ORIGIN OF .MASSIVE EOCKS. 165 



agents in which the ore w;is dissolved previous to its deposition was also, 

 beyond a doubt, closely connected witli tlie origin of the massive rocks. 



Hypothesis of sedimentary origin. As is WcU kuOWU, ttiaUy gCOloglstS SllppOSC 



not only granite, but all eruptive rocks, to be i)roducts of the more or less 

 complete fusion of the sedimentary strata. On this supposition there 

 would be more or less organic matter or carbon distributed throughout all 

 rocks, and this material would exercise a most important influence on sub- 

 terranean chemical reactions. While the writers referred to maintain that 

 the massive rocks, without exception, have passed through the sedimentary 

 state, all are agreed that tlie material of which they are composed must 

 have originally formed a portion of the primeval massive crust of the 

 glolje. ^lost of them are of the opinion that tliese primeval rocks are so 

 deeply biu-iod beneath their own accumulated waste as to be totally inac- 

 cessible and that we know nothing of their character. The opinion here 

 sketched in its leading features is an old one, and, though a large number 

 of leading geologists dissent from it, it has found many able defenders. 

 These seem to me to have overlooked some objections and to have general- 

 ized too broadly from certain analogies. It is difficult to understand how 

 on a globe continually affected by upheaval and subsidence the rocks un- 

 derlying the sedimentary material can ever be entirely buried. It is 

 equally difficult to imagine any means by which the primeval rocks can 

 have been reduced to a clastic state at the enormous depth called for by 

 the h}'pothesis, a depth of at least twenty miles from the surface. 



Primeval conditions. — Gcologists aud pliysiclsts are substantially agreed 

 that the earth was once an intensely heated, plastic or fluid spheroid. This 

 I Avill assume to be true. When water began to condense on the cooling 

 globe there were of course no sediments. Even as they first solidified the 

 rocks, cannot have been absolutely level, so that some portions of the 

 surface were more exposed tlian others. For the sake of simplicity in rea- 

 soning, one may first consider wdiat would have happened after the first 

 oceans formed, had there been no such thing as upheaval and subsid- 

 ence. It is clear that all the more elevated portions of the original surface 

 of the globe would have been cut down by erosive pi'ocesses and that the 

 entire globe would have been eventually covered by a shallow ocean, the 



