300 PROCEEDINGS OF THE 



of the soil, and thus filling the reservoir with silt and 

 debris, shortens their periods of usefulness, and de- 

 stroys their efficiency. That deforestation does 

 result in an increase in the amount of sediment con- 

 veyed by the running water has been amply demon- 

 strated by investigations carried on both in this country 

 and in others. All measurements of silt, so far as is 

 known, indicate that the run-off from unprotected 

 areas is much more heavily laden with gravel, sand, 

 earth, and organic matter than is the discharge from 

 areas well protected by forests. 



Where storage is not practiced, forestation still 

 remains an important factor in power development, 

 since a requisite of the utilization of the water supply 

 for this purpose depends to some extent upon the 

 freedom of the water from impurities. The presence 

 of a greater or less quantity of silt or sand in the water 

 supply has an important bearing upon the longevity of 

 the machinery, especially the cups and bearings of the 

 impulse wheels. The more rapid deterioration in the 

 machinery may represent a very greatly increased cost 

 in the development of power and a consequent limita- 

 tion to its sphere of usefulness. 



Practically all that has been said concerning the 

 development of electrical energy is applicable also to 

 the development of power directly and through the 

 compression of air through the agency of water falling 

 through a shaft, a process which it is predicted will 

 become much better known and utilized in the future 

 than it has been in the past. 



Having established the fact that there is a close rela- 

 tion existing between forests and the development of 

 power through the medium of our streams it is an easy 

 task to demonstrate the necessity for forest reserves 

 and for their proper control and management. 



It is clear that forest lands still remaining in the 



