720 



PLUTONIC ROOKS. 



[Ch. XXXIV. 



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In the accompanying diagram (fig. 749) an attempt is made to 

 show the inverted order in which sedimentary and plutonic forma- 

 tions may occur in the earth's crust. 



The oldest plutonic rock, No. I., has been upheaved at successive 

 periods until it has "become exposed to view in a mountain-chain. 

 This protrusion of No. I. has been caused by the igneous agency 

 which produced the newer plutonic rocks Nos. II., III., and IV. 

 Part of the primary fossiliferous strata, No. 1, have also been raised 

 to the surface by the same gradual process. It will be observed that 

 the Recent strata No. 4 and the Recent granite or plutonic rock No 



