The _A-1_ was engaged in manœuvers off Spithead, England, when she rose to the surface right under the bows of the fast-steaming Union Castle Liner _Berwick Castle_. Before anything could be done, the sharp prow of the steamer had cut a great gash in the thin hull of the submarine and sent her to the bottom with all her crew. This was in broad daylight; her sister-ship _C-11_ was rammed and sunk by another liner three years later, at night. The _Pluviôse_ of the French navy escaped the bow of an on-coming cross-channel steamer when the submarine came up at the entrance to Calais Harbor, only to have her topsides crushed in by a blow from one of the paddle-wheels. Collisions like these are less likely to happen nowadays, for the navigating officer of a modern submarine can take a look round the horizon through the periscope from a depth sufficient to let most steamers pass harmlessly over him, and in case of darkness or fog, he can detect the vibrations of approaching propellers by means of the Fessenden oscillator or some similar device. Yet the frequency with which submarines have been intentionally rammed and sunk in the present war shows that they would still be liable to rise blindly to their destruction in time of peace. 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.