ly 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 u