Part 22

It is a very remarkable fact, first noticed by Olbers, that no fossil meteoric stones have yet been discovered. If this fact be coupled with the hypothesis advanced by Olbers, in reference to the origin of the asteroidal group, we should have to date that tremendous catastrophe since the deposition of our tertiary formations, and therefore it might possibly be subsequent to the introduction of the present race into the world. May not some of the legendary myths of the ancient world as mystified by the Greeks, have for a foundation the disappearance of a former great planet from the system? The idea of the existence of seven planets is one of the oldest records of antiquity; but the earth of course would not be counted one, and therefore in after times, the sun was included to make up the number; just as the signs of the Zodiac have been explained in accordance with the seasons of far later times than we can possibly assign for the invention of this division of the heavens. Let those who have the leisure, try how far the contraction and dilation of the asteroidal orbits, to some average mean distance, will restore them to a common intersection or node, as the point of divergence of the different fragments. The question is interesting in many of its aspects, and may yet be satisfactorily answered.

The composition of aerolites may also be taken as indications of the common origin and elementary texture of the planets, whether they are independently formed or have originally pertained to a former planet; for no hypothesis of telluric or selenic origin yet advanced, can stand against the weight of evidence against it. Their fragmentary character rather favors the views of Sir David Brewster, and when we consider that they have been revolving for thousands of years with planetary velocity, and in very eccentric orbits, through the ether of space, continually scathed by the electric blast of the radial stream, their rounded angles, and black glossy crust of an apparently fused envelope, may be accounted for, without difficulty, from the non-vitrified appearance of the interior. The composition of aerolites as far as known, embrace nearly one-third of all known simple substances according to Humboldt, and are as follows: iron, nickel, cobalt, manganese, chromium, copper, arsenic, zinc, potash, soda, sulphur, phosphorus, and carbon.

The theory we have thus given of the common occurrence of shooting stars, will render a satisfactory general account of their sporadic appearance; but there are other phenomena of greater interest, viz.: the occasional recurrence of swarms of such meteors, which defy all numerical estimates, being more like a fiery rain than anything they can be compared to. The most interesting feature of this phenomena, is the apparent periodicity of their return. In the following table we have set down the most remarkable epochs mentioned by Humboldt, (and no man has devoted more attention to the subject,) as worthy of notice:

About April 22 to 25 " July 17 to 26 " August 9 to 11 " November 12 to 14 " November 27 to 29 " December 6 to 12

Besides these, he mentions two showers, from Arabian authority, in October; one in October, observed in Bohemia; one observed by himself, in the Pacific, on March 15; one February 4, just preceding the terrible earthquake of Riobamba, in 1797. The Chinese annals also contain many showers of stars, before the present era commenced. Some were in March, more in July, and others in different months. How, then, in view of these numerous dates, can we attach so much importance to the periodicity of these showers? The great shower of 1833, in the United States, on the 12th and 13th of November, brought to mind the great shower at Cumana, observed by Humboldt and Bonpland just thirty-three years before, to a day; and it must be confessed that more than ordinary displays have been seen on this date. Yet, on the strength of this, every meteoric shower is supposed to be periodical, and has resulted in a theory which becomes more complicated as the phenomenon is more observed, and can never lead to any useful and practical results. To cite the numerous instances of discrepant results, would only encumber this brief notice with facts neither interesting to the general reader, nor convincing to those who hold a contrary opinion. The author of these pages has watched for many years, and, in view of all the facts, has concluded that the doctrine of periodicity (as held by present meteorologists) is not tenable. The celebrated August shower failed, also, this year, at least in this place, as for four hours each night, on the 9th, 10th, and 11th, there were fewer bright meteors than at the close of July.

Professor Olmsted, who has paid considerable attention to the subject, has indeed attempted to connect the great November shower with the zodial light, which last he considers a nebulous body, of an elongated form, whose external portions, at this time of the year, lie across the earth's path. (See Silliman's Journal for 1837, vol. xxxiii. No. 2, p. 392.) He even gives its periods, (about six months,) the aphelion of the orbit being near the earth's orbit, and the perihelion within Mercury's. In this way he attempts to explain both phenomena; but as the zodial light is seen unchanged all the year round in tropical latitudes, it is not the kind of body supposed by Olmsted, and the theory adds nothing to our knowledge. Others have imagined rings of nebulous matter, in which all the separate parts are moving in the same orbit around the sun, with a retrograde motion, and this, with some modifications, is the current theory of the day. The principal arguments rested on, for the support of this view, are derived from the great shower of 1833, in which a common radiant point was observed, and confirmed subsequently by the radiant of other years, in the same month of November. As this point is almost tangential to the earth's orbit at this season, the earth meets the nebulous ring moving in the contrary direction, and thus confers on these meteors the necessary velocity that is thought to be demanded by observation.

Now, our theory gives a totally different explanation of the phenomenon. We contend that a retrograde motion of such a nebulous mass, is subversive of our whole theory; and we must be permitted to examine certain points, hitherto disregarded by those entertaining antagonist views. It is supposed that the meteors in 1833 fell for eight or nine hours. The orbital velocity of the earth is more than 1,000 miles per minute, and the orbital velocity of the nebulous zone must have had a similar velocity. During the nine hours of meteoric display, therefore, the earth traversed 500,000 miles of her orbit, which would give 1,000,000 miles for the depth of the nebulous stratum. But if of such vast extent, how happened it that the only part of the earth in which these were visible in great density, was the United States, or a space embraced between the latitudes of 50d and 20d north, and the longitudes 60d and 100d west, (and these are the widest limits,) comprising only 1/40 of the surface of the globe? To a calm inquirer, this difficulty seems insurmountable. The author was then in the Mediterranean, on deck the greatest part of the night,--the weather fine, and nothing unusual visible in the heavens; from other sources he has also derived similar information. Yet, were the earth then passing through a stratum of meteors 1,000,000 miles in extent, it is utterly inconceivable that other portions of the earth escaped. Much stress is also laid on the fact that these meteors in 1833, passed from east to west generally, as they ought to do, if tangential to the earth in her orbit; but on the same phenomenon occurring in 1799, when the earth was in precisely the same part of her orbit, Humboldt says distinctly, "the direction (of the meteors) was very regular from north to south." How could this possibly happen, and at the same time be moving tangentially to the orbit?

There is also another fact of importance not duly weighed in forming such a theory. In 1833 the meteors evidently differed in velocity; one class, consisting of luminous points, passed like a shower of fire with great velocity to the westward, another class were like large fire-balls with luminous trains moving with less rapidity, while a third class consisted of nebulous patches which remained stationary for a long time, and frequently emitting large streams of light. These last, at least, do not deport themselves as planetary bodies moving 2,000 miles per minute. But the fact still remains, that unusual displays have occurred about the 12th and 14th of November; and also as a general thing when there are no unusual displays, the meteors are more abundant about this time. Let us try if we can reconcile these facts with the theory of vortices.

We will first confine our remarks to the increased number of meteors about November 12th and 14th. The cosmical matter composing the zodial light, or at least the lighter parts of it, is continually driven outwards by the radial stream, just as the matter of a comet's tail is stripped from the nucleus. This matter becomes involved in the terral vortex by descending the poles, and is again passed out along the equatorial plane. The form of the zodial light, as seen edgewise, gives a lenticular form for the stratum of planetary particles composing it, and its central plane has been considered as coinciding with the plane of the sun's equator. At the orbit of the earth, this lenticular space is narrowed to a very thin stratum, but undoubtedly reaches beyond the earth's orbit with a rapidly diminishing density. As the axis of the sun is inclined about 7d to the ecliptic, and the ascending node is in the 20th degree of Gemini, the earth can only pass through the plane of the sun's equator about the 12th of December and the 12th of June. If, therefore, the central plane of the vortex coincides with the plane of the sun's equator, meteors ought to be more numerous about the dates above mentioned. But the observed times are on November 12th and 13th. Now, from actual measurements, a computation has been made by M. Houzeau, that the elements of the zodial light are materially different from those of the sun's equator. He fixes the node of the light (according to Mr. Hind) in 2d heliocentric longitude, subject to an uncertainty of 12d or 13d, and its inclination to the plane of the ecliptic, 3d 35', subject to an uncertainty of about 2d. The truth is, astronomers have argued the coincidence of the two planes from considerations connecting the zodial light with the sun's equator, as if it were a solar atmosphere; but such an atmosphere is impossible, and it is high time such measures should be taken as will lead to some certain conclusion. If in the present state of the question, we were to take the mean, we should find the node in about longitude 40d, which is the position of the earth on November 2d. But in the absence of measurements, we will assume, for the sake of argument, that the ascending node of the central plane of the vortex was, in 1833, in 50d heliocentric longitude, and consequently the earth was passing through the meteoric stratum or central plane of the zodial light, on the night of November 12th. The opposite period of the year is May 12th--a date, it is true, on which no great shower of stars is recorded, but sporadic meteors are very plentiful at that time, and what is more important to observe is, that the 11th, 12th, and 13th of May, are the three noted cold days which we have before mentioned. Thus truly indicating that the earth is then in or near the central plane of the vortex along which the radial stream is at its maximum of power at any given distance from the axis.

But the question occurs, does the node of this plane remain stationary, and is there no variation of the inclination of the axis of the solar vortex? We have found from observation, that the axis of the terral vortex is continually oscillating about a mean position by the action of the moon; and reasoning from this analogy, and the constant tendency of a material vortex to preserve a dynamical balance, the same tendency must obtain in the solar vortex under the action of the great planets, whose orbits do not coincide with the central plane of the vortex. The ascending node of Jupiter's orbit is in longitude 98d, Saturn's 112d, Uranus' 72d, Neptune's 131d; so that this plane does not correspond with the plane of greatest inertia discovered by La Place, and from the non-coincidence of these planes with the central plane of the vortex, must produce the same oscillation in the axis of the solar vortex, as the moon does in the terral vortex, but to what amount, observation can alone determine. Jupiter and Saturn will of course exert the greatest influence, and when these two planets are in conjunction, the ascending node of the central plane of the vortex will vary in longitude perhaps sufficiently to bring the meteoric maximum at the ascending node into October on the one hand, and to the close of November on the other, and at the descending node to April 25th on the one hand, and the close of May on the other.

The great showers of stars which have been recorded, must be therefore considered as an accidental exaggeration of a perennial phenomenon, attaining its maximum when the earth passes through the central plane of the vortex, whose ascending node in 1833 we will suppose was in longitude 50d. This theory will therefore account for those great showers which have occurred about the 24th of April, as well as those occurring in October and November; for it is far more consonant to all analogy, to suppose the influx of planetary atoms into the solar vortex to be in irregular, than in regular quantities. Yet, whether in the one case or in the other, the matter will pass along the central plane of the vortex, either diffusely scattered or in denser clouds, and will be encountered by the earth when near the nodes more frequently than at other times. The phenomenon of 1833, may then be attributed to the earth encountering an unformed comet on the 12th of November; but we must reflect, that the medium of the vortex is also in motion, and the cometary matter drifting along with it; and that this motion corresponds with the earth's motion. By becoming involved in the terral vortex, it will in a measure be carried along with the earth in her orbit as a temporary occupant of the terral vortex. But we are here met with the objection that the radiant being nearly stationary amongst the stars, demonstrated conclusively, that the source of these meteors did not partake of the earth's motion. There is no difficulty in this. We suppose as a general thing, that the meteors descended to the surface of our atmosphere down the axis of the vortex (at least in the greatest numbers), and the geocentric longitude of this axis was nearly the same during the whole time of the display. We say nearly, for the motion of the moon in her orbit in nine hours, would change the longitude of the axis three or four degrees, and this is about the change in the position of the radiant noted at the time. This objection, therefore, falls to the ground; for the axis of the vortex, although carried along with the earth in her orbit, was unaffected by the earth's rotation, and would therefore appear nearly as stationary in the heavens as Gamma Leonis. But it is again urged, that the moon was near conjunction with the sun, and consequently the central vortex was on the opposite side of the globe. This is true; but the outer vortex must have been near the meridian about three hours after midnight, or about the time when the radiant was vertical and the display the greatest. When the axis was to the eastward, the stars would shoot westward, when on the meridian, they would pass in all directions, but principally to the south, on account of the inclination of the axis of the vortex; but this would only be true for places situated to the southward of the central latitude. During the great shower of stars seen by Humboldt, in Cumana, the direction was to the south uniformly. Now, the latitude of Cumana is above 10d north, yet still too low for the general limits of the vortices; but from the same inclination of the axis (from 30d to 36d to the surface), the meteors would pass far south of the limit, and might even reach to the equator. The latitude of the outer vortex ascending on November 12th, must have been near the line of greatest display, from the position of the moon at the time. We thus see why the phenomenon was limited to so small a fraction of the earth's surface; why these meteors should be intermingled with nebulous patches stationary in the heavens for an hour together, and why, notwithstanding these facts, they were independent of the earth's rotation.

We have yet another objection to answer, viz.: the planetary velocity of some of these bodies. Let us be understood. The velocity of a solid aerolite is due to gravitation, and is planetary, on the other hand, voluminous collections of cometary dust united by accident, and remaining so by mere inertia, are borne passively on the ethereal currents with electric velocity, and probably never penetrate far, even into the attenuated atmosphere, which may be supposed (from the facts connected with the aurora) to extend far above the denser stratum which refracts and reflects light, and from which the assigned limits of our atmosphere have been derived.

It is generally considered that sporadic meteors are more numerous in the summer and autumn than in the winter and spring, and we have, likewise, in the tenth of August, a date which corresponds to many great displays and meteoric showers, both in recent and remote times. This would seem to vitiate our theory; for we cannot suppose that there are two central planes in the vortex intersecting the ecliptic in longitude 320d and 50d. We must remember, however, that as these great displays are accidental, and as the stratum composing the zodial light is manifestly of sufficient thickness to envelope the whole orbit of the earth, that it does not necessarily follow that the dense portions to which meteoric showers are due, should be always confined to the central plane of the vortex. And, besides, we have similar displays recorded in other months, which invalidates the theory of a regularly-recurring phenomenon. We shall, therefore, only aim at explaining why meteors are generally more abundant in summer and autumn than in the opposite seasons.

The axis of the solar vortex, considered as cylindrical, must be admitted to run out to a great depth on either side from the sun, and reach far into that unoccupied space intervening between our system and the nearest fixed stars, and from these opposite points the solar vortex is supplied with that stream of ether which passes down either pole to restore a partial equilibrium in the density of the ether of the vortex, rarefied by centrifugal force. As certain portions of the heavens are crowded with stars, and other parts comparatively vacant, we may expect a similar inequality in the distribution of that cometic dust, which causes a certain amount of extinction in the light of the stars, and, therefore, seeing that the two extremities of the axis of the solar vortex are so widely separated, it would not be wonderful if different quantities of such matter were brought down into the vortex from these extremities.

From recent observations made by H. R. Birt, at the observatory of the British Association, it would appear that the brightest portion of the zodial light is always north of the ecliptic. Others have also remarked the same, and if we couple this fact with the suggestion just made, we are justified in suspecting that a greater quantity of cometic dust comes down the northern pole of the vortex than down the southern. This matter, in passing outward, does not, of course, immediately attain to the central plane of the vortex, but is more thickly distributed along a plane parallel to this plane. And the same will be observed by that matter coming down the southern pole; it will be, in a certain degree, retained in a plane south of the central plane, but still parallel with it. This would account for the greater brightness of the northern side of the zodial light. It would, also, account for the greater frequency of meteors in summer and autumn than in the opposite seasons. From May to November the earth is above the central plane of the vortex, and, consequently, on the northern side; but after passing the node in November, she is on the under or southern side, and the meteors are less frequent. With this general explanation we shall close. If what we have advanced be an approximation to the truth, the theory itself affords ample indications of what observations are requisite to prove or disprove it; and, on this account, a theory is of great benefit, as suggestive of many questions and combinations of facts which otherwise might never be thought of.

We have thus taken a cursory glance at the prominent physical phenomena of the world, and attempted to link them together in the bonds of one all-pervading principle. We have fearlessly taken a new path, and claim originality for the whole, disclaiming all intention of retailing second-hand wares, or of compiling an ingenious theory from heterogeneous scraps. If it be true, or if it be partially true, let those professionally engaged in such pursuits enter the wide field of investigation we have discovered for them; for if the whole theory be true, it only shows in a clearer light that the great work which has been fancied so near completion is scarcely yet begun; while the prospect of an ultimate and final completion of the temple which so many zealous votaries are erecting, is rendered mournfully hopeless by the contemplation of what yet remains to be performed.

FOOTNOTES:

The orbit this year was determined under very unfavorable circumstances.

According to other tables, this angle would be much greater than is given in Mr. Hind's catalogue.

Prin. Prop. xx Lib. Sec.

With reference to the resisting power of the atoms.

Prin. Lib. Tor. Prop, xxxix., also Prop, xli.

In making this suggestion, the author is well aware that Ephemerides of the four chief asteroids have been given annually in the Greenwich Nautical Almanac; but for the object proposed they are utterly useless. Will any astronomer contend that these Ephemerides are true to ten seconds of arc? If not, they are useless for the purpose suggested above, and the theory wants revision. And it is evident that any objection against its practicability, founded on the uncertainty of the number of the asteroids themselves, as has already been urged in answer to this suggestion, is an evidence that the objector weighed the subject in the scales of his imagination only.

SECTION SIXTH.

THE POLAR ICE.

We shall conclude these pages by again referring to our theory of the weather, in connection with an event which every friend of humanity and every lover of natural science is bound deeply to deplore.

From the present position of the lunar nodes and apogee, the vortices of our earth do not ascend into very high latitudes. Now, according to the principles laid down, the frequency of storms tends to lower the temperature in the warm regions of the earth, and to elevate it in the polar regions. Let us suppose the northern limit of the vortices to be in latitude 70d. There will be, in this case, a greater prevalence of northerly winds within this circle of latitude, to supply the drain to the southward, and the back currents by passing above will descend at the pole, partaking of the temperature due to that elevation. The character of the arctic seasons may therefore be considered as partly dependent on the average direction of the wind. Suppose again, the extreme limits of the vortices to be about latitude 80d, the relative areas of the two circles are as 4 to 1; so that in this last case the exclusive range of the northerly winds is limited to one-fourth of the first area. South of 80d the wind will frequently come from the south, and by mixing with the local atmosphere of that latitude, will tend to ameliorate the small area to the northward. And the greater atmospheric commotion when confined to such a small circle of latitude, must assist materially to break up the polar ice; which would tend still more to equalize the temperature.

By referring to our table, we see that the mean conjunction of the pole of the lunar orbit and the moon's apogee, was in longitude 128d on April 10, 1846, and let it be remembered that when the conjunction takes place due south or in longitude 270d, the vortices attain their greatest latitude north. When, on the contrary, the conjunction takes place due north or in longitude 90d, the northern limits of the vortices are then in the lowest latitude possible.