1 76 The Rocks of the John Day Valley. 



life upon the earth. Add to these facts that 

 all the rocks through which the streams of 

 this region during this long geological period 

 have been wearing their way were those of 

 the later and softer materials, and therefore, 

 the more rapidly worn down, not only in the 

 canyons of the larger streams but the ravines 

 of the smaller ones and upon every hill side, 

 and we have a combination of favoring condi- 

 tions such as must make its geology accessi- 

 ble, very full and important. 



Indeed, one can hardly look over its his- 

 toric archives of the Tertiary period without 

 a conviction that this Columbia basin is des- 

 tined yet to be the great battle ground of 

 conflicting theories upon the question of the 

 origin of species. 



