74 • DESCRIPTIVE GEOLOGY. 



line of the railroad, has an elevation of 7,143 feet, or a little more than 

 1,000 feet above Cheyenne, near the east base of the Colorado Range. The 

 surface of the country is undulating, with slopes so gentle, and with such 

 rounded outlines, that to the eye the greater part of the area seems 

 practically level, and appears only to be broken by long bench-like ridges 

 and occasional patches of sandstone, which have escaped the general 

 erosion. Over the greater part of the area there is no elevation that could 

 possibly be called a mountain or butte, only hilly ridges 100 or 200 feet 

 above the general level. 



The Laramie Plains are drained almost exclusively by the Laramie 

 River, which, rising high iip in the Medicine Bow Range, enters the plains 

 near Sheep Mountain, floAVS a little north of east until it reaches the lowest 

 part of the valley on the eastern side, then near Fort Sanders turns and 

 runs north, with a very circuitous course, till beyond the limits of our map. 

 No stream joins the river from the east, and from the south only two creeks, 

 Willow and Antelope, reach the main stream. Numerous streams come 

 down from the Medicine Bow Range on the west, but the Little Laramie, 

 with its many tributaries, alone empties into the main river, the others 

 either ending in lakes or sinking in sands, except in seasons of long- con- 

 tinued rains. The Laramie River is a fine, clear stream, with a rapid cur- 

 rent and a broad alluvial bottom covered with grass. 



Rock Creek, at the northern end of the Medicine Bow Range, after 

 running out upon the plain, suddenly turns, flows westward around the 

 Como ridge, and joins the Medicine Bow River; the only stream that does 

 not drain toward the Laramie River. 



Dotted over the surface of the plain occur numerous small lakes, lying 

 in shallow basins in the nearly horizontal sandstones. Many of them are 

 fresh-water lakes, or only slightly brackish; while others, especially the 

 smaller ones, are strongly alkaline, and, in dry seasons, completely disap- 

 pear, leaving incrustations of salines, admixtures of carbonates and sul- 

 phates. Deposits of these salts also occur on the plains, which may prove 

 to be of considerable thickness and of , economic value. The largest of the 

 lakes is known as Cooper's Lake, lying in about the middle of the plains, just 

 west of the railroad. It measures nearly 4 miles in length by 2 in width. 



