WHAT THE TREES ARE 5 



If you were to keep the glasses going, no doubt 

 the one containing the cuttings would throw off 

 gallons of water, before a single gill would evap- 

 orate from the other glass. So you see that the 

 proportion of moisture exhaled from any given 

 surface of ground is vastly greater when cov- 

 ered with trees and plants, than when covered 

 with standing water. Thus we come to one of 

 the first great uses of trees : they are the most 

 important agents of Nature for conveying the 

 moisture of the earth into the air. 



If a few cuttings will evaporate a half -pint of 

 water in twelve hours, how much more would be 

 exhaled by a tree I And what would a grove of 

 trees accomplish ! Over a forest, as over a lake, 

 there rests always, in calm weather, a stratum of 

 invisible moisture. This moisture is a good 

 conductor of electricity, and may be the direct 

 means of bringing down a shower. Electricity 

 is always of more or less importance in the 

 clouds. A cloud is made up of millions of little 

 vaporous particles suspended in the air and held 

 apart by a law of electricity which allows them 

 to come nearly together but will not allow them 

 to touch. The effect of the electric current is 

 lessened by cold and increased by heat. So 

 that, in summer, when earth and air are both 

 heated, and drought has prevailed for some 



