The Zeppelins are well armed with machine guns, carrying one in each of the two cars, and one on top of the structure. Access is had to the latter by means of a shaft and ladder which passes up through the gas-chambers. ACCURACY IN DROPPING BOMBS The Zeppelins have elaborate bomb-dropping apparatus with which it should be theoretically possible to drop a bomb with great accuracy, but on the occasion when it was tried at Antwerp, the Germans met with no great success. The principle of the bomb-dropping device is as follows: A sort of camera, pointed vertically downwards, is used, and an observer notes the speed with which an object on the ground passes across the field, and the direction in which it appears to move. He then reads the height of the airship from the barometer, which gives the time taken by the bomb to fall, say fifteen seconds for 3,500 feet. He has now to calculate, from the data given by the camera-observation, the allowance to be made for speed and leeway for fifteen seconds of fall, and to point his sighting-tube accordingly. The air-ship is steered to windward of the target, and at the moment when the target (say, the second funnel of a dreadnaught) appears on the cross wires, the nine hundred-pound bomb is dropped, and the ship goes to the bottom. [Illustration: SCENE OF AIR RAID ON ENGLAND. Leigh, shown on the map, is only twenty-five miles from the British capital, and South End just five miles further on. The fleet of Zeppelins, or aeroplanes, or both, it will be seen, got uncomfortably close to the British metropolis.] CHAPTER XXIX THE DEADLY SUBMARINE AND ITS STEALTHY DESTRUCTION NEW COMPLICATIONS IN NAVAL ATTACK -- ATTACK ON LINER DESCRIBED -- OPERATION OF TORPEDOES -- NETS TO TRAP SUBMARINES -- HOW CRAFT SUBMERGE. What is the value of the submarine in war? Is it so great that all our theories of naval attack and defense will have to be revised? Are the great battles of the future to be fought under water? Is a little vessel of a few hundred tons to make the dreadnaught useless? German naval tactics in the present war have made these questions interesting alike to the expert, who has his answers to them, and to the layman, who is profoundly ignorant on the whole subject. Simon Lake, an inventor who has done much to bring the submarine to its present degree of efficiency, says that “it is the first weapon which has a potential power to destroy an invading force, and also to prevent an invading force from leaving its own harbors or roadsteads, but which is itself useless for invading purposes.” This is at once an exaltation and a limitation of its effectiveness. Yet Captain Lake believes that it will be “the most potent influence that has been conceived to bring about a permanent peace between maritime nations.”