WEST OF THE MISSISSIPPI RIVER. 779 



The average annual rainfall in the arid region is placed at 15 inches. 

 The cold mountains condense the moisture in the country adjacent, 

 thereby robbing the plains of their quota, making it fit only for graz- 

 ing, unless reclaimed by irrigation, which would make of it a produc- 

 tive agricultural country. 



Numerous rivers, including the Missouri, Columbia, and Colorado, 

 with their respective tributaries, have their head waters within the 

 State. Among the largest rivers are the North Platte, which flows 

 for a distance of several hundred miles through central and southwest- 

 ern Wyoming, the Green in the southwest, the Snake and Yellow- 

 stone in the northwest, and the Big Horn and Powder rivers in the 

 northeast. 



TEMPERATURE AND CLIMATE. 



The climate of Wyoming is healthful, mild, equable^and salubrious; 

 cool in summer and averaging warm in winter, with but few snow- 

 storms, and the stormy winds which usually accompany a fall of snow 

 prevent the complete covering of the ground. Winter grazing for live 

 stock can therefore be depended upon, and is a conspicuous. Jfeatuxe of 

 Wyoming. The remarkable wintering of live stock is owing to the 

 peculiar climatic conditions and influences. These are almost the op- 

 posite, in most respects, to those of the low-lying countries of the same 

 latitude farther east, where the soil is wet, the atmosphere heavy with 

 moisture, and the growth of vegetation rapid, coarse, and rank. Dur- 

 ing the winters in Wyoming there are more clear, sunshiny days, with 

 fewer storms and less snowfall, than in the country eastward. Besides, 

 the mountain streams remain open during the entire winter, so that 

 the stock is not deprived of drink. The clearness and dryiiess of the 

 atmosphere at all seasons of the year make the air pure and bracing, a 

 favorable condition for sheep-raising and successful breeding. This 

 important climatic advantage is favorable to the health of live stock 

 generally. 



Another significant advantage of the winter weather is the small 

 precipitation of rainfall or snow which takes place during the winter, 

 and aids in explaining, to those unfamiliar with Wyoming, how it is 

 possible for live stock to subsist on the open ranges without other food 

 supply than the native grasses. Besides, the animals are not subjected 

 to the chilling effects of rain and snow storms of the lower and more 

 humid regions. The weather is cold, but easily withstood, because of 

 the dryness of the atmosphere. On the mountains opposite conditions 

 prevail. There the heaviest precipitation occurs during the winter 

 months in the form of snow. A record of the temperature has been 

 kept at Cheyenne. For ten years the mean temperature was 59 de- 

 grees, the highest temperature about 90 degrees above, and the lowest 

 19 degrees below zero. The air may be said to be absolutely pure and 

 the climate very salubrious, conditions exceedingly favorable for stock- 

 raising. 



