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. 
Débris 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 
