Page:Collier's New Encyclopedia v. 09.djvu/172

LEFT SUBMARINES 138 SUBMARINES for the motors is supplied by storage batteries. An arrangement is made sim- ilar to that on the ordinary automobile (see "Electric Battery"), by which the storage batteries can be recharged from a generator driven by the Diesel or gaso- line engine when the boat is traveling on the surface. The newer types of cruis- ing submarines can travel upward of 100 miles on a single charge of the bat- teries. It will be seen, therefore, that even they can remain beneath the surface for comparatively short periods of time, even if other considerations permitted them to keep submerged for any greater period. One of the most difficult prob- lems which confronted early inventors was that of keeping the boat on an even keel. This is now accomplished by means of ballast tanks and horizontal runners, or by means of the gyroscope. But the matter still remains one which requires constant watchfulness. It will be clearly seen that under the conditions existing in a submarine, where the vessel is so to speak in a state of delicate balance, the moving of equipment or of torpedoes, and especially the discharge of torpedoes, presents problems of peculiar difficulty. As indicated above, the problems have to a large extent been solved, but the sta- bility of the submarine still leaves room for improvement. Submerging is ef- fected by admitting water into tanks specially designed for the purpose. Con- versely, the boat is brought to the sur- face by expelling the water from these tanks either by means of compressed air or with the aid of pumps. The speed with which a boat can submerge or rise has increased considerably in recent years, but even now it varies somewhat with conditions. On the average, from one and one-half to three minutes are re- quired for a boat to emerge sufficiently far from the water to use her guns. The periscope, by means of which the ob- serving officer can watch what is taking place on the surface of the water while the boat remains almost completely sub- merged, is an essential part of submarine equipment, and the principle of reflecting mirrors, on which it depends, is familiar to all. Submarines are costly to build; ton for ton they cost more than twice as much as surface battleships or cruisers. The pre-war cost was estimated at, ap- proximately, $1,000 per ton, but it is cer- tain that the cost of those built under war-time conditions was much higher than this. Submarine Merchantmen. — The first (and possibly the last) submarine merchantman was the "Deutschland," which crossed the Atlantic with a valu- able cargo of dyestuffs from Germany and reached the United States in July, 1916. She is believed to have had a sister ship known as the "Bremen," and this is supposed to have been captured or sunk by the British. The utility of the submarine for carrying cargo is ob- viously small. Its comparatively slow speed, its high cost of construction, its small capacity and its general incon- venience, render it not worth considera- tion as a cargo carrier. It is inconceiv- able that it will ever be used as such in the future, except by a country which finds itself situated as Germany was in the late war, with its main fleet impotent and its mercantile vessels swept from the seas. Previous to the European War there were many to be found, even among the highest authorities, who prophesied that the submarine had rendered the surface war vessel useless and impotent. In the early months of the war, when German submarines scored heavily against Brit- ish and French cruisers, it seemed as though their prophecies were to be ful- filled. As the power of the submarine grew, however, the means of fighting it grew more rapidly, and in the later years of the war almost its only success was against the unarmed or lightly armed merchantman. Deadly though it may be, the submarine, by its very nature, is vul- nerable. Many methods of destroying it were devised, some of which have become known, while others still remain secret. One of the earliest schemes was the con- struction of huge nets, two lines of which were placed across the Straits of Dover, from the coast of England to the coast of France, thus providing a compara- tively safe space between the two lines. The construction of the vast mine fields in the North Sea has already been dealt with in the early part of this article. Another device that was perhaps more dreaded by the submarine than any other was the "depth charge." This was a huge bomb, weighing 600 pounds or more. One or more of these bombs would be dropped from the stern of a destroyer where a submarine was last seen to sub- merge. They would explode at or near the bottom, and the enormous concussion would bring about the complete destruc- tion of the submarine. The hydrophone was another useful device invented dur- ing the war. This was a special type of telephone, by means of which the posi- tion of submarines could be detected by noises transmitted through water. These, and other devices, have greatly lessened the deadliness of submarines in legiti- mate warfare. None the less, they are still recognized as a powerful weapon of both defense and offense, and form an important adjunct to all modern navies.