The Shoshone Island. 95 



turned aside by the upfold of this Cascade 

 barrier along the coast of Alaska. 



To say that this great upfold of the earth 

 kept on increasing in height and breadth 

 through the early and middle Tertiary times, 

 would tend to obscure the strong line of the 

 history, for it was the force that lifted this 

 Cascade dyke into the Cascade range of hills, 

 and these in turn into the Cascade range of 

 mountains. It was the epochs of these suc- 

 cessive upfolds that marked off into time pe- 

 riods the Eocene or early Tertiary, the Mio- 

 cene or middle Tertiary, and the Pliocene or 

 latest Tertiary. 



But there is still a wider view of its world 

 relations than this one of the Pacific slope; 

 for while this Cascade barrier was making a 

 geographical separation between our two is- 

 lands of the Pacific, there was an extension of 

 the Gulf of Mexico northward into what is 

 now British America, covering much of the 

 region now occupied by the Rocky mountains. 

 The same crumpling process that elevated the 

 Cascade barrier by a like process of elevation, 



