172 The Rocks of the John Day Valley. 



surface capable of changing all to stone that 

 they touched. 



The mammoth, the horse and the ox ap- 

 pear in the light of the dawn that follows this 

 long geological night, and not fire, as before, 

 but frost, seems to have closed the record 

 marked by their fossil remains. 



This alternating of light of life and dark- 

 ness of death as read in the rocks of that 

 region leaves us long periods of its chronology 

 unwritten save by fire and flood. What are 

 these blanks in that life-record? Have the 

 materials upon which they were originally 

 written been partially or wholly destroyed or 

 washed away? No, for in a neighboring 

 mountain, fifteen hundred feet in vertical sec- 

 tion, they still remain, protected by a heavy 

 capping of basalt. The pages are there but 

 they are defaced by fire and ashes. But were 

 there not, or at least might there not have 

 been, vast periods during which no record 

 was made? 



This supposition, too, is inadmissible. A 

 lake existed here through the whole Tertiary 



