FLOATING. 



373 



iv. Tanks. 



Dams can only be constructed across a stream in narrow 

 mountain-valleys, where they can rest on mountain-spurs on 

 both sides, without being necessarily of any considerable length. 



Fifj. 213. 



In wider and broader valleys with a slight fall, where there are 

 meadows and cultivated lands, and perhaps houses which a dam 



Fig. 2H. 



would obviously inundate, while its cost would be prohibitive, 

 owing to the large amount of compensation involved, it may, 

 nevertheless, be necessary to obtain larger supplies of water 

 for floating timber than the natural course of a stream affords. 



