744 THE POPULAR SCIENCE MONTHLY. 







have been a large one. But the comets, on the contrary, appear to have 

 become aggregated in small masses. The idea that heat was essential 

 to the production of these minerals was at first a natural one. All 

 other known rock formations are the result of processes that involved 

 water, or fire, or metamorphism. All agree that the meteorites could 

 not have been formed in the presence of water or free oxygen. What 

 conclusion was more reasonable than that heat was present in the form 

 of volcanic or of metamorphic action ? 



The more recent investigations of the meteorites and kindred stones, 

 especially the discussions of the Greenland native irons and the rocks 

 in which they were imbedded, are leading mineralogists, if I am not 

 mistaken, to modify their views. Great heat at the first consolidation 

 of the meteoric matter is not considered so essential. In a late paper 

 M. Daubree says : " It is extremely remarkable that, in spite of their 

 great tendency to a perfectly distinct crystallization, the silicate com- 

 binations which make up the meteorites are there only in the condition 

 of very small crystals all jumbled together as if they had not passed 

 through fusion. If we may look for something analogous about us, we 

 should say that instead of calling to mind the long needles of ice which 

 liquid water forms as it freezes, the fine-grained texture of meteorites 

 resembles rather that of hoar-frost and that of snow, which is due, as 

 is known, to the immediate passage of the atmospheric vapor of water 

 into the solid state." So Dr. Reusch, from the examination of the 

 Scandinavian meteorites, concludes that "there is no need to assume 

 volcanic and other processes taking place upon a large heavenly body 

 formerly existing, but which has since gone to pieces." 



The meteorites resemble the lavas and slags on the earth. These 

 lavas and slags are formed in the absence of water, and with a limited 

 supply of oxygen, and heat is present in the process. But is heat 

 necessary for the making of the meteorites ? Some crystallizations do 

 take place in the cold ; some are direct changes from gaseous to solid 

 forms. We can not in the laboratory reproduce all the conditions of 

 crystallization in the cold of space. We can not easily determine 

 whether the mere absence of oxygen will not account fully for the 

 slag-like character of the meteorite minerals. Wherever crystallization 

 can take place at all, if there are present silicon and magnesium, and 

 iron and nickel, with a limited supply of oxygen, there silicates ought 

 to be expected in abundance, and the iron and nickel in their metallic 

 form. Except for the heat, the process should be analogous to that of 

 the reduction of iron in the Bessemer cupola, where the limited supply 

 of oxygen combines with the carbon and leaves the iron free. The 

 smallness of the comets should not, then, be an objection to considering 

 the meteoric stones and irons as pieces of comets. There is no neces- 

 sity for assuming that they were parts of a large mass in order to pro- 

 vide an intensely heated birthplace. 



But, although great heat was not needed at the first formation, there 



