tell-tale, that is a bank of miniature lamps, each of which is connected to a detector in a compartment. Now if the boat should spring a leak the detector closes the current and the lamp is hit.
Then there is another electrical system that closes all the bulkhead doors by electricity. The instant the tell-tale lamp lights up and shows that a compartment is leaking the commander presses a button which rings a bell in it and this warns any of the crew who may happen to be in it to get out; by throwing a switch the current operating the motors which work the bulkhead door is cut in and the door is screwed down watertight. Should a shell put the conning tower out of commission the boat can still be steered from the navigating room in her hull.
The power plant that drove the H-24 was a big 12-cylinder oil burning engine that developed, I should say, about 3,000 horse-power and it worked on the same general plan as a motor car engine. Now when the boat runs light or awash the engine drives her propeller direct and at the same time the engine runs a dynamo and this charges a large storage battery.
