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 
anunals. 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 les 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 destroved 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. 
