1. By Mechanical Means such as Clockwork, Springs, &c.—The Howell torpedo is driven by means of a heavy flywheel in the interior which is spun up to 10,000 revolutions a minute before discharging by means of special machinery. While all these methods are practicable they must be put aside as unsuitable owing to the slowness of the speed which a boat thus propelled can attain.
2. Compressed Air.—In order that a submarine may be driven at a high rate of speed for a considerable distance, such a large store of compressed air would have to be carried if this method were adopted, that little space would be left in the vessel for any other purposes. In addition to this such a store of compressed air would be a source of danger.
3. Manual Power.—The earliest submarines were of course driven by hand power, but no one nowadays would think of adopting this method.
4. Steam from Heated Water.—Mr. Nordenfelt propelled his boats beneath the surface by means of the steam given off by the heated water in the cisterns, and this was found sufficient for a distance run of 14 knots. He disliked accumulators, and this is not to be wondered at, for in his time they were very far from perfect; were he designing a submarine to-day, however, it is probable that he would choose electricity for sub-surface working.
5. Chemical Engines.—Dr. Payerne, d’Allest, and others, by means of a chaudière pyrotechnique, burnt, in hermetically closed furnaces, combustibles containing in themselves the oxygen necessary for their combustion, and got rid of the products of combustion by ingenious devices.
6. Electricity.—All modern submarines rely on an electric motor for under-water propulsion, the current being derived from accumulators. The ideal primary battery and the ideal accumulator are still to seek, but the latter improves yearly, and there is little doubt that some few years hence the current available will enable the submarine to make long voyages under water with greatly increased speed. It is said that the Holland has on no fewer than four occasions burned up the armature of her motor, and some device seems to be wanted to keep the armature cool.
7. Carbonic Acid.—Many attempts have been made to construct an engine which can be worked by liquid carbonic acid, but the general result, as some one has said, has hitherto been that the inventors have been more or less broken up in body and mind.
8. Liquid Air has been suggested as a propelling agent for submarines, but up till now it has not been applied for such a purpose. A motor-car propelled by liquid atmospheric air was shown at the Agricultural Hall in April last, and some energetic Americans are endeavouring to “boom” this elusive substance in this country. More sober investigators have, however, little faith in an immediate commercial future for liquid air.
INSIDE THE “GOUBET.”