10 
Bulletin 55. 
In this case, over 90 per cent of the watershed is below timber line and 
above 8,000 feet. 
That the forests in the mountains increase the amount of precipita¬ 
tion does not seem probable, whatever their effect when on the plains or 
lands of low elevation may be. The precipitation in the mountains is 
mostly due to the cooling from expansion, caused by the air being forced 
upward by the mountains. The effect of the forests would be so small 
compared with the mountains that it does not seem possible that they 
would increase the amount of rainfall. It, however, is not impossible 
that in the maintenance of moist conditions, influence on the currents 
of air, and the protection of slopes from the burning rays of the sun, 
there ma}^ be an effect even on the amount and distribution of the 
rainfall. Nevertheless, they influence the river floods, and protect the 
snows from melting and the action of the winds. As a protection from 
floods, they form a feature which the agricultural interests of the State 
should jealously protect. 
