We will assume, for purposes of illustration, that the Sandy Hook entrance to New York Harbor is to be defended. If we strike a fifteen-mile radius from Sandy Hook point, running from the Long Island to the New Jersey shore, and have four submarines take station on that radius line about five miles apart, no ship could pass that radius line without coming within the range of vision of the commander of the submarine, either from his periscope in daylight or at night within the range of hearing of his "submarine ears." The Fessenden oscillators, or microphones, now installed in all submarines, would readily detect the approach of a surface ship or ships. These instruments have been improved to such an extent that it is now possible to carry on wireless conversation under water between one submarine and another for a considerable distance. Communication by the Morse code, or other special codes, may be carried on between submarines up to a distance of several miles. It would be possible for groups of submarines on station, or picket duty, so to speak, to be in constant communication with shore stations, either by submerged telephone stations or by wireless. In that way the submarines can be kept in constant touch with the country's scouting fleet of high-speed surface vessels or aeroplanes and immediately be notified of the approach of an enemy's fleet or ship. There is no way in which they can themselves be detected, so far as I am aware, as there is no need to run the machinery of the submarine while lying at rest on picket duty, and it would be impossible for a surface ship or flying machine to detect them, providing a constant watch was kept on the horizon or the heavens through the aeroscopes. As the effective range of the modern Whitehead torpedo is about three miles, no ship could pass between the submarines without passing within torpedo range. However, a commander of a submarine would hardly take a chance of making a hit at such great distance, and on sighting the enemy he would leave his station and attempt to intercept her, so as to get a shot at shorter range. If the enemy succeeded in running the gauntlet of the outer circle it would have to pass the submarines distributed on, say, a ten-mile radius. Three submarines would be able to protect this radius line. A five-mile radius might also be established with two submarines, and one located at the entrance. To enter Sandy Hook, therefore, a ship would have to run the gauntlet of five or six submarines without it being necessary for them to leave their stations. Submarines with high speed will become valuable as commerce destroyers and for carrying on an offensive warfare. Page 32 shows a high speed, sea-keeping, fleet submarine of the "Lake" type. Its principal characteristics are the same as those of the coast-defence type, except that the buoyant superstructure is increased in height sufficiently to form living quarters for the crew when cruising in surface condition.