790 



METEORIC IRON METEORIC STONES. 



MKTEOKIC IRON. See Iron, Native, and Me- 

 fame Stone*. 



METEORIC STONES, or AEROLITES, are 

 solid, semi-metallic substances, which fall from the 

 atmosphere. The descent of such bodies had been 

 long reported ; but the fact was not considered au- 

 thentic till within a few years. Tin- larger stones 

 have been seen as luminous bodies moving with great 

 velocity, descending in oblique directions, and fre- 

 quently with a loud, hissing noise, resembling that 

 of a mortar shell when projected from a piece of 

 ordnance; they are sometimes surrounded with a 

 flame, tapering oft" to a narrow stream at the hinder 

 part, are heard to explode, and seen to fly in pieces. 

 Of course, these appearances have been observed 

 only in the night ; when the stones have fallen in the 

 daytime, the meteor has not been observed, but the 

 report and the shower of stones only have been no- 

 ticed. The same meteoric mass has often been seen 

 over a great extent of country ; in some instances, a 

 hundred miles in breadth, and five hundred in length, 

 which implies that they must have had a great ele- 

 vation. Indeed, from various calculations, it appears, 

 that during the time in which they are visible, their 

 perpendicular altitude is generally from twenty to a 

 hundred miles ; and their diameter has, in some in- 

 stances, been estimated to be at least half a mile. 

 Their velocity is astonishing. Though rarely visible 

 for more than a minute, yet they are seen to traverse 

 many degrees in the heavens. Their rate of motion 

 cannot, according to calculation, be generally less 

 than 300 miles in a minute. From the dimensions 

 of these moving bodies, which certainly have not 

 been overrated, since they have been known to il- 

 luminate, at once, a region of one or two hundred 

 miles in extent, we are warranted in the conclusion 

 that the stones which come to us from them, form 

 but a very small portion of their bulk, while the 

 main body holds on its way through the regions of 

 the heavens. The velocity with which the pieces 

 strike the earth is very great, frequently penetrating 

 to a considerable depth, and when taken up, they have 

 been found, in some cases, still hot, and bearing 

 evident marks of recent fusion. Such falls have 

 happened in cloudy as well as in clear weather, which 

 leads to the belief that they are wholly unconnected 

 with the state of the atmosphere. The most remark- 

 able circumstance respecting them is, that they 

 invariably resemble each other in certain easily cog- 

 nizable characters, both as respects their external 

 properties and chemical composition, so as to render 

 it possible for a mineralogist or a chemist to recog- 

 nize them with certainty, though he should have no 

 information of their origin or fall. Those specimens 

 in which earthy matter preponderates, resemble 

 pretty closely certain varieties of the trachytic rocks, 

 or ancient lavas, but they invariably contain dissemi- 

 nated through their substance, an alloy of iron and 

 nickel, which has as yet never been discovered 

 among the productions of our earth. The earthy 

 minerals of which they are composed, are feldspar, 

 olivine and aguite the former greatly preponderat- 

 ing ; and of metallic substances, besides the native 

 iron, magnetic iron pyrites is a frequent ingredient. 

 The alloy of iron and nickel often contains chrome, 

 manganese and cobalt in minute proportions. 1'his 

 alloy varies in the proportion which it bears to the 

 earthy matters, in stones which have fallen at dif- 

 ferent times : sometimes it is scarcely to be detected 

 without the aid of the microscope ; at other times it 

 forms more than one half the bulk of the stone, 

 and immense masses are found consisting entirely of 

 native iron : such masses are called meteoric iron, 

 while the expression meteoric stones is applied more 

 strictly to those in which the earthy minerals prepon- 



derate. These last are invariably coated, on the 

 i outside, with a thin, black incrustation, and have in 

 general a spherical figure, in which we often observe 

 indentations, similar to those which are presented by 

 a mass that has been impressed with the fingers. 

 These constant characters, as respects their fall, and 

 chemical and mechanical composition, indicate a com- 

 mon origin, and have given rise to a variety of hypo- 

 theses to account for their phenomena. We can only 

 hint at these hypotheses. Some attribute them to ter- 

 restrial, and others to lunar volcanoes. They have 

 again been supposed to be concretions formed in the 

 regions of our atmosphere; while others have consider- 

 ed them as small planets revolving about the sun or 

 earth, which, coming in contact with our atmosphere, 

 take fire from the resistance and friction which they 

 meet with in passing through it.* With regard to the 

 first supposition, viz. , that these stones proceed from 

 terrestrial volcanoes, it will be sufficient to observe, 

 that no remarkable eruption has been known to have 

 happened at or near the time of their fall, and that 

 such bodies have been found at the distance of some 

 thousand miles from any known volcano ; besides, 

 the immense force that would be necessary to project 

 bodies of such enormous dimensions as these meteors 

 are known to possess, far exceeds any force that we 

 can conceive of, not to notice the want of similarity 

 between meteoric stones and ordinary volcanic ex- 

 uviae. As to the theory that they proceed from 

 volcanoes in the moon, it has a greater degree of 

 probability. The same force that would project a 

 body from the moon to the earth, would not, if it 

 were exerted at the earth's surface, send the same 

 body to the distance of ten miles, in consequence of 

 the superior gravity of our planet and the density 

 of the atmosphere. It is computed that a body pro- 

 jected from a favourable spot on the moon's surface, 

 say the centre of her disk opposite the earth, with 

 a velocity about four times that commonly given to 

 a cannon ball, or 8220 feet per second, would carry 

 it beyond the centre of attraction, and consequently 

 into the sphere of the earth's activity ; whence it 

 must necessarily either fall to the surface of the earth, 

 or circulate about us as a satellite. A body so project- 

 ed from the moon to the earth, would take three clays 

 in its passage ; which is not so long but that it might 

 retain its heat, particularly as it is doubtful whether 

 in passing through a vacuum, or very attenuated 

 medium, it would be possible for the caloric to 

 escape, not to say that it might acquire a fresh accu- 

 mulation of heat, by passing through the denser parts 

 of our atmosphere. Besides, eruptions, resembling 

 those of our volcanoes, have been frequently observed 

 in the moon ; and her atmosphere is extremely rare, 

 presenting but little resistance to projected bodies. 

 This theory might perhaps be tenable if we had only 

 to account for these showers of stones which come to 

 our earth's surface ; but these, it has been seen, are 

 a very trifling part of the main masses from which 

 they descend, and which are believed to be in 

 some instances more than a mile in circumference. 

 And since it is conceived that we experience a shower 

 of these stones every few months in some part of 

 the world, it is obvious that at this rate the whole 

 mass of the moon must soon be shot away. Nor 

 this all. Among a number of bodies, thrown at : 

 dom from the moon, it is not probable, that one 

 10,OOO would have precisely that direction and that 

 rate of motion which would be requisite to cause it to 

 pass through our atmosphere, without falling to the 



