The British naval authorities took measures to guard British shipping in the English Channel by stretching nets over as much of the water, particularly in the narrows, as possible. The nets are made of links of steel. These links are about six or eight inches in diameter and made of one-half inch steel. The nets are similar to those formerly used to guard battleships and large cruisers, but which have now been discarded because a torpedo will puncture the net and the second torpedo, which is fired only a second or two after the first, will go through the hole made by the first and reach the hull of the vessel. These chain nets are moored very securely and have buoys at the upper edges to hold them in position. Often they are set just as a fisherman sets his nets. When the submarine, like a fish, gets in the pound it cannot get out, and those in the vessel must either die there or take chances on reaching the surface and swimming to shore. It takes very little to disable a submarine. The hull is of comparatively thin steel which is easily punctured and the propeller when caught is absolutely useless. Even an ordinary fisherman’s net will disable a submarine, and should one get foul of such a net the chances of getting clear are very slim. According to the German naval press, the latest submarines are fitted with double acting Diesel oil engines of 1,000 horse power or more. These engines are as simple and run as smoothly as marine steam engines and are as easily controlled. So strongly built are these craft that they can plunge to a depth of 150 feet, at which the water pressure is enormous. HOW CRAFT SUBMERGE A security weight, as it is called, of about five tons is carried. This can be released from the inside of the vessel at a moment’s notice, and the effect is like that of dropping a mass of ballast from an airship. When in diving trim, that is to say, when the boat is awash, an up-to-date submarine can disappear under water in fifteen seconds and re-emerge in twenty seconds. It can remain under water for a whole day and night, or even longer. A submarine when submerged is handled mechanically. Those in charge cannot see where the vessel is going. The officer in charge steers according to the ranges he has taken when on the surface, and it is absolutely impossible to see obstructions that may be ahead. It is impossible to see another submarine unless the two are floating near the surface and in bright daylight. For this reason it is impossible for one submarine to fight another when submerged. CHAPTER XXX THE TERRIBLE WORK OF ARTILLERY IN WAR SEVENTY PER CENT OF CASUALTIES DUE TO ARTILLERY FIRE -- INCREASED RANGE -- MODERN GUNS -- RAPID FIRING -- HOW A BIG GUN IS AIMED -- AWFUL DESTRUCTIVENESS OF MODERN GUNS.