Aerolites and meteoric iron are not the only products of meteors which have fallen upon the earth after explosion. Numerous instances are mentioned of black and red dust, which has covered great tracts of land; and it is remarkable that such dust has generally been found to contain small angular grains resembling augite. There have also been cases of the fall of a soft gelatinous matter of a red colour like coagulated blood, which have given rise to the stories of the sky having rained blood. Such appearances have not unfrequently accompanied the fall of stones. On the 15th November, 1775, rain of a red colour fell around Ulm and the Lake of Constance, and on the same day in Russia and Sweden. The red water was of an acid taste, probably from the presence of sulphuric acid ; and the precipitate, which was flaky like snow, when dried, was attracted by the magnet. In the night of the 5th March, 1803, a red dust, in some places accompanied by rain, fell in different parts of Italy. In Apulia, there was first a very high wind with much noise, and then a reddish-black cloud appeared coming from the south-east, from which there fell a yellowish-red rain, and afterwards a quantity of red dust. It continued the whole of the following day and part of the succeeding ; the dust was examined, and was not found to be volcanic. Fabroni, in the 'Annales de Chimie,' torn. lxxxiii, says, that near Arezzo, in March, 1813, the ground being then covered with snow, there was a shower of fresh snow of a red colour, which continued for many hours, accompanied the whole time with a sound like that of the violent dashing of waves at a distance ; the greatest fall was accom panied with two or three explosions like thunder. The red snow being melted, a precipitate was obtained of a nankeen colour, which yielded silica, lime, alumina, iron, and manganese.
The origin of this remarkable class of natural phenomena is involved in great obscurity, and many different theories have been proposed to account for them. By some they have been supposed to be bodies ejected from distant volcanoes belonging to our earth,—a conjecture which is refuted by every circumstance connected with them. No substance in the least resembling aerolites has ever been found in or near any volcano ; they fall from a height to which no volcano can be supposed to have projected them, far less to have given them the horizontal direction in which meteors invariably move for a considerable part of their course. Another hypothesis is, that
meteoric bodies are formed in the atmosphere, which is equally untenable ; for, in the first place, there is no ground for supposing, from any discoveries yet made in chemistry, that the elements of which they are composed exist in the atmosphere ; and even if they did, the enormity of the volume of the atmosphere, attenuated as it is at the great height from which the meteors fall, which would be required to produce a solid mass of iron of thirteen tons weight, places the conjecture beyond all credibility. A third hypothesis is, that they are bodies thrown out by the volcanoes which are known to exist in the moon, with such force as to bring them within the sphere of the earth's attraction. This hypothesis was so far entertained by Laplace, that he calculated the degree of lunar volcanic force that would be necessary for this purpose. He calculated that a body projected from the moon with a velocity of 7771 feet in the first second would reach our earth in about two days and a half; but Olbers and other astronomers are of opinion that the velocity of the meteors, which has been estimated in some cases to be at first equal to some miles in a second, is too great to admit of the possibility of their having come from the moon. The theory which is most consistent with all known facts and laws of nature is that proposed by Chladni, namely, that the meteors are bodies moving in space, either accumulations of matter as originally created, or fragments separated from a larger mass of a similar nature. This opinion has also been advanced by 'Sir Humphrey Davy, at the conclusion of one of his I papers in the 'Phileeophical Transactions' for 1817, giving an account of his rest/trace on flame. It is also the opinion of Sir John Herschel and Alexander von Humboldt; the latter of whom, hi his 'Cosmos,' devotes a large space to the consideration of this highly interesting subject.
Those who wish to investigate this curious subject will find it most ably and copiously treated m Chladni' work, Ceder Fewer,Ileteore, rad aGer die mit denselbem ha-atgefallenen Masses, Vienna, 1819, which in a second edition of his first treatise. The Litholvie Atnsos 'Ater-lilac of [earn may also be consulted ; also a good compilation by Bigot de Moroguca, entitled Memoire Ilistorique t1 Physique sue Ira Chita des Pierres, Orleans, 1812; Ilumboldt's Cosmos; and tho Quarterly &eine for December, 1852.