i66 GEOLOGICAL SURVEY OF NEW JERSEY. 



from 20 to 30 per cent, of the area in the valleys and along the 

 stream channels is cleared of trees and in grass. The vegetable 

 matter in the water will be less for such conditions than when 

 the entire catchment is covered with forest. Such are about 

 the conditions which obtain on the Northeastern Highlands 

 streams already referred to. 



For hygienic reasons, therefore, as well as in order to preserve 

 a steady and uniform discharge, it becomes very important that 

 the forest cover shall be protected and preserved upon the catch- 

 ments which are to become gathering-grounds for the cities of 

 the State. 



