But when the tube has been bored, turned, and rifled, the gun is by no means finished. The tube by itself would be far too delicate for the large charges of powder employed; and, consequently, it has to be fitted at the breech end with two or three outer cases or jackets, the outside one of which bears the trunnions on which the gun rests. At last the gun is completed; and the next thing is to subject it to a severe test by firing from it a charge of powder proportioned to its size. For this purpose, it has to be taken to Plumstead Marshes, a portion of which forms the testing-ground and powder-magazines connected with the Arsenal. Lines of railway run down to the marshes, and the gun is mounted on a truck and dragged off by a locomotive to the place appointed for its trial. It may be mentioned that lines of railway run in all directions through the Arsenal, one of narrow gauge being introduced into most of the workshops, so that the visitor has to keep a lookout lest a tiny locomotive with a train of what may almost be called toy trucks should bear down upon him as he is walking along.--But to return to the gun. When it has been finally tested, cleaned, polished, and stamped, it is coated with a particular varnish, and is fit for service. The next most interesting place to the Gun Factory is the Laboratory, where shells and bullets are manufactured. Shells are cast rough, and then finished off in a lathe. A band of copper now usually takes the place of the copper studs which were formerly inserted to enable the shell to fit into the rifled grooves. This band is expanded by the force of the explosion when the gun is fired, and fills up the grooves, so as to give the necessary spin to the shells. Shells are charged with their interior bullets at the Laboratory; but the powder is added down at the marshes. A shell when completed has become a very expensive article, especially if it is a large one. Some of those projectiles are so heavy that the guns from which they have to be fired are provided with small cranes for lifting them up to the breech. The shells are, like the guns, beautifully finished off and varnished, and then sent off to the stores. Perhaps the most interesting place in the Laboratory department is the Pattern Room, which is a sort of museum where shot and shells of all sorts are to be seen, from the old-fashioned chain-shot, made of round balls fastened together, to the most perfect specimens of modern shells. Here, also, are to be seen those strange weapons of modern warfare called torpedoes, amongst them the famous 'fish torpedo,' which with its complicated mechanism may be almost described as an under-water ship. It is so constructed that it finds its way unseen and unheard, with its terrible charge of dynamite, to the side of a hostile vessel. THE ENFIELD SMALL-ARMS FACTORY.