EFFECT OF FORESTS ON A COUNTRY. 13 
its flow in consequence of cutting away the trees along 
its banks, exposing its waters to the hot sun. 
The island of Santa Cruz, in the West Indies, which 
twenty-five or thirty years ago was a garden, is now 
almost a desert in consequence of cutting away the for- 
ests. The theory is that the dry currents of air are re- 
tarded by forests, and elevated until a point of conden- 
sation is reached. Radiation is also prevented, the air 
cooled, and the clouds, passing over trees, are rendered 
more easily condensed. Electricity is also a great agent, 
‘the trees being negatively charged, and drawing with | 
great power the positively charged clouds. This theory ' 
is no longer a matter of doubt or experiment, but a fact’ 
demonstrated by experience and a knowledge of the 
Jaws that govern the atmosphere. Pe 
But not only in Europe, but in America, is the loss of 
timber already lamentably felt. Many of our rivers 
have lost half their usefulness for manufacturing pur- 
poses. The Connecticut is hardly navigable, and the! 
Kennebec and Merrimac have shrunk one fourth. The: 
Potomac has lost nearly one fourth of its volume, and} 
the Hudson declined a sixth. Ifthe Adirondack wilder: 
ness and other forests adjacent were destroyed it would 
probably, in time, render the Hudson wholly unnavi- 
_gable. 
As has been explained, forests are vast reservoirs of 
humidity—lessening the dryness of the surrounding at- 
mosphere, and aiding the perennial flow of springs and 
streams. Says Bryant, “instances are on record of the 
drying up of springs and rivulets when the woods which 
shaded them were felled, and of their reappearance when 
the trees were suffered again to grow.” 
The increase of rainfall in Lower Egypt since the for- 
mation of extensive plantations of trees is proof of their. 
effect upon the rainfall of a country. In 1869 there 
were fourteen rainy days at the Isthmus of Suez, where 
rain had rarely if ever before been known, and the 
