96 The Shoshone Island. 



closed this American Mediterranean to the 

 ocean, and also added to the height and 

 breadth of the already begun upfold of the 

 Rocky mountains. This change was closely 

 followed by the conversion of the inclosed 

 waters of the region from salt, through brack- 

 ish, to fresh waters. 



And yet a still wider relationship may be 

 mentioned. Up to the time when the Cascade 

 barrier was separating our Pacific islands, 

 Western Europe, from the British islands to 

 the Black sea, was covered by a deep ocean 

 over whose bed had been slowly deposited the 

 cast off calcareous shells of a Protozoan ani- 

 mal, the Globigerina. This accumulation of 

 life-remains, hundreds of feet in thickness and 

 extending over a length of six hundred miles, 

 was brought to a close by the elevation of the 

 sea bed, its calcareous sediment to be known 

 in after time as the chalk beds of Europe. 



Now this shrinking and the resulting 

 crumpling of the surface seen in this light, be- 

 comes a world fact; its manifestation in the 

 Cascade barrier, its other manifestation along 



