2Y2 NATURE'S TEACHINGS. 



These branches, and not any supposed stakes, are really the 

 upright supports of the dam. The trees being thus laid, the 

 Beaver cuts down branches from four to six feet in length, and 

 lays them horizontally among the boughs of the fallen trees. 

 Having thus made the foundations, so to speak, of its dam, the 

 Beaver then proceeds to fill in the spaces with roots, grass- 

 tufts, leaves, mud, and, indeed, almost anything on which it 

 can lay its paws. 



After this, the Beaver has to take but little trouble, for the 

 stream itself becomes a silent, slow, but constant labourer, 

 lodging floating debris against the dam, and making a sloping 

 bank which much adds to its strength. By degrees, seeds that 

 lodge on the dam spring into life, and their roots act like 

 chains, binding the materials more closely together. "Willow 

 twigs too, if they lodge on the dam and be left undisturbed, are 

 sure to " strike," as the gardeners say, and further to bind the 

 structure together. 



It is evident, from this short description, that the lower part 

 of the dam is more solid than the upper. In fact, the floods 

 are tolerably sure to wash away some eight or ten inches of the 

 upper part every year, and the Beavers have to make it afresh. 

 The height of these dams is not nearly so great as is generally 

 supposed. Mr. Green, a practical trapper, states that the 

 highest which he ever saw was only four feet six inches in 

 height, and that the average is under three feet. 



The house of the Beaver is made on the same principle as 

 the dams. Every one knows that when sticks have been in the 

 water for any length of time, they become saturated and sink. 

 These sticks are chosen by the Beaver as the material for its 

 house, and are laid horizontally in the water, the heaviest 

 being reserved for the roof, so as to make it strong enough to 

 ward off the attacks of predacious animals. As with the dam, 

 mud, leaves, &c, are used to consolidate the edifice, but no 

 mud can be seen from the outside, the animal always finishing 

 off with a number of heavy logs laid on the roof. 



Subterranean Dwellings. 



I do not intend in this place to take up the whole subject of 

 Subterranean Dwellings, but only to point out cases where the 

 use of the Subterranean Dwelling depends on the climate of 



