Earttis Rocks to Meteorites. 23V 



alogists rather than astronomers must tell us. For a long 

 time it was accepted without hesitation that these bodies 

 required great heat for their first consolidation. Their 

 resemblance to the earth's volcanic rocks was insisted on 

 by mineralogists. Professor J. Lawrence Smith in 1855 

 asserted, without reserve, that " they have all been subject 

 to a more or less prolonged igneous action corresponding to 

 that of terrestrial volcanoes." Director Haidinger, in 1861, 

 said : — " With our present knowledge of natural laws, these 

 characteristically crystalline formations could not possibly 

 have come into existence except under the action of high 

 temperature combined with powerful pressure." The like- 

 ness of these stones to the deeper igneous rocks of the earth, 

 as shown by the experiments of M. Daubi £e, strengthened 

 this conviction. 



Mr. Sorby, in 18*1*7, said : — " It appears to me that the 

 conditions under which meteorites were formed must have 

 been such that the temperature was high enough to fuse 

 stony masses into glass; the particles could exist independ- 

 ently one of the other in an incandescent atmosphere, sub- 

 ject to violent mechanical disturbances ; that the force of 

 gravitation was great enough to collect these fine particles 

 together into solid masses, and that these were in such a 

 situation that they could be metamorphosed, further broken 

 up into fragments, and again collected together." 



Now if meteorites could come into being only in a heated 

 place, then the body in which they were formed ought, it 

 would seem, to 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 meteor- 

 ites 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 



