Although submerged, the submarine was "pumping" violently. Seasoned men were prostrate with sea-sickness. The air, in spite of chemical purifiers, was becoming almost intolerable. Everything movable was being thrown about in utter disorder, while to add to the discomfort of the crew the covering-plates of one of the lubricating-oil tanks had been strained, and at every jerk jets of viscous fluid would squirt through the fracture and trickle sullenly over the floor of the crew-space.
Since the watertight doors were still closed, Ross and Vernon were unable to get back to their bunks. Feeling thoroughly wretched, they were glad to accept Hans Koppe's offer to lie down on a long locker.
At noon, U75 came to the surface. The storm, being short forecasted, had quickly blown itself out, but the waves still ran high.
It was a prearranged plan on the part of the three U-boats operating in the English and Bristol Channels to communicate with each other by wireless at noon and at midnight. U75's wireless had a range of about 180 miles, and although it could be "jammed", the call could not be tapped by vessels other than the one for which it was intended. To make doubly sure, the messages were sent in code.
For nearly ten minutes U75 "made her number" without eliciting any reply. Perhaps it was well that Kapitan Schwalbe did not know what had happened to her consorts. U74 was at that moment lying on her side at the bottom of a Welsh harbour, her crew poisoned by the chlorine fumes from her batteries—the result of a rash curiosity on the part of her Lieutenant-Commander to investigate the approaches to the anchorage. As for U77, she was flying blindly for safety, with a couple of destroyers hard on her track, and a naval sea-plane overhead to direct them in their search.
Foiled in her efforts to get in touch with her consorts, U75 remained awash. The heave of the sea made it most difficult for her to use her periscope with certainty, for she had chosen a bad pitch on her ascent—the furious "overfalls" or "tide-rips" to the west of Lundy Island.
"We'll pay another visit to St. Mena's Island, Herr Rix," decided Kapitan Schwalbe, after the two officers had discussed the sinister matter of their futile attempt to make use of the wireless. "To-night at nine o'clock ought to suit. If we cannot get von Ruhle to see our signals—for my own part, I doubt whether he is in these parts—we'll have to do our best to get ashore. Meanwhile, keep a bright look-out. If we see any likely vessel coming this way, we'll try our luck once more."
"Message just received, mein herr," announced the wireless operator.
"From whom?" enquired Kapitan Schwalbe eagerly. He was devoutly hoping that either U74 or U77 had been able to "call up".
"I cannot say, sir," replied the man as he handed a code message to his superior.
Decoded, the "wireless" was as follows:
"Station 41 to unterseebooten. Two hundred gallons of fuel available here. Will be on the look-out for signals at 1 a.m."
The message was a "general call" for a secret petrol depot to any German submarine operating in the vicinity. Reference to the list of stations showed that "41" was at Port Treherne, a remote cove on the North Cornish coast about fifty miles from St. Mena's Island.
"I suppose it's safe," remarked Rix.
"With due precautions—yes," rejoined Kapitan Schwalbe. "At any rate, petrol we must have. Where's the chart? Ah, there we are! It looks a fairly easy place to approach, don't you think? The only danger from a navigation point is apparently this ledge of rocks—Lost Chance Reef, it's called. What unpleasant names these Englishmen give to their coasts!"
At that moment the Unter-leutnant, who happened to be at the conning-tower periscope, reported that a large vessel was bearing down towards them.
Kapitan Schwalbe hurried to the conning-tower. The object depicted was that of a modern tank-vessel about four hundred feet in length. She was low in the water, showing that she was well laden. In place of masts she had four stumpy poles supporting derricks. Right aft was the single funnel. The navigation bridge was well for'ard, connected with another bridge just in front of the funnel by a long slender gangway.
"An oil-tank homeward bound!" exclaimed Kapitan Schwalbe. "Just what we want to fall in with. All being well, there will be no necessity to visit either Port Treherne or St. Mena's Island. Ach! When we have taken what we require we will set fire to the ship, and the English will have a splendid view of a maritime bonfire."
The crew were ordered to their stations, the ballast tanks "blown", and U75 rose to the surface instead of "running awash", since the Kapitan had resolved to stop the tank by gun-fire.
Even then the waves were running so high that the guns' crews were almost constantly up to their knees in water.