The vapor from a leaking fuel-tank, making an explosive mixture with the air inside the submarine and set off by a spark from the electrical machinery, has caused many accidents of another kind. Such an explosion took place on the original _Holland_, shortly after she was taken into the government service, but fortunately without killing any one. As the crew of the British _A-5_ were filling the fuel tanks of their vessel with gasoline, some of them were blown up through the open hatchway and into the sea by a burst of flaming vapor that killed six men and terribly injured twelve more. A rescue party that entered the boat to save the men still left aboard had several of its own members disabled by a second explosion. The vessel itself, however, was almost unharmed. But not long afterwards, another submarine of the same ill-fated class, the _A-8_, was lying off Plymouth breakwater with her hatches open, when the people on shore heard three distinct explosions on board her and saw her suddenly submerge. Her crew evidently got the hatches closed before she went down, as they sent up signals that they were alive but unable to rise. Two hours later a fourth explosion took place and all hope was abandoned.
This danger has been guarded against by better construction of tanks and valves, and very greatly lessened by the substitution of the heavy oil used in the Diesel engines for the more costly and volatile gasoline.
Besides igniting explosive oil vapors with their sparks, the old-fashioned sulphuric acid and lead storage batteries still used in many submarines are a great source of danger in themselves. The jars are too easily broken, and the leaking acid eats into the steel plating of the boat, weakening it if not actually letting in the sea water. And if salt water comes in contact with a battery of this type, then chlorin gas--the same poisonous gas that the Germans use against the Allies’ trenches--is generated and the crew are in very great danger of suffocation. The new Edison alkali storage battery, besides being lighter and more durable, uses no acid and cannot give off chlorin when saturated with sea water.
A, Running on the surface; B, In awash condition; C, Submerging; D, Exposing periscope; E, Fully submerged; F, Resting on the bottom.]