RESULTS OF BEAVERS' WORK 143 



geneous mass of material which under certain 

 conditions makes soil. Year after year the trees on 

 the surrounding hills and valleys have shed their 

 myriad leaves, and these have been blown into the 

 lake, or carried to it by the rains and melting snows. 

 Debris of all sorts has been brought down to the 

 flooded areas where in the still waters it all settles 

 to the bottom so that gradually a deep vegetable 

 muck has formed over the land that once was 

 covered with trees and flowers and richly coloured 

 mosses. Most of this refuse of the woods is under 

 normal conditions carried down by the various 

 streams into the rivers and so out to the sea and 

 apparently man gets no benefit from it. But the 

 beaver lake has arrested this valuable material and 

 prevented it going to waste. Instead of being lost 

 it has been stored up, not in one pond, but in 

 hundreds of thousands, large and small. With the 

 desertion of a beaver pond the water, as already 

 stated, being no longer held in check by the well- 

 built dams, gradually finds its way out. The sub- 

 sidence may be slow or rapid, but the effect is the 

 same. The whole area of flooded land begins to 

 dry, and what was formerly a rough irregular 

 tract has become smooth and level. For some 

 time the water-soaked land is too heavy to allow of 

 a good growth of vegetation, but it is opened and 

 ploughed by the winter frosts, while the sun and the 

 rains prepare it for its great mission. Grasses take 

 possession and soon the lake becomes a meadow 



