Until recent years naval authorities divided war submarines into two classes: Coast defense type of from 300 to 700 tons surface displace ment and cruising type of from 800 tons up with radius of 3,000 miles or more.
Submarine Construction and Equipment. —As may be supposed the apparatus and mech anism for such a complex condition of warfare must be very elaborate and complicated. The submarine's internal bewildering labyrinth of pipes, valves, gears, wheels, cylinders, etc., crowding the confined space is the wonder of those few visitors who are allowed an inspec tion of their interior workings. We will give a short review of the subject as described by such experts as M. F. Hays and others.
Hulls.— Submarines are built with double and single hulls. The latter have to be of con siderable strength to resist the pressure when submerging deeply, necessitating a circular or nearly circular cross section. They were of so-called spindle shape, both ends tapering to reduce the resistance in motion, but to obtain better sea-going qualities the bow and stern have been modified in recent cc -istruction. The Holland type has single and double hulls; the Labeuf type has an inner hull cylindrical with flat ends; this is enclosed entirely in an outer hull pointed at each end to reduce resistance in motion. The latter are used by the French, Aus trian and German (Krupp-Germania) navies.
Another type has single hull reinforced in parts by an outer construction as employed by the Italian, Portuguese and Brazilian navies and designed by Maj. Cesare Laurenti of the Fab brica Italiana Automobil Torino (Fiat), while the Dutch and Danish navies have used a corn posite hull designed by M. F. Hay. Other types have, of course, been developed.
Engines.— Steam soon had to give way to high-speed internal combustion engines. The first built for the British navy were fitted with four-cylinder vertical engines. Next came 16-cylinder Wolseley horizontal motors with 550 horse power; later, with increased dimensions they arrived at 850 horse power, giving 16 knots surface speed. The remaining defect was the noxious gas from the petrol or gasoline fuel, sickly as well as dangerously ex plosive, not to mention carburetor objection so well-known to aviators. Then came the new Diesel motor invention using heavy (crude) oils and all the above troubles were wiped out when the early slow-speed defects were over come. England used her first Diesel motor on submarine DI in 1907, developing 1,200 horse power. Its simplicity of operation, though complicated in mechanism, makes the Diesel engine (see INTERNAL COMBUSTION EN