THE CONQUEST OF ARID AMERICA 



three degrees. The scientific findings are borne out by 

 the every -day testimony of individuals. Sun-strokes in 

 the arid region are practically unknown. The rainless air 

 that sweeps over the arid lands of western America is 

 necessarily dry. It neither breeds diseases nor carries 

 their germs. It is the very breath of health. The lack 

 of moisture, combined with the configuration, forbids 

 the presence of tornadoes, and the Weather Bureau has 

 absolutely no record of such a calamity west of the 

 ninety-seventh meridian. 



The superior climate of the arid West is due to funda- 

 mental conditions which differ widely from those of east- 

 ern America. Viewed from the stand-point of the broader 

 climatic effects, the eastern half of the United States is 

 one wide plain. The moisture-laden winds from lakes 

 and gulf, as from the great ocean itself, meet none but 

 insignificant barriers. But in the Far West the moun- 

 tains are the supreme factor in the making of the cli- 

 mate. The coast range stands eternal guard along the 

 margin of the sea, while a little farther inland the Sierra 

 Nevada lifts its giant peaks to intercept the clouds which 

 escape the outer barrier and to condense their moisture 

 into snow. Down the centre of the continent, from 

 Canada to Mexico, the Rocky Mountains tower far into 

 the sky, repeating upon the eastern edge of the arid 

 region the process of condensing and storing the winter's 

 rain and holding it against the summer's need. Between 

 the three great primary ranges scores of shorter ones, or 

 isolated mountain groups, reach their long arms into the 

 desert. The dryness, purity, and lightness of the at- 

 mosphere are due to this mountain topography, and to 

 the high average altitude throughout the region. It is, 



