First, there are pontoons, large though light boats or punts, about 20 feet long, constructed of thin wood with canvas cemented all over to give additional strength and water-tightness. Each pontoon rides upon its own carriage upon which there are also stowed away quantities of timbers of various sorts, anchors for holding the pontoons in place, oars for rowing them, ropes of different kinds, and so on. Each pontoon, moreover, is divided about the middle into two pieces called respectively the bow piece and the stern piece. The two are normally coupled together by cunningly devised fastenings but they can be quickly separated, in which state they form two shorter boats. Other carriages carry more timber and material intended for the purpose of forming "trestle bridges" but which is also usable in connection with the pontoons. Of this material the chief sorts are "legs," long straight pieces which form the uprights; transomes, heavier beams which can be fitted across horizontally between two legs so that the three form a huge letter H or a very robust Rugby goal; "baulks" which are light timbers tapered off towards each end for the sake of lightness and of such size that they fit snugly into notches which are cut in the upper surface of the transomes; and planks called "chesses" for forming the floors of a bridge. Probably the most dramatic incident of the war was when the British, having been apparently beaten by the Turks in Mesopotamia, driven far back and their General and many troops captured, suddenly turned the tables upon their enemies, driving them from Kut and sending them fleeing helter-skelter to Bagdad and then beyond. Now the capture of Kut and then of Bagdad were both made possible by the rapid bridging of the Tigris, and without doubt this is the sort of material which was used. Let us see how it is done. An army arrives at a river across which it is decided to throw a pontoon bridge. The pontoons are unloaded off their wagons and launched into the water. One is rowed out and anchored a little way from the shore, while upon the bank parallel with the river is laid a "transome." On the centre of the pontoon is a centre beam with notches in it like those in the transomes and from the one to the other "baulks" are passed. Meanwhile a second pontoon has been rowed into place and more baulks are passed from the first pontoon to the second, while chesses are laid upon the baulks to form a platform or floor. Thus, pontoon by pontoon, the bridge grows until it has reached the further bank.