The Rocks of the John Day Valley. 165 



Doubtless both portions of the valley were 

 once continuous and formed one lake, but a 

 stream of lava from the Blue mountains seems 

 to have run into it near the present site of 

 Camp Watson, dividing it into an upper and 

 a lower lake. The lower one seems to have 

 drained off first, the upper one remaining a 

 lake into the later Tertiary period, and receiv- 

 ing into its archives the remains of the animal 

 types of a later age. The river was apparently 

 turned northward by that outpouring of vol- 

 canic materials, and cutting for itself a new 

 channel in the deep canyon thirty miles or 

 more away formed a great bend, and exca- 

 vated an immense basin in these nearer and 

 lighter colored Tertiary rocks. Above that 

 bend, that canyon and that volcanic outflow, 

 the valley opens again, and there, extending 

 from Cottonwood creek to Canyon City, are 

 the remains of the upper lake depression of 

 the John Day valley. This later lake depres- 

 sion received into its sediment a larger amount 

 of volcanic ashes and cinders than the lower 

 one did. Several of its strata are pure vol- 



