102 Introduction to Life of the Lakes. 



Tertiary lakes, both forming to-day the west- 

 ern slope of what was once our Shoshone is- 

 land. We find, then, in Eastern Oregon of 

 to-day the remains of several old lake beds 

 preserving a more or less complete record of 

 the life of the Shoshone region in early Ter- 

 tiary times. It is to be understood here that 

 in all that is said of lake records there is im- 

 plied a sediment of mud containing casts and 

 impressions of the living things of other ages, 

 of things as real as the writing on Chaldean 

 pottery or hieroglyphics upon a piece of 

 Egyptian papyrus. The sediments of these 

 lakes are in effect so many openings into the 

 past, openings from which the curtains of 

 time are drawn aside so we see through them 

 the vista of the ages. 



Two of these lake beds are of special im- 

 portance to us because they represent dis- 

 tinctly separate life records, the lower and 

 older one containing a marvelous wealth of 

 fossil life running through a long stretch of 

 geological history. The upper or later sedi- 

 ments are of more restricted surface but of 



