12 SOCIAL HABITATIONS. 
defended by a coating of long hairs, the broad, paddle-like 
tail, and the well-webbed feet, are characteristics which 
are at once intelligible. Water, indeed, seems to be an ab- 
solute necessity for the Beaver, and it is of the utmost im- 
portance to the animal that the stveam near which it lives 
should not run dry. In:order to avert such a misfortune, 
the Beaver is gifted with an instinct which teaches it how to 
keep the water always at or about the same mark, or, at all 
events, to prevent it from sinking below the requisite level. 
If any modern engineer were asked how to attain such 
an object, he would probably point to the nearest water- 
mill, and say that the problem had there been satisfactorily 
solved, a dam having been built across the stream so as 
to raise the water to the requisite height, and to allow the 
superfluous water to flow away. Now water is as needful 
for the Beaver as for the miller, and it is a very curious 
fact, that long before millers ever invented dams, or before 
men ever learned to grind corn, the Beaver knew how to 
make a dam and insure itself a constant supply of water. 
That the Beaver does make a dam is a fact that has 
long been familiar, but how it sets to work is not so well 
known. Engravings representing the Beavers and their 
habitations are common enough, but they are generally 
untrustworthy, not having been drawn from the natural 
object, but from the imagination of the artist. In most 
cases the dam is represented as if it had been made after 
the fashion of our time and country, a number of stakes 
having been driven into the bed of the river, and smaller 
branches entwined among them. ‘The projecting ends of 
the stakes are neatly squared off, and altogether the work 
looks exactly as if it had been executed by human hands. 
One artist seems to have copied from another, so that the 
error of one man has been widely perpetuated by a series 
of successors. 
