If pontoons are scarce and the loads to be carried by the bridge are light they are divided in two, and instead of a row of pontoons joined by "baulks" there is a row of "pieces" joined by baulks. Pieces arranged thus form a light bridge, pontoons a medium bridge, while pontoons placed closer together form a heavy bridge. Which shall be built depends upon the number of pontoons available in relation to the width of the river and the nature of the traffic which will have to pass over. An alternative arrangement is to make the pontoons up first into groups or rafts and then bridge from raft to raft instead of bridging between pontoons. There is still another way of making the bridge, and that is to put it together alongside the bank, afterwards swinging it across the river like the opening or shutting of a door. Anyone can see that there must be many advantages in this latter method when it is practicable, since more men can work at once and with greater safety, for all will be near the bank. It is evident that such a structure depends for its security entirely upon the anchors. Those which are carried for the purpose are like those of a ship but there may not be enough or they may not suit every kind of river-bed. They are often improvised therefore. Two wagon wheels lashed together, with heavy stones clipped between them, are said to be a very effective anchor. Under certain conditions a net filled with stones is surprisingly effective. Two pickaxes tied together form a good imitation of the conventional anchor, as also does a harrow sunk and held down by stones thrown upon it. Trestle bridges are made in quite a different way. The trestles are formed of two legs or uprights with a transome between, a shape which resembles, as has been already remarked, a very robust Rugby goal. The transome is connected to the legs by a special form of band which permits it to be fixed at any height without having to drill any special holes for the connections. The legs are so shaped at their ends that they can be shod with steel shoes provided for the purpose, enabling them to get a good foothold even on shifty soil. The trestles are put together ashore, and each is taken out in a boat or on a pontoon to the place where it is to stand. Then it is launched feet foremost into the water, the boat being on the side away from the shore, so that a rope from the trestle to the shore will enable men on land to pull the trestle into an upright position. [Illustration: AN INCIDENT AT LOOS. This picture gives us some little idea of the devastation caused by modern weapons. It also shows the inventiveness of the soldier who makes his rifle into a battering-ram. Incidentally we see a kind-hearted soldier rescuing a little girl from danger. This incident really happened.]