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It appears extremely probable that those meteors which are observed to move horizontally over extensive portions of the earth’s surface would, if watched to the end of their course, be found to terminate this by an explosion and fall ofaérolites. It is also probable that the only remaining phenomenon of analogous character, that of falling stars, which may be constantly seen to occur in the field of a large telescope, is a case of precisely the same kind—-minute cometary clouds, condensed and burnt into dust by the pressure and oxygen of the atmosphere, with the extinction of light which would follow such condensation and combustion*.
An apparent exception to the general process of attraction presents itself in the case of a few fixed stars, which are supposed to have been changed into nebula. It is more probable that no such change has occurred, and that the mistake has happened through the insuflicient power of the telescopes of early observers.
Mr. Amv’s paper gives no elucidation of that strange phenomenon, so brilliant in this climate, the zodiacal light, which by its form and position would appear to be asolar atmosphere; while we know for certain that, if all its parts have the same angular velocity of rotation as the body of the sun, no such atmosphere can extend to such a distance from the sun without being entirely carried away by its centrifugal force.
Another subject which more comprehensive views could not fail to elucidate is the TEMPERATURE of the solar system and of the medium which surrounds it.
Fourunn concludes that the temperature of the whole of the planetary space, or rather of the ether which fills it, is about 58° Fahr. But if this ether obey the universal laws of gravitation, as it is reasonable to infer from general principles must be the case, and as the contracted bulk of Encxrfs comet, near its perihelion, may be said to prove ; moreover, if, as is probable, this ether be highly mobile and obedient to the laws of latent heat, its density must be greater in th; vicinity of the sun and planets, and each atom of ether in approaching the sun or planets must have its temperature raised by the partial loss of its capacity for heat, and will again lose this heat in moving away from the sun or planets: whence it will follow that the etherial temperature must be higher in the neigh. bourhood of the larger of these bodies, and that Fous.um’s deduction concerns only that portion of the ether which immediately surrounds the earth’s atmosphere.
If we suppose the whole solar system to have been at its creation endued with the same temperature, and if we consider its members as so many liquid spheroids, subjected to the usual laws of cooling, the largest and rarest masses, and those protected by the largest atmosphere envelopes, retaining their heat the longest ; to have an explanation of the present high temperature of the sun, which with only i of the earth’s density has 300,000 times more weight, of the moderated temperature of the earth’s surface, of the ice-bound condition of the surface of the moon, which with a greater density than the earth has, only "3 of its weight, and hardly any appreciable atmosphere, and of the apparently fluid condition of the
* It is a popular belief in some parts of Great Britain that falling stars have been found in a gelatinous form upon the earth’s surface ; and from professor SILLIMAN*’S Journal, it would appear that the same notion is current in America ; the “ sparkling jelly,” there described, would form a curious subject for chemical examination I‘ From the composition of aerolites it would seem that the elementary components of the universe are the same every where, but this singular substance would appear to have no representative in our globe.
surface of Jupiter*, which with a density, and therefore a heat-conducting power, even less than those of the sun, has 300 times the earth’s weight.
Popular belief, both in ancient and in modern times, has attributed a frigorific power to the rays of the moon. Modern philosopl. ers, on the contrary, have allexpected a calorific effect from the concentration of her beams ; and an American journalist has recently published the alleged result of an experiment, in which an evident rising of the thermometer was occasioned by a powerful arrangement of this kind. Dr. Laannnn, in his monogram on heat, published in 1833, calculates on the supposition that the respective heating powers of the sun and moon's rays are in the ratio of their brightness ; that in the experiment of DE LA Hum, who condensed the lunar rays 300 times by a 3-feet burning glass, the heating effect could not have been so much as $5 of a degree. Sir J OHN Hsnscr-nan, in his work (which I have not seen) on Astronomy, also published last year, gives the following imaginary description of the lunar climate : '
“ The moon has no clouds, nor any other indications of an atmosphere ; hence its climate must be very extraordinary: the alternation being that of unmitigated and burning sunshine, fiercer than an equatorial noon, continued for a whole fortnight, and the keenest severity of frost, far exceeding that of our polar winters, for an equal time. Such a disposition of things must produce a constant transfer of whatever moisture may exist on its surface, from the point beneath the sun to that opposite, by distillation in vacua, after the manner of the little instrument called a cryophorus. The consequence must be absolute aridity below the vertical sun, constant accretion of hoar frost in the opposite region, and, perhaps, a narrow zone of running water at the borders of the enlightened hemisphere. It is possible then, that evaporation on the one hand, and condensation on the other, may to a. certain extent preserve an equilibrium of temperature, and mitigate the extreme severity of both climates.”
In this instance, popular prejudice, though also overshooting the mark, has probably erred less than philosophical hypothesis. There is no suflicient reason for believing that the moon’s temperature ever was higher than that of the earth at the same time ; and on the supposition that at some very distant period they were equal, it must follow from the greater comparatively surface of the moon, from her greater density and heat-conducting probable power, and still more, from her almost total want of an atmosphere, that her temperature on the surface is very greatly inferior to that of any portion of the earth; whence, under any circumstances,the earth must constantly give out heat to the moon, which will, therefore, with effect, appreciable or not, according to the power and sensibility of the instruments employed, act upon the thermometer like the mass of ice used by the Florentine Academicians, which gave rise to so many speculations upon the possibility of a radiation of cold. It is probable that the temperature of the moon’s surface does not exceed that of the etherial space which immediately surrounds it ; and, from the considerations above detailed, especially the moon’s smaller mass, that this falls short of the temperature determined by Foonlan as belonging to the etherial space immediately beyond the earth’s atmosphere.
* The physical condition of Jupiter’s surface, his ever-varying belts, all disposed in parallelism with his equator, and the occasional more permanent spots like the summits of icebergs floating in a liquid medium, would perhaps be best explained by the hypothesis of this planet still being in a state of partial fusion. His moons may be at alower temperature, and now inhabited.
The telescopic appearance of the moon, the snowy covering of her Phlegraen continents, and the silent ruggedness of her frozen seas, might suffice to disprove the existence of a temperature upon her surface equal or similar to that of the earth. In what respect, it may be asked, differs theaspect of the bright portion of the moon’s disc from that which would be assumed by a portion of the Himalaya mountains viewed at the distance of the moon, when winter has clothed both eminence and valley in a uniform robe of snow, and bound in icy chains every stream and expanse of water? In that elevated region of the earth there is a partial, in the moon there is nearly a total, want of that atmospheric envelope, which, like a garment, enables those bodies which receive it to retain the solar warmth. The moon’s rays will no more heat a warmer thermometer than will the concentrated light given out by a snowy range of terrestrial mountains. This refrigeration appears to have extended through a great thickness of the moon’s external crust, for her volcanoes are nearly extinct: the flames which they give out were barely visible even through Sir W.’ H1:nscmn’s powerful telescopes.
Still less compatible with their snowy whiteness, and with the bold, precipices and overhanging character of the lunar Alps, is Sir Jorm Hnnscnrm’s idea of a monthly revolution of the climate on the moon's surface. Not onlywouldthe linen terminator or boundary of light and darkness befollowed during themoon’sincreaseby a bright line of melting snow, while the enlightened face generally would present a scene of overwhelming deluges, breaking down the edges of its numerous elevated cavities, and reducing the moon’s surface to a near resemblance to that of the earth ; but the irresistible expansive force of the ice, monthly freezing in the fissures and cavities of its mountains, would in the course of a few years reduce these to a much smaller altitude than those which are now left upon the earth,
It is probable indeed, that the causes of the striking differences between the lunar and terrestial Surfaces may be referred solely to the smaller bulk and rarer atmosphere of the moon. An attentive examination of the most ancient craters of volcanoes now active, such as Vesuvius, will shew, that the first stage of a violent eruption must have been the blowing into the air an inverted conical mass of the mountain, two, three, or four miles in diameter, leaving a crater of similar dimensions, such as may yet be traced of Vesuvius, where Monte Somme forms the eastern edge of the ancient crater, upwards of four miles distant from the western, with the modern cone and crater rising between them, like the central elevations, which are to be seen in the circular hollows of the moon. From the smaller force of gravity at the moon’s surface, the masses displaced by those ex. plosions have greatly exceeded the size of any craters that can now be traced upon theearth, many of the lunar cavities being from twenty to fifty miles in diameter and a mile or two in depth. A rapid refrigeration appears to have followed the active era of the lunar volcanoes, so that the whole of them remain visible and unaltered by falls of rain or by alternate frosts and thaws, (while the operation of these causes upon the earth's surface has left barely traceable vestiges of whole volcanic re. gions ;) and, during the short period of her being a habitable world, her atmosphere must have consisted chiefly of watery vapour.
If would appear, from the known laws of the communication of heat by radiation, that the created universe is constantly suffering a loss of that principle, which can be supplied only by successive exertions of the creating power. Hence the decay and loss of old stars, and the appearance of new ones recorded in the annals of astronomy.
The instruments for 10 A. M. and 4 P. M. are suspended in the free air of the Laboratory, those for 5 .11. M. and 10 P. 111. in the south veranda of a third fig I -.
ear the cathedral. 'l‘he register thermometer for extremes is also in the same veranda. ,