209 



their way flirectly tbrou^-b moaiitaiii-range8 instead of foUowliiK synclinal denressionK 

 iSe'eW^tiofnf'tr" ''"f'^ the process of erosiou at the time of"th'e co";?>encEnt 

 the elevatKHi of the surface. This is shown all alon- the valley of the Yellowstouo and 

 more conspicuously in the valleys of the Madison and Gallatin, which have carved tm 

 mense canons or gor-es directly through two of the loftiest ranges of mountains in 



?W nfti r ' ^^"^' *^'"^ *^ '•'?'^" "^ *^^«« '^'^■^"'' ^^« "^^^ked out at or near the 

 f ^7^ . i ■ <^'^«*^««o»s period ; and as the ranges of mountains were in process of elcvn- 

 t on to their present height, the erosiou of the channels continued. The details of the 

 observations which contributed to form this opinion would occupy a chapter or two. 



I would be glad to find the leisure at some future period to extend these 

 observations m detail all over the country west of the Mississippi, so far as 

 It has been explored. It should be done by some one; but as these notes 

 are intended simply to convey brief descriptions of the sections accompa- 

 nying them, It cannot be done at this time. The sections, however, 

 will, i think, be acknowledged by all geologists and geographers to 

 convey marvelously true pictures of the surface features of a remarkablv 

 interesting region. 



