164 TENTH ANNUAL REPORT OF 



theory, be as miicli expected as the ordinary deposition of moisture 

 from the atmosphere. The former wouhi originate in a mechanical 

 elevation of volcanic ashes and in matter swept into the air by torna- 

 does ; the latter from simple evaporation. In the one case, the matter 

 is upheld by magneto-electric force ; in the other, by the law of diffu- 

 sion, which regulates the blending of vapors and gases, and by tem- 

 perature. A precipitation of metallic and earthy matter would hap- 

 pen on any reduction of the magnetic tension ; one of rain, hail, or 

 snow, on a fall of temperature. The materials of both originate in 

 our earth. In the one instance they are elevated but to a short dis- 

 tance from its surface, while in the other they appear to penetrate 

 beyond its farthest limits, and possibly to enter the inter-planetary 

 space ; in both cases, however, they are destined, through the opera- 

 tion of invariable laws, to return to their original repository." 



This theory, or rather hypothesis, coming as it does from one who 

 is justly entitled to high consideration, from the fact of the special 

 attention he has given to the subject of meteorites, may mislead, and 

 for this reason the objections Avhich may be advanced against it ought 

 to be stated. First, it must be proved that terrestrial volcanoes con- 

 tain all the varieties of matter found in the composition of meteoric 

 bodies. It is true that many of the substances are ejected from vol- 

 canoes, as olivine, &c., but then the principal one, nickeliferous iron, 

 has never in a single instance been found in the lava or other matter 

 coming from volcanoes, although frequently sought for. 



But the physical obstacles are a still more insuperable difSciilty in 

 the way of adopting this theory. In the first place it is considered a 

 physical impossibility for tornadoes or other currents of air to waft 

 matter, however impalpable, " beyond the farthest limits of the earth, 

 and, possibly, into interj^lanetary space." Again, if magnetic and 

 diamagnetic forces cause the particles to coalesce and form solid 

 masses, by the cessation of those forces the bodies would crumble into 

 powder. 



We pass on to a concise statement of some of the chemical objections 

 to this theory of atmospheric origin, and, if possible, they are more 

 insuperable than the last mentioned. Contemplate for a moment the 

 first meteorite described in this lecture — a mass of iron of about sixty 

 pounds of a most solid structure, highly crystalline, composed of nickel 

 and iron chemically united, containing in its centre a crystalline phos- 

 phuret of iron and nickel, and on its exterior surface a compound of 

 sulphur and iron, also in atomic proportions — and can the mind be 

 satisfied in supposing that the dust wafted from the crater of a volcano 

 into the higher regions of the atmosphere could, in a few moments of 

 time, be brought together by any known forces so as to create the body 

 in question ? However finely divided this volcanic dust might be,_it 

 can never be subdivided into atoms, a state of things that must exist 

 to form bodies in atomic proportions, where no agency is present to 

 dissolve or fuse the particles. One other objection and I have done 

 -with this hypothesis. The particles of iron and nickel supposed to be 

 ejected from the volcano must pass from the heated mouth of a crater, 

 ascend through the oxygen of the atmosphere without undergoing the 

 slightest oxydation ; for if there be any one thing which marks the 



