ARID REGION OF THE UNITED STATES. 



355 



rain-fall. Its northern limit is roughly shown by the 

 Qu'appelle Valley, or more accurately by an imaginary 

 line drawn from the fishing lakes to the Moose Woods. 

 North and east of this area the precipitation is consider- 

 ably greater, and supplies the valley of the main Saskat- 

 chewan, the Touchwood Hill Eange, and the Valley of 

 the Assinniboine with an abundance of moisture, which 

 is protected and treasured by forests. 



The valley of Eed Eiver east of the Little Souris, or 

 the 101st degree of longitude, receives much humidity 

 from the moist winds coining from the Gulf of Mexico 

 up the Valley of the Mississippi, and over the low height 

 of land which separates the waters of Eed Eiver from 

 those of the St. Peter. 



The Touchwood Hill Eange and the country generally 

 north of the Qu'appelle Valley, and in an easterly direction 

 towards and beyond Lake Winnipeg, are made humid by 

 the south-west Pacific wind, in concurrence with the pre- 

 vailing east wind of this region. These phenomena are 

 referred to in detail in succeeding paragraphs. 



The cause of the aridity and unfitness for settlement of 

 fully one-third of the United States, has been ably dis- 

 cussed by distinguished meteorologists. This remarkable 

 feature, extending over a portion of the American con- 

 tinent within the limits of the United States, of more 

 than 1,000,000 square miles in area, is highly important 

 in relation to the valley of the South Branch of the Sas- 

 katchewan, to a large part of which the same peculiarity 

 belongs. The physical geography of the arid region in 

 the United States has been very admirably described by 

 Dr. Joseph Henry.* 



" The general character of the soil between the Missis- 



* Meteorology in its Connexion with Agriculture, by Professor Joseph 

 Henry, Secretary of the Smithsonian Institution. 



