132 Life of Upper Lake Region. 



snow, heat and frost began a new structural 

 surface and continued its reshapings until a 

 drainage system was worked out for another 

 geological period. How long this period of 

 reconstruction lasted is not recorded; its very 

 stages of progress have long since been 

 blotted out. For aught the record would in- 

 dicate it may have lasted as long as the whole 

 time of the lower lake history, and through- 

 out this whole reconstruction period the hills 

 and plains of Shoshone may have richly 

 abounded in mammalian life, only lacking 

 nature's mode of recording the life of the hills, 

 a good deep lake bed into which mountain 

 streams might in time wash their life remains. 

 The new lake period at length opens as 

 a result of these reconstruction changes. The 

 old Shoshone lake had covered a large part 

 of what is now Eastern Oregon; the new lake 

 system consisted of a number of more re- 

 stricted bodies of water. One of these, the 

 earliest published, may be found along the 

 upper John Day valley, beginning where Cot- 

 tonwood creek joins the John Day river and 



