CORDILLERAN MESOZOIC RE VOL UTION. 5 8 1 



hundred miles. In the portion examined there are several masses 

 or belts of schistose metamorphic rocks which have been sunk 

 down into the granite, but they form a small proportion of the 

 entire complex. The granite varies somewhat in_ mineralogical 

 composition, texture, and structure, and is often distinctly gneissic 

 locally. In places it is essentially hornblendic, in others it is 

 micaceous. Notwithstanding these variations, which are com- 

 mon in most large granite masses, the granite seems to be a unit 

 throughout, and the mass is certainly a very important factor in 

 the epeirogeny of the west coast of America. Even should it be 

 discovered by the closer scrutiny which science will certainly 

 demand, that there are portions of an older granite terrane to be 

 discriminated from the general mass, the conclusion will not be 

 invalidated, that in the interval between the deposition of Trias- 

 sic strata and the deposition of lower Cretaceous, the earth's 

 crust was in this region invaded by an immense batholitic magma, 

 hundreds of miles in extent, which absorbed a large part of the 

 pre-Triassic basement, as well as a portion of the Triassic rocks 

 themselves. This invasion of the crust by the British Colum- 

 bian batholite seems to have conditioned a general and pro- 

 nounced elevation of the coast. For the erosion which intervened 

 before the deposition of the Cretaceous was possessed of a vigor 

 only born of lofty mountains, removing the upper crust and cut- 

 ting down deep into the congealed granite. The Cretaceous 

 rocks were littoral deposits at the base of these lofty mountains. 

 Thus was a great revolution wrought in the geology and physi- 

 ography of the west coast of British Columbia in the interval 

 between the Triassic and Cretaceous times. 



Little is definitely known of the geology of the Olympic 

 Mountains, but it is probable that the conditions which prevail 

 on Vancouver Island, which is the northern extension of the 

 range, hold good here, the Cretaceous rocks of the coast repos- 

 ing upon the lower flanks of mountains which consist of a com- 

 plex of granite and metamorphic rocks. These mountains are 

 probably the least known portion of the United States, and they 

 are mentioned here simply to indicate that important evidence 



