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Page:Popular Science Monthly Volume 89.djvu/243

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��Another feature of the cargo-carrjing boat is the pro\ision of wheels whicii enable the craft to travel on the bed of the ocean, rivers and the like. Mr. Lake was the first to use what may be called "automobile submarines." Indeed his first \cnturc in the submarine field was the Argonaut, which ran on the bottom of Chesapeake Bay. The wheels are of great service in following a dredged

��rather in oil engines suitable for sub- marine purposes, lies somewhere in the neighborhood of two hundred horse- power per cylinder. The Germans arc now building submarine torpedo boats about two hundred and twenty- feet long, propelled by twin-screw engines aggregating two thousand, four hundred horse-power and giving a surface speed of seventeen knots. A submarine some-

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��Carry $1,000,000 Worth of Chemicals

��tight cylindrical tanks. The quarters for the crew, the engine room, etc., are contained in a water-tight cylindrical inner hull. When the vessel is to submerge, the entire space between the inner and outer hulls is flooded with sea water; when the vessel is to travel on the surface, the water is pumped out. The submarine boat has wheels, so that it can travel along the bottom of a dredged channel — a method of propul- sion which Mr. Lake has successfully employed. This huge submarine would be about 350 to 400 feet long. It would be not a submarine but a submersible ship

���channel. In some experiments which Mr. Lake performed for the Russian Government at Libau, some years ago, he was able to pick his way out of a harbor much more easily than com- petitors of his, simply by running along the bottom of a dredgecl channel.

There is no inherent difficulty- in build- ing a cargo-carrying submarine, even though it be four hundred feet long. But there is great difficulty in obtaining en- gines which will drive it.

The practical limit of size as yet at- tained in big submarine engines, or

��what bigger, requiring three thousand, six hundred horse-power to develop a surface speed that will enable her to be of any practical use will need three engines with si.x cylinders each. Now, for a \-essel four hundred feet long a very powerful set of propelling machines will be required. Oil engines are out of the question. Steam engines must be em- ployed. And the use of steam engines means the sol\-ing of the- very difficult problem of insulating the generating apparatus so that the crew will not be parboiled.

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