Page:Popular Science Monthly Volume 88.djvu/683

 Popular Science Monthly

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��water; if that should come into contact with the liquid of the battery, chlorine gas — the poison gas of European battle- fields — would fill the vessel.

Although the Edison cell will not generate chlorine, even if salt water should leak in, it does generate an ex- cessive amount of hydrogen when dis- charging. Whatever type of cell may be installed the storage battery is heavy, cumbrous, dangerous and very limited in the amount of power that it is able to deliver.

Realizing that the submarine must be freed of tht, storage battery, the Na\^ Department has taken a great interest in

��Open superstructure

��company spent about $130,000 m com- pleting a submarine boat, seventy-five feet long and seven and one-half feet in beam. It was driven only by oil en- gines; it had no storage batters' at all. In order that the crew might live despite the poisonous gases given off by the en- gines, a compressed air ventilating sys- tem was installed. The six men on board stayed under water thirty-six hours — a record submergence.

It was in this boat that Mr. Neff be- came interested. He made improve- ments of his own and engaged engineers to contribute their ideas. A trial board appointed by the Na\^ Department ap- proved of the ventilating and propulsion

����minutes — a feature of importance when the submarine is cruising at the surface in a heavy sea and the atmos- pheric air-feed may be cut off mo- mentarily.

The air bottles are tapped as they are needed. A high-pressure airline leads from these bottles throughout the vessel; the high pressure system in turn supplies a low pressure system of pipes. As soon as the atmospheric air-feeding devices have been cut off the air pressure within the vessel drops; and this drop is utilized to cause the feeding of air automatically from the stored supply.

The exhaust from the engine passes out through an exhaust manifold from which an rxhaust-pipe leads, discharging beneath the pro- pellers. iMechanical exhausters are also pro- vided in case the water pressure is so great that the natural suction effect produced by the travel of the vessel through the water is insufficient.

���wliat is known as the Xcff system of submarine propulsion, which takes its name from Abner R. Neff.

About three years ago a California

��system. The only objections which have been raised to the system are military in character. Against the Neff system it has been urged that large quantities of air would be emitted, when the submarine is running under water ; a wake of air bubbles would be left on the sur- face to betray the craft and to make it easy to follow its submerged course. An- other objection is the noise made by the Diesel engines under water; the pounding of engines and air compressors could easily be picked up by sensitive sound- receiving devices.

As might be supposed, the inventors of the Neff submarine system are ready with replies. They point to the manner of handling the exhaust from the en- gines — indicatcfl in a general wa\' in the accompanying illustration. The burnt gases are led to a system of condensing tubes outside of the hull. The expanded gases, having been condensed, are drawn

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