DISTRICTS OF DRY-FARM SOILS 75 



district of the dry-farming territory is located in 

 tire drainage l)asin of tlie Columbia River, and 

 includes Idaho and the eastern two thirds of Wash- 

 ington and Oregon. The high plains of this soil 

 district are often spoken of as the Palouse country. 

 The soils of the western part of this district are of 

 basaltic origin ; over the southern part of Idaho the 

 soils have been made from a somewhat recent lava 

 flow which in many places is only a few feet below 

 the surface. The soils of this district are generally 

 of volcanic origin and very much alike. They are 

 characterized by the properties which normally 

 belong to volcanic soils ; somewhat poor in lime, 

 but rich in potash and phosphoric acid. They 

 last well under ordinary methods of tillage. 



The Great Basin. — The third great soil district 

 is included in the Great Basin, which covers nearly 

 all of Nevada, half of Utah, and takes small portions 

 out of Idaho, Oregon, and southern CaHfornia. 

 This basin has no outlet to the sea. Its rivers empty 

 into great saline inland lakes, the chief of which is 

 the Great Salt Lake. The sizes of these interior 

 lakes are determined by the amounts of water flow- 

 ing into them and the rates of evaporation of the 

 water into the dry air of the region. 



In recent geological times, the Great Basin was 

 filled with water, forming a vast fresh-water lake 

 known as Lake Bonneville, which drained into the 

 Columbia River. During the existence of this lake 



