13 



earlier on the table-lands. Often it is a difficult matter to get water 

 for irrigation upon these benches, and farmers must depend upon the 

 snow and rain for the supply of moisture for their crops. Along some 

 of the streams, as in the case of the Big Horn Eiver in Wyoming, 

 there are no benches or terraces, the valley being limited by high, 

 abrupt bluffs leading to the uplands which rise gradually to the foot- 

 hills and mountains. 



Extending to the eastward from the principal ranges of the Conti- 

 nental Divide are the vast stretches of level plain, rolling prairie, and 

 rough, eroded bad lands, constituting the great range region east of 

 the Eocky Mountains. Over a considerable portion of this region 

 rugged buttes are scattered here and there in addition to the previously 

 mentioned outlying mountains, relieving the monotony of prairie and 

 plain and affording welcome landmarks for the cowboy and traveler. 

 Occasionally considerable portions of the plains area are cut off" from 

 the remainder by natural barriers of hills and mountain ranges, form- 

 ing drainage basins of considerable extent, as in the case of the Judith 

 basin, in Montana, and the Big Horn basin and the Laramie plains, in 

 Wyoming. 



THE SOIL. 



The character of the soil in the eastern Eocky Mountain region is 

 exceedingly varied. According to Prof. W. C. Knight, "the various 

 geological formations which have entered into the soils of Wyoming 

 range from Archiean to the Pliocene Tertiary," and the great variability 

 in the composition of the different soils is readily explained from the 

 fact that "some of them have been derived from the entire series of 

 rocks ranging from the Archaean to the close of the Tertiary, while 

 others are the result of the decaying of a single geological horizon." 

 These statements are essentially true of ^Montana and Colorado. The 

 soil in the valleys varies from light sandy loam to a heavy black loam 

 or a stiff clay. Sometimes a great deal of gravel is present, and 

 often, particularly in the higher valleys, the surface is strewn with 

 bowlders of various sizes brought down by glaciers or mountain tor- 

 rents. These bowlders are particularly abundant In the valleys of 

 some of the streams rising in the Big Horn, Shoshone, and Medicine 

 Bow mountains, often rendering it practically impossil)le to drive 

 through with a wagon. The ranchers assert that when the land is 

 brought under irrigation these bowlders gradually work into the soil 

 and in a few years all the smaller ones disap])ear beneath the surface, 

 making it possible to use the land for hay meadows. The soil is 

 usually fertile and gives excellent yields of grass. In many places 

 the clay contains quantities of "alkali" and constitutes the so-called 

 "gumbo" and "adobe" soils. The soil of the foothills and mesas is 

 usually quite sandy or gravelly, and is warmer, and hence earlier, than 

 the heavier soil of the valleys. On the prairies and plains the soil 

 varies from a sandy to a clay loam, in some places thick and well sup- 



