MAMMALS. 599 



largely hunted to obtain this substance, and the old hunters used to 

 declare that the animal knew their object, and that when pursued, he 

 would gnaw off the pouches, leaving them behind for the hunter, and thus 

 save his life. This castoreum was highly esteemed as a remedial agent, 

 and a list of the diseases it would cure is about equivalent to a complete 

 catalogue of all the ills that human flesh is heir to. The beaver is pictured 

 in all the older works as a marvel of knowledge, and the beaver communi- 

 ties as wonderful social organizations. Says Tonti, who accompanied La 

 Salle down the Mississippi over two hundred years ago, every beaver " is 

 obliged to work ; but if any one has his tail excoriated or otherwise hurt, 

 he lays it flat upon his back, to show that he is unable to work." Tonti 

 gives a pretty tolerable picture of a beaver community ; but the real 

 facts will hardly bear him out when he says, " they make a canal or sub- 

 terranean aqueduct from the river to one of the apartments, in which 

 they have a kind of pond, wherein they hold the tail ; otherwise they 

 could not live." 



Some of the other side, the reality of beaver life, now needs mention. 

 To-day but a few isolated communities can be found in the United States 

 east of the Mississippi, but in Canada and the northwest it has not yet 

 been exterminated. Elsewhere every specimen is caught as soon as found, 

 the white hunter paying no attention to the old Indian law of leaving some 

 in every pond to perpetuate the colony. Soon the few stragglers left in 

 northern Maine, in the Adirondacks, and in Virginia will be gone. 



The beaver, aside from its skin, is best known as an hydraulic engi- 

 neer and for the formation of its dams. In these respects it does not 

 always act as some accounts would indicate, for sometimes its instincts 

 are at fault ; but in general it displays an astonishing amount of skill in 

 its work. First comes the building of the dam, — a heavy, solid structure 

 reaching across some small stream. These are built by felling small trees 

 and underbrush with the sharp, strong, chisel-like teeth, and placing them 

 in the desired position, thus making a foundation. To this are now added 

 twigs, dead leaves, and mud, until a solid, water-tight structure is the 

 result. This dam is to make a pond in which the houses are placed. 

 These are rounded or oblong structures of brush, standing in the water 

 and covered with mud, and with the entrance or door below the water- 

 mark. The principal use of the pond is to afford an easy means of getting 

 their food to their houses. They eat the bark of various trees, and to 

 obtain it they cut down trees, sometimes of great size. This is done 

 entirely by gnawing round and round until at last the tree gives way ; 

 this process results in giving both the log and the stump a conical shape, 

 as shown in the cut. After the tree is down, the branches are lopped off, 



