ugh," declared the Leutnant. "Himmel, it is not enough to get
us round Cape Wrath. On board we have only sufficient for six hours'
surface running, while our batteries are not far short of running down.
You had better see the captain and explain."

Leaving von Ruhle to direct the seamen to the secret petrol store in
the cave, Ramblethorne accompanied the Leutnant to the submarine.

The U75 was one of the latest type of Germany's submarines. Over three
hundred feet in length, there was little about her in common with the
accepted idea of under-water craft. Her deck ran in one continuous
sweep for almost her entire length, and rose nearly six feet above the
surface. The visible part of her sides was perpendicular, the bulging
sections being entirely beneath the surface. Her conning-tower was
surrounded by a platform as long as the navigation-bridge of a modern
destroyer. The two periscopes were "housed", but two slender
"wireless" masts gave the boat the appearance of a swift torpedo craft.

Acknowledging a salute from a burly quartermaster, Ramblethorne gained
the deck, and was escorted aft by the Leutnant. Pacing the tapering
platform was a broad-shouldered, fair-haired man of about thirty,
although a carefully trimmed blonde beard made him look much older.

He lacked the natural elastic stride of the British naval officer. His
movements resembled those of a thoroughly drilled soldier, yet ever and
anon he would glance furtively in the direction of the open sea as if
in constant dread of sudden and unknown peril.

"Greetings, Herr von Hauptwald!" he exclaimed, when the Leutnant had
formally introduced his visitor. "You are well known to me by repute,
but I doubt whether we have met before."

"I fancy so," rejoined the doctor. "Do you not remember that little
affair in the Strauer Platz? Ah, I thought you would! But to come to
the point. We have been unable to obtain the requisite quantity of
petrol."

"Somehow I thought it," replied Kapitan Schwalbe. "How much have you?"

Ramblethorne told him.

"Enough, with what we have left on board, for only eight hundred miles
run. It will not take us home, and we are under orders not to leave
these waters before Friday next. We have been let down badly."

"I know that it is useless to express regrets," said Ramblethorne
boldly. "I can only hope that other means of supplying the requisite
fuel will be forthcoming. But here is another matter. We have ha