its chisel-like teeth cutting a bold groove completely round the trunk. It then widens the groove, and always makes it wide in exact proportion to its depth, so that when the tree is nearly cut through, it looks something like the contracted portion of an hour-glass. When this stage has been reached, the Beaver looks anxiously at the tree, and views it on every side, as if desirous of measuring the direction in which it is to fall. Having settled this question, it goes to the opposite side of the tree, and with two or three powerful bites cuts away the wood, so that the tree becomes overbalanced and falls to the ground.

This point having been reached, the animal proceeds to cut up the fallen trunk into lengths, usually a yard or so in length, employing a similar method of severing the wood. In consequence of this mode of gnawing the timber, both ends of the logs are rounded and rather pointed, as may be seen by reference to the illustration. In the Zoological Gardens may be seen many excellent examples of timber which has been cut by the Beaver: the logs and cut stumps which are given in the illustration were sketched from those objects.

The next part of the task is to make these logs into a dam. Now, whereas some persons have endeavored to make the Beaver a more ingenious animal than it really is, and have accredited it with powers which only belong to mankind, others have gone to the other extreme, and have denied the existence of a regularly built dam, saying that it is entirely accidental, and caused by the logs that are washed down by the stream, after the Beavers have nibbled off all the bark.

That this position is untenable is evident from the acknowledged fact that the dam is by no means placed at random in the stream, just where a few logs may have happened to lodge, but is set exactly where it is wanted, and is made so as to suit the force of the current. In those places where the stream runs slowly, the dam is carried straight across the river, but in those where the water has much power, the barrier is made in a convex shape, so as to resist the force of the rushing water. The power of the stream can therefore always be inferred from the shape of the dam which the Beavers have built across it.

Some of these dams are of very great size, measuring two or three hundred yards in length, and ten or twelve feet in thickness, and their form exactly corresponds with the force of the stream, being straight in some parts, and more or less convex in others.

The dam is formed, not by forcing the ends of the logs into the bed of the river, but by laying them horizontally, and covering them with stones and earth until they can resist the force of the water. Vast numbers of logs are thus laid, and as fast as the water rises, fresh materials are added, being obtained mostly from the trunks and branches of trees which have been stripped of their bark by the Beavers.

The reader will remember that many persons have thought that the dam of the Beaver is only an accidental agglomeration of loose logs and branches, without any engineering skill on the part of the animals. There is some truth in this statement, though the assertion is too sweeping; for, after the Beavers have completed their dam, it obstructs the course of the stream so completely that it intercepts all large floating objects, and every log or branch that may happen to be thrown into the river is arrested by the dam, and aids in increasing its dimensions.

Mud and earth are also continually added by the Beavers, so that in process of time the dam becomes as firm as the land through which the river passes, and is covered with fertile alluvium. Seeds soon make their way to the congenial soil, and in a dam of long standing forest trees have been known to grow, their roots adding to the general stability by binding together the materials. It is well known that the fertile islands formed on coral reefs are stocked in a similar manner. Originally the dam is seldom more than a yard in width where it overtops the water, but these unintentional additions cause a continual increase.

The bark with which the logs were originally covered is not all eaten by the animals, but stripped away, and the greater part hidden under water, to serve for food in the winter time. A farther winter provision is also made by taking the smaller branches, diving with them to the foundations of the dam, and carefully fastening them among the logs. When the Beavers are hungry, they dive to their hidden stores, pull out a few branches, carry them on land, nibble away the bark, and drop the stripped logs on the water, where they are soon absorbed by the dam.

We have now seen how the Beavers keep the water to the required level, and we must next see how they make use of it. The Beaver is essentially an aquatic mammal, never walking when it can swim, and seldom appearing quite at its ease upon dry land. It therefore makes its houses close to the water, and communicating with it by means of subterranean passages, one entrance of

which passes into the house or "lodge," as it is technically named, and the other into the water, so far below the surface that it can not be closed by ice. It is, therefore, always possible for the Beaver to gain access to the provision stores and to return to its house without being seen from the land.

The lodges are nearly circular in form, and much resemble the well-known snow-houses of the Esquimaux, being domed, and about half as high as they are wide, the average height being three feet, and the diameter six or seven feet. These are the interior dimensions, the exterior measurement being much greater, on account of the great thickness of the walls, which are continually strengthened with mud and branches, so that, during the severe frosts, they are nearly as hard as solid stone. Each lodge will accommodate several inhabitants, whose beds are arranged round the walls.

All these precautions are, however, useless against the practiced skill of the trappers. Even in winter time the Beavers are not safe. The hunters strike the ice smartly, and judge by the sound whether they are near an aperture. As soon as they are satisfied, they cut away the ice and stop up the opening, so that if the Beavers should be alarmed, they can not escape into the water. They then proceed to the shore, and by repeated soundings trace the course of the Beavers' subterranean passage, which is sometimes eight or ten yards in length, and by watching the various apertures are sure to catch the Beavers. This is not a favorite task with the hunters, and is never undertaken as long as they can find any other employment, for the work is very severe, the hardships are great, and the price which they obtain for the skins. is now very

small.

While they are thus engaged, they must be very careful not to spill any blood, as, if they do so, the rest of the Beavers take alarm, retreat to the water, and can not be captured. They also have a curious superstitious notion, which leads them to remove a knee-cap from each Beaver and to throw it into the fire. They would expect ill luck were they to omit this ceremony, which is wonderfully like the custom of our fishermen of spitting into the mouth of the first fish they catch, and the first money which they take in the day, "for luck."

Generally, the Beavers desert their huts in the summer time, although one or two of the houses may be occupied by a mother and her young offspring. All the old Beavers who have no do

mestic ties to chain them at home take to the water, and swim up and down the stream at liberty until the month of August, when they return to their homes. There are also certain individuals, called by the trappers "les paresseux," or idlers, which do not live in houses, and make no dam, but abide in subterranean tunnels like those of our common water rat, to which they are closely allied. These "paresseux" are always males, and it sometimes happens that several will inhabit the same tunnel. The trapper is always pleased when he finds the habitation of an idler, as its capture is a comparatively easy task.

CHAPTER XXII.

SOCIAL BIRDS.

The SOCIABLE WEAVER BIRD and its Country.-Description of the Bird.-Nest of the Sociable Weaver.-How begun and how carried on.-Materials of the Nest. -The Tree on which the Nest is built, and its Uses.-Dimensions of the Nest and disastrous Consequences.-A Hottentot and a Lion.-Supposed Object of the Social Nest.-Average Number of Inhabitants.—Analogy with Dyak Houses. -Enemies of the Sociable Weaver, the Monkey, the Snake, and the Parrakeet.

WE now come to the SOCIAL BIRDS, one of which is as preeminent among the feathered tribes as is the beaver among mammalia. This is the SOCIABLE WEAVER BIRD, sometimes called the SOCIABLE GROSBEAK (Philetrus socius).

This species is allied to the Weaver Birds, some of which have already been described, and makes a nest which is no whit inferior to those which have already been mentioned. The Sociable Weaver Bird is a native of Southern Africa, and in some places is very plentiful, its presence depending much upon the trees which clothe the country. It is not a large bird, measuring about five inches in length, and is very inconspicuous, its color being pale buff, mottled on the back with deep brown.

The chief interest about the species is concentrated in its nest, which is a wonderful specimen of bird architecture, and attracts the attention of the most unobservant traveler. Few persons expect to see in a tree a nest which is large enough to shelter five or six men, and yet that is often the case with the nest of the Sociable Weaver Bird. Of course so enormous a structure is not the work of a single pair, but, like the dam of the beaver, is made by the united efforts of the community. How it is made will now be described.

Large as is the domicile, and capable at last of containing a vast number of parents and young, it is originally the work of a single pair, and attains its enormous dimensions by the labors of those birds which choose to associate in common. The first task of this Weaver Bird is to procure a large quantity of the herb which really seems as if made expressly for the purpose. This is a grass with a very large, very tough, and very wiry blade, which is known to the colonists as Booschmannie grass, probably because it grows plentifully in that part of Southern Africa where the Bushmen, or Bosjesmans live.

They carry this grass to some suitable tree, which is usually a species of acacia, called by the Dutch colonists Kameel-dorn (Acacia giraffa), because the giraffe, which the Dutch persist in calling a kameel or camel, is fond of grazing on the leaves. This is a most appropriate tree for the purpose, as the wood is extremely