94 OUTLINES OF FORESTRY. 



otherwise exist both in the equatorial and in the 

 polar regions. 



2. By acting as a screen interposed between the 

 earth and the sun, and thus preventing the earth's 

 surface from becoming too rapidly heated when 

 exposed to the sun's rays, or too rapidly cooled 

 when deprived of such rays. 



"Water enters so largely into the composition of 

 both animals and plants, that its absence from any 

 section of country invariably causes such section 

 to become a desert. 



"Within certain limits, the wealth of any section 

 of country can be accurately estimated by the 

 number of inches of rain that fall in a given time 

 on its surface. This liquid wealth may be regarded 

 as a species of bank account of such section of 

 country, by which its solvency or bankruptcy may 

 be determined. 



The ocean of vapor which forms the source from 

 which the rains are derived is, therefore, of great 

 importance to the operations of nature. 



Even a hurried glance at the map of the world 

 will show that the earth's greatest expanse of water 

 surface occurs near the equatorial regions. Here, 

 also, the sun's heat is greatest. The air over the 

 equatorial regions would become too enormously 



