170 PRACTICAL ARBORICULTURE 



theories and evolved hypotheses, based upon the knowledge possessed during 

 their age of the world, which in the light of later discoveries have proven 

 false, and in many cases ridiculous, notably before the laws of gravitation 

 were known, and while the earth was yet flat, and rested upon impossible 

 animals. Yet they were quite as firm in their belief as some of our present 

 philosophers who, because they cannot understand, assert that forests have 

 no effect upon climate. Yet forest masses do concentrate moisture already in 

 the atmosphere and cause its precipitation upon the earth. 



An illustration of forest influence upon cloud distribution is found in the 

 Danish Island of St. Croix, one of the lesser Antilles, which group of islands 

 form a regular crescent from Porto Rico southward to Venezuela, and all 

 are wooded except St. Croix, from which the forests have been removed. This 

 island lies twenty miles south of St. Thomas, and without the regular cres- 

 cent of the group. The clouds follow the trend of the forest-covered islands 

 and rains are frequent, but St. Croix suffers severely from drought, as the 

 clouds are attracted from it yet in this tropic region the evaporation from 

 the Caribbean Sea is very great, fully as much at St. Croix as at St. Thomas, 

 but twenty miles away. 



It is also well known to farmers that summer showers so necessary for 

 agricultural prosperity follow the course of timber margined streams. 



In the Orient, so long as the forests remained upon the higher elevations, 

 the rain belt extended inland more than one hundred miles, but as the 

 mountains were cleared of their trees, the desert encroached upon the fertile 

 lands, gradually but surely, until all the land became arid. 



So the rainless plains of the United States have obtruded their aridity by 

 slow degrees, as extensive forests were destroyed by fires, by ice and by man, 

 until the Pacific has been reached throughout the greater part of California. 



The logical conclusion must be that forest covered elevations controlled 

 the distribution of moisture through the atmosphere and abundant rains pre- 

 vailed; but with the removal of these bodies of timber their influence was lost 

 and aridity was the consequence. 



