"Phew!" he muttered. "Too jolly thick. It is a case for a smoke-helmet."
Back went the boat, returning in a short space of time with the required article. Donning the safety-helmet, one of the bluejackets descended, groped his way to the nearest hatchway and opened it.
An uninterrupted current of fresh air ensued, and in ten minutes the midship portion of the prize was practically free from noxious fumes.
"Blow me, Nobby," exclaimed one of the carpenter's crew, "did you ever see such a lash up? Strikes me they slung this old hooker together in a bit of a hurry."
The shipwright's contemptuous reference to the Teuton constructor's art was justified. The submarine had every appearance of being roughly built in sections and bolted together. Everything pointed to hurried and makeshift work.
Under the engine beds Sefton discovered two unexploded detonators. The one that had gone off was "something of a dud", for the explosive force was very feeble--insufficient even to start any of the hull plating. But it had performed a useful service to the British prize crew: the blast had detached the time-fuses from the remaining gun-cotton charges, and had thus preserved the submarine from total destruction.
Nevertheless Sefton heaved a sigh of relief as the two detonators were dropped overboard. Guncotton, especially German-made stuff, was apt to play peculiar tricks.
The fore and after compartments or sub-divisions of the hull were closed by means of watertight doors in the bulkheads. The foremost was found to have four feet of water--the same depth as that of the sea over the bank on which the vessel had stranded. It was here that the plates had been started when the U boat made her unlucky acquaintance with the Haisborough Shoal.
Flashing his torch upon the oily surface of the water, Sefton made a brief examination. On either side of the bulging framework were tiers of bunks. This compartment, then, was the sleeping-quarters of the submarine's crew. Of torpedo-tubes there were no signs; nor were these to be found anywhere else on board. Aft was a "gantry" communicating with an ingeniously contrived air-lock. The submarine was not designed for torpedo work but for an even more sinister task: that of mine-laying. Not a single globe of latent destruction remained on board. Already the U boat had sown her crop of death; would there be time to destroy the harvest?