Douglass : A Geological Reconnaissance. 259 



grade. The range of mountains is not a simple one, but spurs come 

 from the main axis and extend southeastward into the plain fifteen or 

 twenty miles apart. Dr. Hayden has spoken of this en echelon 

 structure. 



This region was entirely different geologically and topographically 

 from any previously encountered and the change was sudden. The 

 mountains descend southward into foot-hills, which suddenly give way 

 to a vast arid plain. The rock is nearly all of igneous origin. Far 

 away to the southward are some scattering buttes ; beyond the plain 

 to the southeast, the high, rugged points of the Tetons pierce the sky. 



In contrast with this scene, just across the Rocky Mountain range 

 in Montana, there are many mountain ranges of various lengths, com- 

 posed of sedimentary rocks from the most ancient to the youngest, 

 but principally of Archsean and Palaeozoic age, with here and there 

 masses of eruptive rocks. These mountains form sharp ridges and 

 peaks, or rounded grassy or forested slopes, bordered by rugged, grassy, 

 wooded foot-hills, which are often composed of Mesozoic rocks. Be- 

 tween the ranges of mountains are valleys, sometimes fertile and some- 

 times semi-arid, broadening and narrowing, as they make their intricate 

 way among the mountains. These valleys are usually composed to a 

 great extent of later Tertiary deposits, which form flats and benches, and 

 sometimes weather into bad-lands. Besides these, and occupying in part 

 the older valleys, are the recent river valleys. It is a land of immensely 

 varied details of topography, a land of diversified and picturesque 

 scenery, where every turn of the road brings new scenes to view, a 

 region, the rocks, valleys, hills, bluffs and mountains of which are 

 covered with inscriptions preserving for the geologist the records of 

 its immense history, only an infinitesimal portion of which has as yet 

 been deciphered. 



The plain in Idaho is lower than the southern portion of Montana. 

 Spencer is nine hundred and twenty feet lower than Monida and three 

 hundred and seventy-three feet lower than Lima, but is nearly eight 

 hundred feet higher than Dillon. 



When one reaches the region of Camas Creek — it can hardly be 

 called a valley — the scene changes. It is more level than portions of 

 the desert, but all along this great alluvial flat are cabins, farm-houses, 

 hay-stacks, grain-stacks, and straw-stacks, showing that the soil is 

 productive, and, strange to say, crops are raised without irrigation. 

 Near the streams excellent farms and fine new buildings indicate thrift 

 and prosperity. 



