34 The Two Islands. 



through other ages a ridge of elevated hills; 

 then later, one of the world's mountain won- 

 ders, the Cascade and Sierra Nevada range. 

 This new feature in the geography of our 

 western coast was destined to become the 

 great shaping force in its subsequent geology. 

 For so great a working agent, because of its 

 relation to our narrative and our consequent 

 need of frequent reference to it, we need a dis- 

 tinctive name and shall call it the "Cascade 

 Barrier." 



In its line of progress this barrier passed 

 between the islands of our story and thence- 

 forth Siskiyou and Shoshone became pro- 

 gressively different environments. 



Before the elevation of the Cascade bar- 

 rier the two islands were the only controlling 

 features of the region and the geography was 

 simple. The later multiplication of mountain 

 masses removed this feature of simplicity, and 

 yet in each case the once lone island, later a 

 mountain mass towering above extending 

 plains, retained its dominance as a feature of 

 the landscape to such an extent that the once 



