ye, aye," was the prompt response.

"Board her, Herr Rix," said the Leutnant's superior officer. "Bring
back her papers with you. Order them to pump heavy oil both to
windward and leeward. We will then be able to run close alongside and
receive her hoses."

A boat containing two seamen and an apprentice was lowered from the
tank's quarter and rowed to the submarine. Into it dropped Leutnant
Rix and half a dozen armed men. With them they took two incendiary
bombs fitted with time-fuses.

Rix smiled grimly as he gained the oil-steamer's deck. The captain and
first mate were at the head of the accommodation ladder to receive him.
Most of the crew were already mustering on deck, each with a bundle
containing his private effects.

"You prize to German boat," announced the Leutnant. "Make you no
trouble and we you will not harm. First we will haf much
oil--petroleum, is it not? Order your engineer to get steam to
donkey-engine, and your men--the--the---- Hein! Ach, I haf it--the
hoses to get ready. When we fill up, then twenty minutes we give you
to clear out. You onderstan'?"

"Perfectly," replied the British skipper, a tall, raw-boned Scot, as he
eyed the podgy German Leutnant with grim contempt. "But d'ye ken yon?"

[Illustration: "'D'YE KEN YON?' ASKED THE BRITISH SKIPPER, AS HE EYED
THE PODGY GERMAN LEUTNANT WITH CONTEMPT"]

He pointed skywards. Less than five hundred feet up, yet sufficiently
far from the tank-vessel to enable the latter to screen her from the
unterseeboot, was a large naval sea-plane. It was to deaden the noise
of her motors that the ship's steam-pipe was continually blowing off
steam from the time that U75 made her peremptory demand.

The eyes of the Leutnant and his six men followed the direction
indicated by the British skipper's outstretched hand.

At that instant the sea-plane was visible above the towering sides of
the British vessel.

U75 was still forging slowly ahead. In a trice Kapitan Schwalbe
decided how to act. Ordering the men on deck to their diving stations,
he dropped agilely into the conning-tower and gave the word for the
helm to be ported.

Thus, while the quick-firers were being housed, the submarine had drawn
close under the oil-tank's quarter. Here she was comparatively safe
from the sea-plane, as the latter could not drop any bombs without risk
of exploding the highly inflammable cargo of the British vessel.

In ten seconds the sea-plane was ove