In the winter, when the snow covers the whole country with one uniform sheet of white, except where the wind blows the snow aside, and exposes the underlying stones, the Ptarmigan assumes a different plumage, being almost entirely white, except a black streak over the eye, and the outer feathers of the tail, which are also black. Thus the bird becomes almost indistinguishable from a snow-covered stone, especially as it has a habit of squatting motionless and silent when it takes alarm. The reader may, perhaps, remember that the common Stoat also has a summer and winter dress. The ordinary colour is rich reddish brown above, and white beneath, with a black tip to the tail. In the severe winters of Northern Europe the Stoat exchanges his ruddy coat for one of pure white, and is then known by the name of Ermine. It is remarkable that in the winter dress both of the Ptarmigan and Stoat the tail is black, while the rest of the coat is white. THE TRENCH. We now come to a third mode of concealment in war, namely, that which is obtained by means of Trenches or Pits. Even in hunting the pit or partial trench is largely used. In Southern Africa the hunter often employs such a trench, called technically a “Skärm.” It is very simple in idea, and easily made, being based on the principle that lions, elephants, &c., look for their assailants on the level of the earth, and seldom, if ever, look above or below it. Accordingly the hunter, having marked some pool or lake whereunto the wild animals resort at night to quench their thirst, chooses a convenient spot, and there digs a trench some seven feet in length and four deep, and covers it in with stout tree-branches and logs of various size. The whole is roofed in with sods, and the only entrance is at one end. Here the hunter sits and waits, and, as his ear is on a level with the surface of the ground, he can hear at a considerable distance sounds which would have escaped him had he been erect. Waiting for a favourable opportunity, as the various beasts come to drink, the hunter chooses one, takes careful aim, and fires one of his heaviest guns. It is but seldom that the rest of the animals charge in the direction of the Skärm, but even if they do, the hunter is quite safe under the shelter of his strong roof, which is able to resist even the heavy tread of an elephant. [Illustration: Galleria-Moth (Larva).] [Illustration: Military Trench.] In modern warfare, and especially during sieges, the trench is largely used, and is constructed on the most scientific principles, so as to shelter the assailants, while enabling them to proceed nearer and nearer to the fortress. A portion of one of these trenches is shown in the right hand of the illustration. * * * * * ON the opposite side of the same illustration is shown the same principle as carried out in Nature.