. "Now there'll be trouble for
us. Schwalbe will certainly have a shot at recapturing us after the
battleship has cleared off. Why doesn't she settle U75, I wonder?"

The lads both expressed astonishment that the motionless unterseeboot
had escaped the attention of the super-Dreadnought's quick-firers. It
seemed as if the latter were ignoring U75 altogether and was sheering
off at full speed.

Suddenly Ross gave a whoop of delight, which ended in his swallowing a
mouthful of salt water. The _Tremendous_ was turning once more, and
heading straight for the doomed submarine.

[Illustration: "THE _TREMENDOUS_ WAS HEADING STRAIGHT FOR THE DOOMED
SUBMARINE"]

Mentally Ross compared the on-coming battleship with an express train,
as shown on a cinematograph screen, in the act of approaching the
audience. At one moment the ship was visible from her water-line to
the truck of her top-mast; at the next her bulk had suddenly expanded
and seemed to fill the complete field of vision. It looked as if the
two lads, in spite of the distance they had put between themselves and
the motionless submarine, would yet be in the way of the vengeful
battleship, whose extreme beam was not less than ninety feet.

Yet neither of the two chums made the slightest effort to swim farther
away. Mechanically treading water, they waited and watched.

They could see the terror-stricken attitudes of the crew of the doomed
U75. They heard the shouts of consternation as the massive steel bows
bore down upon her. Then, in a second it seemed, there was a hideous
crash that outvoiced the yells and shouts of despair as the
unterseeboot was rent in twain.

Of what happened during the next minute the lads had but a very hazy
idea. Caught by the irresistible bow wave as the _Tremendous_ tore
past, they were hurled aside like feathers and buried a couple of
fathoms down under the breaking, foaming mass of water. Vaguely they
heard the whirring of the four propellers--very near, it seemed; then,
caught by an eddy caused by the cavitation in the wake of the monstrous
vessel, they were separated and flung to the surface, half-breathless
and dazed.

Ross opened his eyes. The _Tremendous_ had already covered nearly a
quarter of a mile. Twenty yards away he saw his chum's head, as
Vernon, puffing like a grampus, was striking out towards him.

Where the submarine had dived for the last time was an ever-widening
circle of oil. Those of the German c