140 GEOGRAPHIC DISTRIBUTION. 



the waves of the Uinta Sea dashed, forming deep caverns in the mural rock, 

 and then at other horizons was a retreating slope. A further study of the 

 facts shows that on a horizontal plain the projecting rocks inclosed deep bays. 

 But we must remember that as the beds were deposited denudation pro- 

 gressed ; so that the slope seen does not represent it as it existed at any 

 one time during the deposition of the beds, but only the slope which was 

 finally produced. At the beginning of the Uinta epoch it must have been 

 much steeper than it is represented in the diagram. 



About 10,000 feet of the Uinta Sandstone is found to have been de- 

 posited against the old quartzite headland before it was buried by the upper 

 members of the Uinta Group. Hence this headland must have been at 

 least 10,000 feet higii but doubtless the quartzite itself was steadily de- 



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nucled during this time, 'and we may suppose that it wasted away by erosion 

 above quite as rapidly as it was buried below. Certainly this supposition 

 is not violent ; and this would lead to the conclusion that the great headland 

 was 20,000 feet high at the time when the lowest knowji number of the 

 Uinta Sandstone was formed. We may now with some degree of probability 

 resto.re in imagination one feature of that ancient geography and see a 

 mountain more gigantic in its proportions than any which now pierces the 

 clouds floating over North America, Stand on the great plain by the Platte 

 River and look at Long's Peak; on it pile all that can be seen of Pike's 

 Peak from the banks of the Arkansas, and over these place all of Gray's 

 Peak that stands above the same plain, and the mountain thus built up in 

 imagination would not equal in altitude this quartzite mountain, whose feet 

 were bathed in the old Unita Sea. Geologists have arrived at the conclu- 

 sion that these quartzites and schistic rocks which appear over man}' portions 

 of the earth were oriinnallv accumulated as sediments and subsequently 



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metamorphosed. In the case of this group the metamorphism was anterior 

 to the deposition of the sandstones as seen from the facts mentioned above, 

 viz, that the sandstones are composed of material denned from the meta- 

 morphic group. But the sandstones have great thickness and underlie un- 

 conformably an extensive series of Carboniferous rocks. From this we infer 

 that the quartzite is of great geological antiquity. 



