Page:Collier's New Encyclopedia v. 09.djvu/169

LEFT SUBMABINES 135 SUBMABINES electrical firing was used, the mines be- ing connected to a station on shore by cable. In recent years, however, gun- cotton has been replaced by trinitroto- 6UN IN RECESS vane." This consisted of two "otters** towed by wire ropes from the side of a vessel. The otters were fitted with saw- like jaws, and a mine would glide along SUN IN USE SUBMARINE'S GUNS luene (T. N. T.) and the North Sea bar- rage referred to above is said to have contained more than 21 million pounds of this explosive. Much of the wartime development was concerned with render- ing explosion more certain snd more easily brought about. The American navy was especially successful along these lines. The details of manufacture are necessarily kept a close secret, but it is known that both British and German mines were of the so-called "horn type," being fitted with leaden horns, which pro- jected from the mine. When these horns were struck and broken by a passing ship, or any other body, the explosion of the mine was brought about. The Amer- ican mine was invented shortly after the United States entered the war. It was fitted with a long antenna which stretched above the mine. When this antenna was struck by a ship the ex- plosion of the mine followed. It is ob- vious that the radius of action of a mine fitted with such a device is very much greater than that of the horn type. Moreover, the explosion depended upon electrical action, and it was only neces- sary for a piece of metal to make con- tact with the antenna for an explosion to follow. Mines are destroyed by "sweepers." A heavy wire is attached to the stern of two vessels, and the wire is kept at a sufficient depth by means of a pipe. The vessels sail through a sus- pected mine field, and when a mine is caught in the sweep wire, it is dragged along until the wire which holds it to its anchor breaks. The mine then rises to the surface, and can be destroyed by gunfire. Another protective device against mines invented by the British navy during the war was the "para- the length of the wires until it reached the otter, when the wire would be cut and the mine destroyed. Submarine Navigatio'ti. — Under-water vessels had never been used in war- fare to any appreciable extent until the European War of 1914-1918. Many attempts at submarine navigation have been made, however, during the last 300 years. One of the earliest inventoi's to meet with anything approaching success was Cornelius Drebbell, a Dutchman, who built a boat manned by twelve row- ers, and navigated it on the River Thames. This was at the beginning of the 17th century. In 1744, another in- ventor named Day, built a boat which he claimed could remain under water for twelve hours. He lost his life, however, in an attempt to prove the truth of his assertion, being drowned iu his own boat in Plymouth Sound. In the follow- ing year, Bushnell, an American, in- vented a submarine vessel which met with considerable success. Some of the principles employed by him are still used in modern vessels. His boat was fitted with "oars on the principle of a screw," and submerged by admitting water through a valve, the water being pumped out when it was wished to rise' to the surface. The next inventor was Robert Fulton, who, in 1800, remained under water for four hours, at a depth of 25 feet, in an egg-shaped vessel of his ovm devising. He indicated future possibili- ties in this line by attaching a charge of explosives to an old hulk off the coast of France and blowing her up. In 1830 a German named Bauer made some un- successful experiments with a boat which sank, but was later recovered and pre-