All hope of shaking off the destroyer in the darkness was now at an end. North, south, east, and west the sky line was unbroken save by the grim outlines of the enemy craft. Every minute it was growing lighter, thus decreasing the slight advantage held by the patrol boat. It might be on this account that the larger craft was withholding her fire, for her guns were now silent; or, perhaps, the men rescued from the sea had informed the captain of the destroyer that there was another compatriot on the mysteriously captured boat.
The upper disc of the sun appeared above the horizon, a blood-red arc of fire. Farrar found himself wondering whether he was about to look upon the orb of day for the last time, yet, in spite of his resolution to fight to a finish, he mechanically put on a lifebelt which his companion had handed him.
A clanking sound from the motor-room, audible above the purr of the machinery and the throb of the pistons, roused the sub to a state of activity.
"Knocking badly!" he exclaimed. "Half a minute, Moke; I'll see what's to be done."
Even as he moved towards the hatchway there came an ear-splitting crash. The bows of the boat rose high out of the water, and subsided heavily in a smother of smoke and foam. A cloud of steam issuing from the motor-room indicated that an inrush of sea water had come in contact with the hot cylinders. The ignition failed, and the propellers ceased to revolve.
Then, with a sickening, shuddering movement the stricken craft heeled over on her side, with her bows level with the water. Momentarily recovering from her list, she slid beneath the surface, leaving the two chums floundering in a maelstrom of oil and foam.
"That's done it!" ejaculated the sub, addressing the well-nigh breathless Moke, who was choking and coughing from the effects of swallowing a mouthful of particularly greasy fluid. "What's that you're hanging on to?"
"Only the p-p-portmanteau," spluttered Sylvester. "It won't s-s-sink, dash it!"
The sub swam to his chum's side.
"We'll open it. The thing's watertight as it is," he said. "Won't do to let that fall into the hands of the enemy."