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THE WBATHBRING OF ROCKS 



'' In the economy of the world, I can find no traces of a beginning, no 

 prospect of an end. ' ' — Hutton. 



The stability of chemical compounds is governed by prevail- 

 ing conditions. A form of combination stable under conditions 

 existing to-day may, under tbose of to-morrow, become impos- 

 sible. As was suggested in the introductory chapter, the con- 

 ditions under which the more superficial portions of the earth's 

 crust exist are ever changing, and as a result old compounds 

 are broken up and new continually formed. All over the earth 

 rocks laid down as sediments on oceanic floors have been up- 

 lifted, folded, faulted, and pushed out of place until brought 

 tinder influences as different from those under which they were 

 formed as it is possible to conceive. Molten magmas cooling sud- 

 denly on the immediate surface formed compounds in which mere 

 loss of heat was the controlling factor, but which time proves to 

 be unstable. Slow cooling, deep-seated magmas have been, and 

 are being, continually exposed by denudation, and thus brought 

 under new influences and environments. Hence a constant re- 

 adjustment is everywhere going on, which, as will be seen, is 

 manifold in its physical manifestations. As where an entire 

 building is razed to the ground, and another of quite different 

 architectural features constructed from the old materials; or 

 again, where, without change of general plan, old timbers are 

 here and there replaced by new, so here we have at work a 

 series of processes in part seemingly destructive and in part 

 constructive, but all tending toward one end. 



The firm and everlasting hills we must learn to regard as 

 neither firm nor everlasting. "Whole mountain chains of the 

 geological yesterday have disappeared from view, and as with 

 the ancient cities of the East, we read their histories only in 

 their ruins. Yet, in all this seemingly destructive process of 

 breaking down, decomposition, and erosion, there is traceable 



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