streams at the time of low water, the result being 

 a more even stream-flow at all times. 



The regulation of stream-flow is important. 

 There are only a few rainy days each year, and 

 all the water that flows down the rivers falls 

 on these few rainy days. The instant the water 

 reaches the earth, it is hurried away toward the 

 sea, and unless some agency delays the run-off, 

 the rivers would naturally contain water only on 

 the rainy days and a little while after. The fact 

 that some rivers contain water at all times is but 

 evidence that something has held in check a por- 

 tion of the water which fell during these rainy 

 days. 



Among the agencies which best perform this 

 service of keeping the streams ever-flowing, are 

 the forests and the works of the beaver. Rainfall 

 accumulates in the brooks. The brooks conduct 

 the water to the rivers. If across a river there be 

 a beaver-dam, the pond formed by it will be a 

 reservoir which will catch and retain some of the 

 water coming into it during rainy days, and will 

 thus delay the passage of all water which flows 

 through it. Beaver-reservoirs are leaky ones, and 



63 



