southern celestial hemisphere, its picturesque beauty, 85, 86.

Spontaneous generation, 345, 346.

Springs, hot and cold, 219-225; intermittent, 219; causes of their temperature, 220-222; thermal, 222, 345; deepest Artesian wells the warmest, observed by Arago, 223; salses, 224-226; influence of earthquake shocks on hot springs, 210, 222-224.

Stars, general account of, 85-90; fixed 89, 90, 104; double and multiple, 89, 147; nebulous, 85, 86, 151, 152; their translatory motion, 147-150; parallaxes and distances, 147-149; computations of Bessel and Herschel on their diameter and volume, 148; immense number in the Milky Way, 150, 151; star dust, 85; star gaugings, 150; starless spaces, 150, 152; telescopic stars, 152; velocity of the propagation of light of, 153, 154; apparition of new stars, 153.

Storms, magnetic and volcanic. See Magnetism, Volcanoes.

Strabo, observed the cessation of shocks of erthquake on the eruption of lava, 215; on the mode in which islands are formed, 227; description of the Hill of Methone, 240; volcanic theory, 243; divined the existence of a continent in the northern hemisphere between Theria and Thine, 289; extolled the varied form of our small continent as favorable to the moral and intellectual development of its people, 291, 292.

Struve, Otho, on the proper motion of the solar system, 146; investigations on the propagation of light, 153; parallaxes and distances of fixed stars, 153; observations on Halley's comet, 105.

Studer, Professor, on mineral metamorphism. See note by Translator, 248.

Sun, magnitude of its volume compared with that of the fixed stars, 136; obscuration of its disk, 132; rotation round the center of gravity of the whole solar system, 145; velocity of its translatory motion, 145; narrow limitations of its atmosphere as compared with the nucleus of other nebulous stars, 141; "sun stones" of the ancients, 122; views of the Greek philosophers on the sun, 122.

Symond, Lieut., his trigonometrical survey of the Dead Sea, 296, 297.

Tacitus, distinguished local climatic relations from those of race, 352.

Temperature of the globe, see Earth and Ocean; remarkable uniformity over the same spaces of the surface of the ocean, 303; zones at which occur the maxima of the oceanic temperature, 319; causes which lower the temperature, 319, 320; temperature of various places, annual, and in the different seasons, 322, 323-328; thermic scale of temperature, 324, 325; of continental climates as compared with insular and littoral climates, 321, 322; law of decrease with increase of elevation, 327; depression of, by shoals, 309; refrigeration of the lower strata of the ocean, 303.

Teneriffe, Peak of its striking scenery, 26.

Theodectes of Phaselis on the color of the Ethiopians, 353.

Theon of Alexandria described comets as "wandering light clouds," 100.

Theophylactus described Scythia as free from earthquakes, 204.

Thermal scales of cultivated plants, 324, 325.

Thermal springs, their temperature, constancy, and change, 221-224; animal and vegetable life in, 345.

Thermometer, 338.

Thibet, habitability of its elevated plateaux, 331, 332.

Thienemann on the Aurora, 197, 200.

Thought, results of its free action, 53, 54; union with language, 56.

Tiberias, Sea of, its depression below the level of the Mediterranean, 296.

Tides of the ocean, their phenomena, 305, 306.

Tillard, Capt., on the sudden appearance of the island of Sabrina, 242.

Tournefort, zones of vegetation on Mount Ararat, 347.

Tralles, his notice of the negative electricity of the air near high waterfalls, 336.

Translator, notes by, 29; on the increase of the earth's internal heat with increase of depth, 45; silicious infusoria and animalculites, 46; chemical analysis of an aerolite, 64; on the recent discoveries of planets, 90, 91; observed the comet of 1843, at New Bedford, Massachusetts, in bright sunshine, 101; on meteoric stones, 111; on a MS., said to be in the library of Christ's College, Cambridge, 124; on the term "salses," 161; on Holberg's satire, "Travels in the World under Ground," 171; on the Aurora Borealis of Oct. 24, 1847, 194, 195, 199; on the electricity of the atmosphere during the Aurora, 200; on volcanic phenomena, 203, 204; description of the seismometer, 205; on the great earthquake of Lisbon, 210; impression made on the natives and foreigners by earthquakes in Peru, 215; earthquakes at Lima, 216, 217; on the gaseous compounds of sulphur, 217, 218; on the Lake of Lasch, its craters, 218; on the emissions of inflammable gas in the district of Phasells, 233; on true volcanoes as distinguished from salses, 224; on the volcano of Pichincha, 228; on the hornitos de Jorullo, as seen by Humboldt, 230; general rule on the dimensions of craters, 230; on the ejection of fish from the volcano of Imbaburn, 223; on the little isle of Volcano, 234; volcanic steam of Pantellaria, 235; on Daubeney's work "On Volcanoes," 236; account of the island of Santorino, 241; on the vicinity of extinct volcanoes to the sea, 244; meaning of the Chinese term "li," 245; on mineral metamorphism, 248; on fossil human remains found in Guadaloupe, 250; on minerals artifically produced 267, 268; fossil organic structures, 271, 272; on Coprolites, 271; geognostic distribution of fossils, 276; fossil fauna of the Sewalik Hills, 278; thickness of coal measures, 281; on the amber pine forests of the Baltic, 283, 284; elevation of mountain chains, 286, 287; the dinornis of Owen, 287; depth of the atmosphere, 302; richness of organic life in the ocean, 309; on filaments of plants resembling the spermatozoa of animals, 341; on the Diatomaceae in the South Arctic Ocean, 343; on the distribution of the floras and faunas of the British Isles, 348, 349; on the origin and diffusion of the British flora, 353, 354.

Translatory motion of the solar system, 145-150.

Trogus, Pompeius, on the supposed necessity that volcanoes were dependent on their vicinity to the sea for their continuance, 243, 244; views of the ancients on spontaneous generation, 346.

Tropical latitudes, their advantages for the contemplation of nature, 33; powerful impressions from their organic richness and fertility, 34; facilities they present for a knowledge of the laws of nature 35; transparency of the atmosphere, 114; phosphorescence of the sea, 202.

Tschudi, Dr., extract from his "Travels in Peru." See Translator's note, 215, 216, 217.

Turner, note on Sir Isaac Newton, 132.

Universality of animated life, 342, 343.

Valz on the comet of 1618, 106.

Varenius, Bernhard, his excellent general and comparative Geography, 66, 67; edited by Newton, 66.

Vegetable world, as viewed with microscopic powers of vision, 341; its predominance over animal life, 343.

Vegetation, its varied distribution on the earth's surface, 29-31, 62; richness and fertility in the tropics, 33-35; zones of vegetation on the declivities of mountains, 29-32, 346-350. See Aetna, Cordilleras, Himalayas, Mountains.

Vico, satellites of Saturn, 96.

Vigne, measurement of Ladak, 322.

Vine, thermal scale of its cultivation, 324.

Volcanoes, 28, 30, 35, 159, 161, 214, 215, 224-248; author's application of the term volcanic, 45; active volcanoes, safety-valves for their immediate neighborhood, 214; volcanic eruptions, 161, 210-270; mud volcanoes or salses, 224-228; traces of volcanic action on the surface of the earth and moon, 228; influence of relations of height on the occurrence of eruptions, 228-233; volcanic storm, 233; volcanic ashes, 233; classification of volcanoes into central and linear, 238; theory of the necessity of their proximity to the sea, 243-246; geographical distribution of still active volcanoes, 245-247; metamorphic action on rocks, 247-249.

Vrolik, his anatomical investigations on the form of the pelvis, 352, 353.

Wagner, Rudolph, notes on the races of Africa, 352.

Walter on the decrease of volcanic activity, 215.

Wartmann, meteors, 113, 114.

Weber, his anatomical investigations on the form of the pelvis, 353.

Webster, Dr. (of Harvard College, U.S.), account of the island named Sabrina. See note by Translator, 242.

Winds, 315-321; monsoons, 316, 317; trade winds, 32-, 321; law of rotation, importance of its knowledge, 315-317.

Wine on the temperature required for its cultivation, 324; thermic table of mean annual heat, 325.

Wolleston on the limitation of the atmosphere, 302.

Wrangel, Admiral, on the brilliancy of the Aurora Borealis, coincident with the fall of shooting stars, 126, 127; observations of the Aurora, 197, 200; wood hills of the Siberian Polar Sea, 281.

Xenophanes of Colophon, described comets as wandering light clouds, 100; marine fossils found in marble quarries, 263.

Young, Thomas, earliest observer of the influence different kinds of rocks exercise on the vibrations of the pendulum, 168.

Yul-sung, described by Chinese writers as "the realm of pleasure," 332.

Zimmerman, Carl, hypsometrical remarks on the elevation of the Himalayas, 32.

Zodiacal light, conjectures on, 86-92; general account of, 137-144; beautiful appearance, 137, 138; first described in Childrey's Britannia Baconica, 138; probable causes, 141; intensity in tropical climates, 142.

Zones, of vegetation, on the declivities of mountains, 29-33; of latitude, their diversified vegetation, 62; of the southern heavens, their magnificence, 85, 86; polar, 197, 198.

END OF VOL. I.