These two are the submarine mine and the torpedo. The latter, particularly, had been a dismal failure previously, but as the weapon of the submarine it has now established itself. It is, however, only in connection with the submarine that it has achieved any measure of success, and, as there are strong indications that very soon the submarine itself will be robbed of its terrors, it is quite likely that the reign of the torpedo will be brief. Although it has only just made itself felt seriously in warfare, the torpedo is a fairly old idea. In fact we can trace the general idea of it back to very ancient times. The modern weapon, however, dates from the year 1864, when an Austrian inventor approached an English engineer named Whitehead with a request to take up his idea. Mr Whitehead had at that time a works at Fiume, on the Adriatic, and it was really his genius that developed the crude idea into a practicable invention. Thus there came into existence the Whitehead Torpedo, now used in a great many navies, and also the Schwartzkopff, which may be regarded as the German variety of the same thing. Speaking generally, it may be described as a small automatic submarine boat. Externally, it naturally follows somewhat the lines of a fish. Deriving its name from that curious fish which is able to give electric shocks from its snout, it likewise carries on its nose that appliance whereby it gives a shock, not electric it is true, but equally deadly, to anything which it may touch. Since no man-made mechanism can approach the marvellous action of the fish's fins and tail, the propulsion is achieved by a propeller like that of a steamboat, but of course on a very small scale. A single propeller, however, would tend to turn the torpedo over and over in the water, and so it has two, one behind the other, driven in opposite ways, so that the turning tendency of one is neutralised by that of the other. The blades of the propellers are, however, set in opposite ways, so that although rotating in different directions they both push the torpedo along. Behind the propellers, again, there are rudders for steering. One steers to right or left, as does that of an ordinary ship, while two others are so placed that they can steer upwards and downwards. So there we have the general picture of the outside: a smooth, fish-like body with a "sting" in its nose, propellers at the rear to drive it along, and rudders to guide it. Inside are various chambers. One contains the explosive which blows up when the nose strikes something. This "head," as it is termed, is detachable, so that it can be left off until it is really required for war. The peace-head, which is of the same size, shape and weight as the war-head, is what the torpedo carries during its earlier career. With this it can be tried and tested in safety, the war-head being substituted when the real business of the torpedo begins.