Forests and Snow. 
7 
during high water. The change is clearly connected with the diurnal 
effect of the sun. It is seen in the other diagrams, but almost disappears 
in cloudy weather. 
While the temperature has a marked influence in determining the 
general stage of the river, the direct action of the sun as shown by the 
diagrams is still more marked, as it causes these fluctuations. Anything 
which serves as a. protection from the sun, whether forests, ridges, boul¬ 
ders or clouds, lessens the melting and tends to decrease these tide's. 
This explains the paradoxical fact that a general rain in the mountains 
often lessens the amount of water in the river. 
This effect is illustrated by Fig. 5, which shows the record of a 
rainy week in 1898. On June 1 the diurnal fluctuation was slight, on 
