DISTRICTS OF DRY-FARM SOILS 75 
district of the dry-farming territory is located in 
the drainage basin of the 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 voleanic 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 California. 
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 
