The Rocks of the John Day Valley. 175 



rest only in the path of the theologian who 

 claims a separate creation for each great type 

 of animal life, he greatly misapprehends the 

 present state of these investigations. But it was 

 no part of the plan of this article to advocate 

 any existing theory, or to start a new one 

 in this difficult field of inquiry so full today 

 of conflicting views, but rather to call atten- 

 tion to the importance of the Columbia basin 

 as a field filled to an extraordinary degree 

 with the very facts needed to throw light on 

 the question of the origin of species. 



Three great ranges of mountains and sev- 

 eral minor ones were elevated across its water 

 shed, making so many immense dams holding 

 back the waters in extensive lake depressions, 

 among which the river itself was for ages but 

 a series of connecting links. It is now almost 

 certain that these vast lake depressions con- 

 tinued from their first formation to be such, 

 until the bones of the modern horse, ox and 

 elephant were received into their sedimentary 

 deposits, thus including records covering 

 nearly the whole period of ancient mammalian 



