PRACTICAL ARBORICULTURE 



81 



ductions of farms have so decreased that business for boats no longer exists as in 

 former times. 



It is not fully recognized that the forests very largely control the transpor- 

 tation of produce, both on land and upon inland waters, but this is nevertheless 

 true. 



As \ve have shown, erosion from hills and farms, filling the streams with 

 silt, has been the principal cause of irregularity of depth in the waters of rivers, 

 and a hindrance to free navigation. One of the great items of expense in the 



A KOREAN PORTER 



United States is the river and harbor expenditures, to overcome this filling up of 

 the channels, which each year is giving greater trouble. 



Then electricity is controlled by forest trees which are the principal means of 

 communication between the earth and the clouds, and as the volume of water 

 which the atmosphere can retain is altogether regulated by the presence of a greater 

 or less quantity of the electric fluid, the presence or absence of ample forest bodies 



