STEEP TRAILS 



Again, the mineralogical and physical char- 

 acters of the two ranges bounding the sides of 

 many of the valleys indicate that the valleys 

 were formed simply by the removal of the 

 material between the ranges. And again, the 

 rim of the general basin, where it is elevated, 

 as for example on the southwestern portion, 

 instead of being a ridge sculptured on the sides 

 like a mountain-range, is found to be com- 

 posed of many short ranges, parallel to one 

 another, and to the interior ranges, and so 

 modeled as to resemble a row of convex lenses 

 set on edge and half buried beneath a general 

 surface, without manifesting any dependence 

 upon synclinal or anticlinal axes — a series 

 of forms and relations that could have resulted 

 only from the outflow of vast basin glaciers 

 on their courses to the ocean. 



I cannot, however, present all the evidence 

 here bearing upon these interesting questions, 

 much less discuss it in all its relations. I will, 

 therefore, close this letter with a few of the 

 more important generaUzations that have 

 grown up out of the facts that I have observed. 

 First, at the beginning of the glacial period 

 the region now known as the Great Basin was 

 an elevated tableland, not furrowed as at 

 present with mountains and valleys, but com- 

 paratively bald and featureless. 



192 



