Part 14

In every part of the solar vortex the ether is continually pressing outwards. We are not now speaking of the radial stream, but of the slower spiral motion of the ether around the axis of the vortex, whose centrifugal force is bearing the whole body of the ether outwards, thus rarefying the central parts, and thus giving rise to the polar influx, from which arises the radial stream. This may be made more intelligible, by reflecting that the polar current is comparatively dense ether, and that the length of the axis of the vortex prevents this influx current coming in sufficient quantities to restore an equilibrium in the density of the medium. Yet, what does come down the poles, is distributed rapidly along the equatorial plane, leaving the space still rarefied. Now we perceive, that in order for the radial stream to continue in action, requires the whole medium of the vortex to be also moving outward; it is therefore continually condensed as it proceeds. This condensation necessarily converts much of the specific heat of the ether into sensible heat; so that the temperature of the medium is continually increasing, as the distance from the sun increases.

When we contemplate the solar system as the emanation of one Great Mind, we naturally seek for evidence of the wisdom of a supreme intelligence in all the arrangements of that system. But, however humbly and reverently we may speak of these arrangements, we can scarcely avoid the wish, that the planetary distances had been differently arranged, if Newton's doctrine be true, that space is a vacuum, and that the heat of a planet, is inversely as the squares of the distances from the sun. For, to speak of the temperature of space, except as dependent on this law, is one of those many incomprehensible inconsistencies with which philosophers are chargeable. If the Newtonian philosophy is literally true, space has no temperature, and the surface heat of the planet Neptune is nearly 1,000 times less than on our own globe. Again, on Mercury it is seven times greater, which heat would scorch and consume every organic substance on the earth, and speedily envelope the boiling ocean in a shroud of impermeable vapor. Granting even that space may not be a vacuum, and yet the law of gravitation be true, we may still be allowed to consider both Saturn and Uranus and Neptune, as inhospitable abodes for intelligent creatures; and, seeing the immensity of room in the system, there is no reason why these planets might not have been permitted to revolve nearer the great source of light and life and cheering emanations. To suggest the resources of Omnipotence is no argument. He has surrounded us with analogies which are seen, by which we may attain a knowledge of those which are not seen; and we have every reason to suppose that the great Author of nature is not indifferent to the aspects under which his works reveal him unto his creatures. Yet there is (on the above hypothesis) an apparent want of harmony in the planetary distances; and if frail mortality may be permitted to speak out, an explanation is needed to obviate this seeming anomaly in the economy of the world. The more we learn of the physical arrangements of the universe, the more do they correspond with our experience of the nice adaptation of the means to the end which obtains in our own globe, and we can only judge of other planets by the analogies around us. Here, there, are extremes of temperature it is true: it is necessary there should be, and we can see and understand the necessity in all such cases, and how they conduce to the general average of good. But, astronomers can give no reason why it is necessary that some planets of our system should be placed so remote that the sun is frittered down to a star, whose heatless light is but a mockery to those frigid realms.

Now, according to this theory, the temperature of Neptune may be far more uniform and conducive to life than that of our own globe. The chilling influence of the solar stream at that planet being nearly null, and the temperature of the surrounding space far greater. So also Mercury, instead of being the burning planet of the schools, may suffer the most from cold.

The planet Mars is generally considered, of all the members of the system, most nearly to resemble our own world. The telescope not only reveals seas and continents, but the snowy circles round his poles, which appear to increase and diminish, as his winter is beginning or ending. This planet's ecliptic is similar to our own in inclination or obliquity, his distance, also, is far greater, and his winter longer; yet, for all this, his snow zones are less than on our own globe. This anomalous fact has, we believe, never been noticed before; but it is explicable on the theory, and therefore confirms it. Mars has no satellite, and therefore his centre will be coincident with the centre of the marsial vortex. There will be no lateral vortices to derange his atmosphere, and if the axis of his vortex coincides also with the axis of the planet, the central vortex will be continually over the poles, and there will be no storms on the planet Mars. A capital fact connected with this, is the want of belts, as in Jupiter and Saturn; for these planets have satellites, and if they are not massive enough, the belts may be produced by an obliquity in the axis of the Jovial and Saturnial vortices. If Mars had an aurora like the earth, it is fair to presume the telescope would ere this have shown it. He is, therefore, in equilibrium. In applying this reasoning to the earth, we perceive that a certain influence is due to the difference of temperature of the ethereal medium surrounding the earth, at perihelion and aphelion, being least at the former, and greatest at the latter.

As a modifying and interfering cause in the action of the vortices, we must mention the great natural currents of the atmosphere, due to the earth's rotation.

It is considered that the sun is the principal cause of these great currents. By elevating the surface atmosphere of the equator, a lateral current is induced from the north and south; but on account of the enlarging circles of latitude, their direction tends more from the north-east and south-east. These currents are usually called the trades. Without disputing the correctness of this, it may be doubted whether the whole effect is due to the sun. As this principle affects the ocean likewise, it is necessary to look into it; and in order to simplify the question, we will first suppose our globe covered entirely by the ocean, without any protuberant land.

Let us assign a uniform depth of ten miles to this ocean. In the Fig. following, the two circles will represent the surface and bottom of the ocean respectively. The axis of rotation is thus represented by the line PP'. Let us consider two particles of water at m and n, as feeling the influence of this rotation; they will, of course, be both urged towards the equator by the axifugal force. Now, every particle in the ocean being also urged by the same force, it might be supposed that after a protuberant mass of water had accumulated at the equator EE', the whole ocean would be in equilibrium. This would not follow. The particle at m is urged by a greater force than n; consequently the particle at n is overborne by the pressure at m. Considering both in the same direction, yet the particle at n must give way, and move in the opposite direction. Just as the heaviest scale of the balance bears up the lightest, although both gravitate towards the same point. This is so self-evident that it would seem unnecessary to dwell upon it, had not the scientific world decided that the rotation of the earth can cause no currents either in the atmosphere or in the ocean.

The axifugal forces of the two particles m and n are directly as the lines Mm and Nn, and if the gravitating forces were also as the radii Tm and Tn, no motion would be produced. Admitting even the Newtonian law to be rigidly exact, the earth cannot be considered a homogeneous globe, but, on the contrary, the density of the central parts must be nearly thirty times greater than the density of the surface of the ocean. The ratio of the gravitating forces of these two particles is, therefore, less than the ratio of their respective radii, and the axifugal tendency of the particle at n is more than proportionally restrained by the central gravitation; and hence m will move towards the equator, and n towards the poles, as represented in the Fig.

It is on account of the overwhelming momentum of the surface waters of the South Pacific over the North, that the Pacific, at Panama, stands six or seven feet higher than the Atlantic. We shall again allude to this interesting fact.

According to newspaper reports of a lecture, delivered in New York, by Lieut. Maury, U. S. N., this gentleman endeavors to explain the currents of the ocean, by referring them to evaporation in the tropics. The vapor leaves the salt of the water behind, and thus, by continual accumulation, the specific gravity of the tropical waters is greater than that of the superficial waters nearer the poles; the lighter water, therefore, passes towards the equator, and the heavier water below, towards the poles. If this be a correct statement of that gentleman's theory, fidelity to our standards compels us to question the soundness of the conclusion. The mere fact of the surface water of the ocean being lighter than that of the bottom, cannot on any known principles of science cause any movement of the surface waters towards the equator. When such an acute and practical physicist is driven, by the palpability of the fact that the polar waters are continually tending towards the equator, to seek the cause in the tropical evaporation, it shows that the dogma, which teaches that rotation can produce no motion, is unsound.

Sir John Herschel, in speaking of the solar spots, says: "We may also observe that the tranquillity of the sun's polar, as compared with his equatorial regions (if his spots be really atmospheric), cannot be accounted for by its rotation on its axis only, but must arise from some cause external to the sun, as we see the belts of Jupiter and Saturn and our trade winds arise from a cause external to these planets combining itself with their rotations, which alone (and he lays an emphasis on the word) can produce no motions when once the form of equilibrium is attained."

With respect to the origin of the solar spots, we have no disposition to question the conclusion; but, as regards the principle laid down, that rotation can produce no motions when once the form of equilibrium is attained, we must unequivocally dispute it. If our atmosphere were of uniform density, the rotation of the earth would cause no current such as we have described; with our atmosphere as it is, the result will be different. The momenta of two portions of matter are the products of their inertiae by their motions, and, in the present case, we must take the inertiae of equal spaces. A cubic inch of air at the surface, and at three miles above the surface, is as 2 to 1; but their centrifugal velocity varies only as the radii of the respective spheres, or as 1320 to 1321. In the polar regions, therefore, the momentum of the surface air preponderates, and, in this case, the surface current is towards the equator, and the upper current towards the poles. When, however, the centrifugal velocity is considerably increased in a lower latitude, and the curvature of the surface becomes more and more inclined to the direction of that resolved part of the centrifugal force, which is always from the axis, the surface layers will evince a tendency to leave the surface, and an intermingling will then take place in the space between latitude 70d and 50d, or in latitude 60d. As this layer is continually urged on in the same direction by the surface layer of latitudes above 60d, the upper layer now becomes a current setting towards the equator, and, consequently, the back current occupies the surface. Now, considering that the rarefying action of the sun is elevating the air under the equator, there must necessarily be an upper current from the equator to the poles; so that if we conceive the two currents to meet about latitude 30d, there will be a second intermingling, and the current from the poles will again occupy the surface. Thus, we regard a part of the effect of the trades to the rotation of the earth, which is the chief impelling power at the poles, as the sun is at the equator; and the latitudes 60d and 30d will be marked by some especial phenomena of temperature, and other meteorological features which do actually obtain. These would be much more marked if the irregular configuration of land and sea, the existence of mountain chains, and the different heating power of different latitudes, owing to the unequal distribution of the land, did not interfere; and the currents of the air (disregarding the deflection east and west) might then be represented by a treble link or loop, whose nodes would vary but little from latitudes 30d and 60d. As it is, it has, no doubt, its influence, although unimportant, when compared with the disturbing action of the ethereal vortices.

There is another phenomenon due to the action of the radial stream, which has given much trouble to the physicist, and which has yet never been explained. This is the horary oscillations of the atmospheric pressure which, in some countries are so regular that the time of day may be ascertained by the height of the barometer. According to Humboldt, the regularity of the ebb and flow in the torrid regions of America, is undisturbed by storms or earthquake. It is supposed that the maxima occur at 9 A.M. and 10 1/2 P.M., and the minima at 4 A.M. and 4 1/4 P.M. From the morning minimum to the morning maximum is, therefore, five hours; from the evening minimum to the evening maximum is 6 1/4 hours; from the evening maximum to the morning minimum is 5 1/2 hours, and from the morning maximum to the evening minimum is 7 1/4 hours. Again, these oscillations are greatest at the equator, and diminish with the increase of latitude.

If we suppose the earth's axis perpendicular to the plane of the vortex, and P the pole in the above figure, and SP the line joining the centre of the earth and sun, M and m will represent the points in the earth's equator where it is midday and midnight respectively. The solar stream penetrates the terral vortex; and strikes the earth's atmosphere along the lines parallel to SP. The direct effect would be to pile up the atmosphere at N and n; and therefore, were the earth at rest, the maximum would be at 6 A.M. and 6 P.M., and the minimum at midday and midnight; but the earth rotating from N towards M, carries along the accumulated atmosphere, being more sluggish in its motions than the producing cause, which cause is still exercised to force it back to N. From this cause the maximum is now found at K. For a like reason the minimum at M would be found at L, but on account of the motion of the earth being now in the same direction as the solar stream, the minimum is found still more in advance at k; so that, according to the theory, the interval between the morning maximum and the evening maximum, should be greater than the interval between the evening maximum and the morning maximum; and so it is, the first being 13 1/2 hours and the last 10 1/2 hours. The morning minimum should also be less marked than the evening minimum, and this also is a fact. The effect also should be greater in the tropics than in high latitudes, which again also obtains; being 1.32 French lines at the equator, and only 0.18 at latitude 70d. Had the earth no obliquity, the effect would be as the squares of the cosines of the latitude; but the ratio is diminished by the inclination of the axis. But there are other variations of the barometer of longer period, apparently depending on the phases of the moon, but which cannot be reconciled to the attracting power of the moon as an atmospheric tide; and Arago concluded that they were due to some special cause, of which the nature and mode of action are unknown. Perhaps this theory will obviate the difficulty, as although the central vortex comes to the meridian at the same time as the moon, its effect will be different on the inferior meridian to what it is on the superior one; whereas the moon's attraction should be the same on both. That the passage of a vortex over or near a particular place should affect the barometer, is too obvious to need explanation, and therefore we may say that the theory will explain all those varieties both small and great, which have caused so much speculation for the last fifty years.

TERRESTRIAL MAGNETISM.

In applying the theory to the magnetism of the earth, we must bear in mind that the earth is probably magnetic by induction, and not in virtue of its own specific action. The rotation of the surrounding ether, and the consequent production of a radial stream, calls the ether into motion within the earth's interior, as well as on the surface; but it does not follow that the ether shall also enter the earth at its poles and escape at its equator, for the obliquity of the vortex would interfere with this result. It is sufficient that this does occur in the terral vortex immediately surrounding the earth. From late experiments it is pretty well established that the axial direction of the needle, (and of other bodies also,) is due to peculiar internal arrangement in laminae or layers, the existence of which is favorable to the passage of the magnetic current.

According to the experiments of Dr. Tyndal, it is found that the magnetism of a body is strongest along the line of greatest density. As, therefore, the laminae of bodies may be considered planes of pressure, when these planes are suspended horizontally, the directive force is greatest, and the longest diameter of the body sets axial. On the other hand, when the body was suspended so that the laminae were vertical, the longest diameter set equatorial. Now, we know that the crust of the earth is composed of laminae, just as the piece of shale in Doctor Tyndal's experiments, and that these layers are disposed horizontally. And whatever force originally arranged the land and water on our globe, it is evident that the continents are longest from north to south, and therefore correspond to the natural direction of the magnetic force.

In consequence of the intrinsic difficulties of this question, and the mystery yet attaching to it, we may be permitted to enter a little more minutely into it, and jointly consider other questions of interest, that will enable us to refer the principal phenomena of terrestrial magnetism to our theory.

We have before adverted to the discrepancies in the earth's compression, as determined by the pendulum, and also to the uncertainty of the moon's mass, as deduced from the nutation of the earth's axis. It is also suspected that the southern hemisphere is more compressed than the northern; and other phenomena also point out the inadequacy of the law of gravitation, to account for the figure of the earth.

From the invariability of the axis of rotation, we must conclude that whatever form is the true form, it is one of equilibrium. In casting our eyes over the map of the world, we perceive that the surface is very unequally divided into land and sea; and that the land is very unequally arranged, both north and south, and east and west. If we compare the northern and southern hemisphere, we find the land to the water about 3 to 1. If we take the Pacific portion, and consider the north end of New Zealand as a centre, we can describe a great circle taking in one half the globe, which shall not include one-tenth of the whole land. Yet the average height of the remaining nine-tenths, above the level of the sea, is nearly 1,000 feet. Call this nine-tenths nearly equal to one-fourth of the whole surface, and the protuberant land in the hemisphere, opposite the South Pacific, amounts to 1/30,000 part of the whole mass of the earth, or about 1/700 of the mass of the moon. Again, the mean density of the earth is about 5 1/2--water being unity,--and the mean density of the surface land is only about half this: but three-fourths of the whole surface is water. Hence, we see that the materials of the interior of the earth must be either metallic or very compressible. To assign a metallic nucleus to the earth, is repugnant to analogy; and it is not rendered even probable by facts, as we find volcanic emissions to contain no heavier elements than the sedimentary layers. Besides, there are indications of a gradual increase of density downwards, such as would arise from the compressibility of the layers. Seeing, therefore, the equilibrium of the whole mass, and the consequent hydrostatic balance of the land in the sea,--seeing also the small compressibility of the solid portions, and the great compressibility of the fluid, the inference is legitimate that the whole is hydrostatically balanced, and that our globe is a globe of water, with an intermediate shell of land, specifically lighter than the fluid in which it is suspended. Where this shell is of great thickness, it penetrates to greater depths, and attains to greater elevations above the surface of the aqueous globe; where it is less thick, it is found below the surface, and forms the bottom of the upper ocean. Recent soundings give much greater depths to some parts of the ocean, than the most elevated land upon the globe. Captain Denham, of H. B. M. ship Herald, lately sounded in 37d south and 37d west, and found bottom at 7,706 fathoms, or about nine English miles.

As the interior portions of our globe are totally unknown, and the compressibility of water is well established, it is just as sane to consider water the most abundant element of nature, as solid land. The great question to ask is, whether there may not be other phenomena incompatible with this supposition? It is plain that the permanency of terrestrial latitudes and longitudes would be unaffected by the conditions we have supposed. Would the precession of the equinoxes be also unaffected? Mr. Hopkins has entered into such an investigation, and concludes: "Upon the whole, then, we may venture to assert that the minimum thickness of the crust of the globe, which can be deemed consistent with the observed amount of precession, cannot be less than one-fourth or one-fifth of the radius of the earth." These investigations were made on the hypothesis of the interior fluidity being caused by the fusion of the central portions of a solid globe; but it is evident that the analytical result would be the same if these central parts were water, inclosed by an irregularly-spherical shell of land. Nor would the result be affected, if we considered certain portions of the interior of this solid shell to be in a state of fusion, as no doubt is the case.

May not the uncertainty of the mass of the moon, be owing to the fact that this shell is not so rigidly compacted but that it may yield a little to external force, and thus also account for the tides in the Pacific groups, rather obeying the centrifugal force due to the orbit velocity of the earth, than the attraction of the moon?

Since the days of Hipparchus the sidereal day has not diminished by the hundredth part of a second; and, consequently, seeing that the contraction of the mass must be limited by the time of rotation, it is inferred that the earth has not lost 1/508th of one degree of heat since that time. This conclusion, sound as it is, is scarcely credible, when we reflect on the constant radiation into a space 60d below zero. Admit that the globe is a globe of water, whose average temperature is the temperature it receives from the sun, and the difficulty vanishes at once. Its diameter will be invariable, and the only effect of the cooling of the solid parts will be to immerse them deeper in the water, to change the relative level of the sea without changing its volume. This is no puerile argument when rightly considered; but there is another phenomenon which, if fairly weighed, will also conduct us to the same views.

It is now a fact uncontroverted, that the sea does actually change its level, or rather, that the elevation of continents is not only apparent but real. The whole coast of Sweden and Finland is rising at the present day at the rate of four feet in a century, while on the south a contrary effect is produced. Various hypotheses have been formed concerning this interesting fact. Yet from the indications of geology, it must have been an universal phenomenon in the early ages of the world, in order to account for the emersion of sedimentary deposits from the fluid which deposited them. May not internal fires be yet spreading, and the continents expanding instead of contracting? And may there not be an inequality in this process, so as necessarily to immerse in one direction nearly as much as to elevate in another? One fact is certain, the elements are scattering the materials of the land along its Oceanic coasts, which of itself must produce a very minute effect in disturbing the hydrostatic balance; but a more efficient agent is the earthquake and volcano.

The upheaving of tracts of land by earthquakes, as on the coast of Chili would thus be satisfactorily explained, by attributing a certain resistance due to cohesion or friction preventing a gradual change of level, but producing it suddenly by the jar of the earthquakes. May we not inquire also, whether the facility with which the earth seems moved by this destructive agent, does not point to the same solution as the irregularity of the figure of the earth?

This is a subject on which it is allowable to speculate, especially if any light can be thereby thrown on the still more mysterious source of terrestrial magnetism. It is for such a purpose that we have permitted ourselves to digress from that subject. In this connection we also may acknowledge our indebtedness to the sacred volume for the first germ of this theory of the weather.

Believing in the authenticity of the Mosaic history of the deluge, the author found it difficult to refer that event to other than natural causes, called into action by the operation of other causes, and all simultaneous with the going forth of the fiat of Omnipotence. Thus reasoning, he was led to regard the deluge as a physical phenomenon inviting solution, and as a promising exponent to the climatology of the early world. He looked upon the bow of promise, as the autograph of the Creator, the signature to a solemn bond, upon which the eye of man had never before rested. But if there was no rainbow before the deluge, there was no rain; and following up this clue, he was not only enabled to solve the problem, but also led to the true cause, which produces the principal commotions in our atmosphere.

Science boasts of being the handmaid of religion; yet there are names of note in her ranks who have labored rather to invest this phenomenon with the mantle of fable, and to force it into collision with the records graven on the rocky pages of geognosy. But the world is ever prone to be captivated by the brilliancy of misapplied talents, instead of weighing merit by its zeal in reconciling the teachings of those things which are seen, with those which are revealed.