Torpedo-boats, as their name implies, depend entirely upon the torpedo as the weapon of attack, and they carry no guns except a very few light-calibre rapid-fires to keep off small boats. Their success depends on their ability to approach a vessel very rapidly, launch their torpedo, and retreat before they are detected and sunk. Speed is their great requisite, and a torpedo-boat like the _Porter_ can speed thirty-two miles an hour. Naval experts consider their bark worse than their bite, because, with the modern system of lookouts and search-lights, and the accuracy and rapidity of the secondary batteries, it is impossible for a torpedo-boat to get within range without exposing itself to instant destruction, and after a torpedo-fleet has once met with a serious repulse, it is believed that it would be almost impossible to get the crews to go into action again. The torpedo-boat destroyer, contrary to general belief, does not carry any heavy guns, but depends on its great speed and its ability to cripple a torpedo-boat with its 6-pounders while keeping out of range of the enemy’s tubes. All torpedo-boat destroyers carry torpedo tubes themselves, so that they can be used against the enemy’s battle-ships or cruisers if the occasion offers. The fastest boat in the United States navy is the destroyer _Bailey_, which can steam thirty-four miles an hour. In a naval battle the success or failure of a fleet may depend on keeping open communication between the different vessels of the squadron engaged. Owing to the fact that the surface of the sea would often be obscured by the smoke of battle, the difficulty of this is apparent, and naval experts have been kept busy devising some method by which the flag-ship can communicate with the other vessels of the squadron at all times and under all conditions. So far nothing has been put in general service which meets this demand, but lately there have been experiments with the telephone, which, it is said, can be used without wires, by which signals can be projected by a vibrator on one vessel against a receiver on another. The Navy Department is keeping the details of this new system carefully to itself, as it desires to have the invention for the exclusive use of our own ships of battle. The present method of communication is by the use of flags representing numerals which are displayed in the rigging; by the use of the Ardois system of lights for night work; by the Myer code of wigwag signals, and by the use of the heliograph. As it is of the utmost importance that the enemy should not read the message, the signal books on board a vessel are protected with the greatest care, and are destroyed along with the cipher code whenever it is seen that capture is inevitable. The semaphore system in use in the British navy was tried for a time aboard some of our vessels, but it never became popular, and has been abandoned.