Electric lights for vessels are now of recognized importance. At first they were objected to on the ground that if the wire carrying the current should be shot away in action, the whole ship would be plunged in darkness; and so it would be in an accident befalling the dynamo that generates the current. The criticism is sensible, but the answer is that different circuits must be arranged for different parts of the ship, and the wires carrying the current must be arranged in duplicate. It is also easy to repair a break in a copper wire if shot away. As to the dynamo and engines, they must be placed below the water line, under a protective deck, and this should be provided for in building the vessel. There should be several dynamos and engines. All the dynamos should, of course, be of the same electromotive force, and feed into the same mains, from which all lamps draw their supply, and which are fed by feeders from the dynamo at different points, so that accident to the mains in one part of the ship will affect that part only. But it is the arc light, used as what is called a search light, that is most valuable in warfare. Lieut. Fiske thinks its first use was by the French in the siege of Paris, to discover the operations of the besiegers. It can be carried by an army in the field, and used for examining unknown ground at night, searching for wounded on the battle field, and so on. On fighting vessels the search light is useful in disclosing the attack of torpedo boats or of hostile ships, in bringing out clearly the target for guns, and in puzzling an enemy by involving him successively in dazzling light and total darkness. Lieut. Fiske suggests that this use would be equally effective in embarrassing troops groping to the attack of a fort at night by sudden alternations of blinding light and paralyzing darkness. There should be four search lights on each side of a ship. As to the power and beauty of the search light, Lieut. Fiske refers to the magnificent one with which he lighted up Philadelphia last autumn, during the electric exhibition in that city. One night he went to the tower of the Pennsylvania railroad station and watched the light stationed at the Exhibition building on 32d street. The ray of light when turned at right angles to his direction looked like a silver arrow going through the sky; and when turned on him, he could read the fine print of a railroad time table at arm's length. Flashes from his search light were seen at a distance of thirty miles. In using incandescent lamps for night signaling, the simplest way is to arrange a keyboard with keys marked with certain numbers, indicating the number of lamps arranged in a prominent position, which will burn while that key is being pressed. For example, suppose the number 5348 means "Prepare to receive a torpedo attack." Press keys 5, 3, 4, 8, and the lights of lamps 5, 3, 4, 8, successively blaze out.