WHAT THE CHEMISTRY OF THE ROCKS 

 TEACHES.* 



It is a general rule that substances can crystallize only while 

 solidifying from the liquid state of either fusion or solution. 

 The only exceptions are, that some few substances crystallize 

 directly from their vapors without passing through the inter- 

 mediate liquid form. Now the older unstratified rocks of the 

 geological formations, as the granites, are unquestionably fusible, 

 are crystalline in their structure, and are practically insoluble. 

 Therefore the evidence is conclusive that they were all at one 

 time in a molten, fluid state. 



Thus far, it would appear, geologists are agreed, since they 

 have named these formations the igneous rocks. But whether 

 the melted minerals were ever heated to a higher degree than 

 fusion that is to the condition of vaporized elements is an 

 inquiry either carefully avoided by the authorities in geology, or 

 merely mentioned as pertaining to an ingenious hypothesis which, 

 it is claimed, is unsustained by any sufficient proof. It remains 

 to be seen, however, if this theory of the original gaseous form 

 of the material elements does not follow as a necessary conse- 

 quence from the chemical constitution of the rocks themselves ; 

 and if it does not explain and bear testimony in geological and 

 cosmical sciences to such an extent as to make it absolutely 

 essential to them. 



The question here presented resolves itself into two alterna- 

 tives : Either the materials of the earth's crust were formed 

 according to chemical laws out of the simple elements preexist- 



* Published in Popular Science Monthly, April, 1874. 



