268 RELATIONS OF AIR AND WATER TO TEMPERATURE AND LIFE 



and take up what little moisture there is in these plains, to be after- 

 ward condensed and precipitated on the mountain slopes. 



From this cause the western coast of South America for the 3,000 

 miles from lower Chile to upper Ecuador is dry and barren, and would 

 be uninhabited except for the mines of gold and silver in the mouutaius 

 and the deposits of nitrates and guano along the coast and on the 

 islands. Yet the rain fall in South America is greater than in any other 

 part of the world, and more than twice as great as the rain-fall in Asia. 



NORTH AMERICA, 



The northern equatorial current, less powerful than the southern, 

 crosses the Pacific about the tropic of Cancer, where it is deflected by 

 Japan, and flows northward as the Kuroshiwo current, re-crossing the 

 Pacific in a northeasterly direction. 



The Pacific Ocean is so wide that it is doubtful if this current would 

 reach the American coast were it not for the drift caused by the wind 

 which blows across the Pacific with strong and steady force. When it 

 strikes the shores of North America it is feebler and has a lower tem- 

 perature than the Gulf Stream of the Atlantic Ocean on reaching the 

 coast of Euroije. 



The currents of wind strike the coast between the fiftieth and fifty- 

 fifth degrees of north latitude, the region of greatest rainfall, and are 

 in part deflected northward and southward by the coast range of moun- 

 tains; the remaining portion blows over the mountains and uj^ the 

 valley of the Columbia. Continual fogs and rains abound on these 

 shores, and the coasts of southern Alaska, British Columbia, Washing- 

 ton, and Oregon are covered with the densest and largest growth of 

 evergreen forest in the world. These winds prevail as far southward 

 as the latitude of San Francisco, where the southeasterly trade winds 

 commence and blow offshore, leaving southern California and the 

 western coast of Central America a zone of calms, <lry and barren. 



While the western coast of the continent is bathed by the waters of 

 the Pacific, its eastern shores are washed by the equatorial current of 

 the northern Atlantic, which flows around the West India Islands, 

 through Caribbean Sea and the Gulf of Mexico. The trade winds from 

 the Gulf of ]\Iexico water the eastern coasts of Central America and Mex- 

 ico, and impinging on the mountains of the interior are deflected toward 

 the north and east over the Southeastern States and up the Mississippi 

 Valley, where they imite with the warm winds which blow directly up 

 the valley from the Gulf of Mexico, and water the valley of the Missis- 

 sippi. The rainfall in the upper part of the valley is derived largely 

 from the Rocky Mountains, the waters of the Pacific carried by the 

 winds and deposited on the Ilocky Mountains as rain and snow, being 

 again evaporated and carried eastward to fall as rain. 



This great valley extends from Canada southward to the Gulf of 

 Mexico, and from the Rocky Mountains eastward to the Alleghauies; 



I 



