Life of Upper Lake Region. 131 



But more. This great lake bed, one hundred 

 miles or more across, was slowly and unevenly 

 elevated, till, in some places, its bed was 

 tilted to an angle of several degrees from 

 its original level. It was slowly emptied of 

 its covering of water till an extended val- 

 ley only remained to mark its outline, but 

 the Miocene lake had gone forever. The 

 tiltings of the bed of the old lake, its 

 foldings and crumpled condition, give strik- 

 ing evidence of the great forces that mark 

 its passing away. Another fact of like im- 

 port calls for a word of notice, the occur- 

 rence at irregular intervals of dykes of trap 

 showing masses of lava that were forced up 

 from below, filling great orifices in, the hard- 

 ened mud of the lake bed and speaking of 

 nothing if not of force and heat. It was in 

 this cloud of confused and struggling forces 

 that the old Miocene record closes. 



All that is now Eastern Oregon then be- 

 gan a new series of changes on the surface 

 of the upturned ruins of hill and vale. And 

 upon this uptilted mass of confusion, rain and 



