CLIMATE. 47 



The desert of Atacama, between Chili and Peru, the semi-desert 

 of California, the desert of Sahara, and the arid plains of Australia 

 lie in these latitudes. The aridity on the North American coast is 

 felt even beyond Oregon through half the year. The snowy peak 

 of Mount St. Helen's, 16,000 feet high, in latitude 43°, stands for 

 weeks together without a cloud. The region of the Sacramento 

 has rain ordinarily only during three or four months of the year. 



As the first high lands struck by moist winds usually take away the 

 moisture, these winds afterwards have little or none for the lands 

 beyond. Here is the second great source of desert-regions. For 

 this reason, the region of the eastern Rocky Mountain slope, and 

 the summits of these mountains, are dry and barren ; and, on the 

 same principle, an island like Hawaii has its wet side and its 

 excessively dry side. 



Under the influence of the two causes, Sahara is continued in an 

 arid country across from Africa, over Arabia and Persia, to Mon- 

 golia or the Desert of Gobi, in central Asia. 



It is well for America that her great mountains stand in the far 

 west, instead of on her eastern borders to intercept the atmospheric 

 moisture and pour it immediately back into the ocean. The waters 

 of the great Gulf of Mexico (which has almost the area of the 

 United States east of the Mississippi), and those of the Mediterra- 

 nean, are a provision against drought for the continents adjoining. 

 It is bad for Africa that her loftiest mountains are on her eastern 

 border. 



It is thus seen that prairies, forest-regions, and deserts are 

 located by the winds and temperature in connection with the 

 general configuration of the land. 



49. The movements of the atmosphere and ocean's waters, and 

 the surface-arrangements of heat and cold, drought and moisture, 

 sand-plains and verdure, have a comprehensive disposing cause in 

 the simple rotation of the earth. Besides giving an east and west to 

 the globe, and zones from the poles to the equator, this rotation 

 has made an east and west to the atmospheric and oceanic move- 

 ments, and thence to the continents, causing the eastern borders of 

 the oceans and land to differ in various ways from the western, 

 and producing corresponding peculiarities over their broad surface. 

 The continents, though in nearly the same latitudes on the same 

 sphere, have thence derived many of those diversities of climate and 

 surface which, through all epochs to the present, have impressed 

 on each an individual character, — an individuality apparent even 

 in its plants and animals. The study of the existing Fauna and 

 Flora of the earth brings out this distinctive character of each 



