ow 
53 : 



























The surface of the Great Plains is usuaily gently rolling, but in some 
localities buttes,* headlands, and detached masses of rock vary its 
otherwise monotonous aspect. The soil is generally alight mold, from 
10 to 15 inches in depth, resting on a bed of sand, gravel, and bowlders. 
In some places there is considerable clay mixed with the surface soil. 
In their natural condition the plains, mesas, and foot-hills are gen- 
erally covered with a short but succulent grass. Some portions pro- 
duce sage brush, among which nutritious grasses are interspersed, 
In other parts sage brush is the only growth. A comparatively small 
proportion is wholly barren. 
Plateaus.—The great plateaus upon the western flank of the mountain 
system have a mean elevation of about 7,000 feet above the level of the 
sea. They extend from southern Wyoming through western Colorado 
and eastern Utah into Arizona and New Mexico, and are there lost in 
low desert plains. 
By faults in the geologic structure, and by lines of cliffs and deep 
canyons, the various plateaus are separated one from another. Their 
general level is broken by mountains—single and in groups—buttes 
“and towering escarpments of rock. Some thirty mountain peaks, rang- 
ing in altitude from 10,900 to 12,000 feet above the sea, have here been 
noted. The few streams of the region find their way through canyons, 
the walls of which are of immense height. Aridity is the prevailing 
condition, and vegetation is dwarfed and scanty. 
Water-courses.—That the main crest of the Rocky Mountains consti- 
tutes the *‘Continental Divide” or line separating the eastern and west- 
ern water systems is known to all; that there is also a great Transverse 
Divide, forming northern and southern water systems, is not so gener- 
ally understood. Commencing in the northwestern part of Nebraska, 
the divide last named runs westward through central Wyoming to the ~ 
southern border of Yellowstone Park; thence southwestward to the 
northwestern corner of Nevada. 
Hence there are four great basins; one sloping to the northeast, 
drained by the waters of the Upper Missouri; one at the northwest, 
drained by the Columbia River; one at the southwest, which is double 
and discharges its waters into the Great Salt Lake Basin and the Colo- 
rado River; and one at the southeast, which is drained by the Arkan- 
sas and Rio Grande Rivers and their affluents. These several systems 
radiate from a common center, and have their sources in the high and 
snowy mountains of Wyoming and Colorado. The fact, however, should — 
not be overlooked, that other and surrounding parts of the Rocky 
Mountain region largely contribute to the volume of water in the prin- 
cipal streams. 3 | 
In considering further the several systems here outlined, it appears 
that at the northeast the South Platte rises in South Park and the 
- 

* Butte (Fr., pronounced bute), an isolated peak or elevation of land in the central 
and western parts of North America (too high to be called a hill or ridge, and not 

