manned as they were by British seamen, whom the piratical Huns failed utterly to intimidate by threats of ruthless murder and sinking without a trace.

The short spring day was drawing to a close before the convoy weighed and shaped a course towards the frowning Bass Rock. Ahead steamed a destroyer, two more were on each flank of the long-drawn-out line, while astern, as a sort of whipper-in, came the Bolero, her turbine engines running at quarter speed.

As Officer of the Watch for the first watch Alec Seton had his work cut out. Almost every quarter of an hour the engine-room had to be telegraphed to, either to increase or decrease speed slightly, while the Morse flashing-lamp was practically in constant use, calling upon this vessel to close station or that to increase distance by so many cables.

And so the weary watch went on. The wind, hitherto off-shore, had suddenly veered to the south-east and blew with considerable violence right in the teeth of the convoy. Even at reduced speed the Bolero was "shipping it green" right over her raised fo'c'sle, while stinging showers of icy spray lashed viciously against the canvas dodgers and rattled like hail against the plate-glass windows of the chart-house.

There was a marked change in the Sub's appearance, as he crouched under the lee of the dodger. His hitherto slim figure looked podgy, and for a good reason.

Underneath his great-coat he wore his monkey-jacket, three sweaters, and a muffler. Oilskin trousers tucked into and turned over the tops of his sea-boots, and a weather-beaten cap rammed well down over his eyes completed his watch-keeping kit. With him stood the signalman and quartermaster, both enveloped in duffel suits.

On deck everything was battened down, for the glass was falling rapidly and giving every indication of a sharp, if short, blow before very long. Already the wind was moaning dismally through the wireless aerials, and causing the bridge canvas to bag in a double series of almost inflexible bulges.

At six bells (10 p.m.) the signal was given to the convoy to alter course eight points to port. Then ensued an anxious time, some of the vessels obeying with alacrity, others dallying in the carrying out of their instructions. With the wind now abeam, the lumbering craft rolled horribly, while the long, lean destroyers, which largely rely upon steadiness by reason of their speed, were constantly rolling rail under. Torn clouds of reeking smoke from the vessels to windward, mingled with icy spray, swept over the Bolero, whose position on that account was the most undesirable of the escorting craft.

"It's Fritz's chance, absolutely," thought Alec. "A U-boat could be lying awash a cable's length away and we shouldn't spot her. And it's a dirty night to have to stand by a sinking tramp."

"There's something on our port bow, sir," reported the look-out, stretching a glistening oilskin-enshrouded arm in the direction indicated.

"Yes, by Jove," ejaculated Seton. "It's a dirty Fritz. Starboard two, quartermaster, and let her have it."

It was for one thing fortunate that the Bolero was running at greatly reduced speed, otherwise the lurking U-boat might have been passed unnoticed.

The submarine had evidently been compelled to rise to recharge batteries, the heavy sea notwithstanding. Her hydrophones had given indication of the presence of the convoy, and the latter's recent change of course had set the vessels slightly abeam and at gradually reducing distance. The kapitan-leutnant of the U-boat, quick to grasp the situation, had waited until the escorting destroyers on the convoy's port hand had passed, and was now manoeuvring to fire a torpedo at the rearmost tramp—which also happened to be the largest. Owing to the darkness it was almost impracticable to make use of the periscope, so the German submarine remained awash in order to take a direct bearing on her intended victim.

In the shortest possible time the gun's crew of the for'ard 3-inch quick-firer were ready. At a bare two hundred yards the target was one that could not be easily missed and the gun-layer knew his job thoroughly.

Too late the astounded and terrified Huns sought to submerge. Before the last Teuton gained the quick-action watertight hatchway the Bolero's gun barked viciously. Fairly through the conning-tower at a height of a couple of feet above the tapering armoured deck the high-velocity shell passed. Exploding, it blew the top of the conning-tower to pieces, killing the kapitan-leutnant, the quartermaster, and two of the crew.

The doomed U-boat began to sink, clouds of oil-laden vapour issuing from the jagged base of the conning-tower; but even that was not enough. It is the practice of the U-boat hunters to make doubly sure.

At increased speed, and with slight port helm, the Bolero scraped past the up-tilted stern of her victim. Resisting the temptation to ram her with the destroyer's knife-like bows, Seton held on his course, while right aft a couple of petty officers were busily engaged in allowing a wire to run out. Attached to the wire was a powerful depth-charge—one of two ready for instant use.

Fifty—sixty—seventy—eighty fathoms, the P.O. brought his hovering finger down smartly upon the firing-key of the battery.

He performed the act without emotion, although it meant sealing the death-warrant of a score or more of human beings. To him it was merely the performance of duty: frequency of opportunity had made it matter of routine.

With a stupendous roar a column of water, showing greyish-white through the darkness, was hurled a couple of hundred feet into the air. The Bolero, as the tremendous wash created by the explosion met and overrode the crested waves, shook violently from stern to stem, while fragments of metal, hurled upwards to an immense height, fell all around her.

For some minutes it seemed as if the fury of the wind was subdued by the blast of displaced air, while astern the waves subsided in a rapidly-increasing circle under the influence of tons of heavy oil liberated from the shattered wreck of the modern pirate.

"Hard a-starboard, quartermaster!"

Alec's voice quivered with excitement. It was the first Hun that he had bagged, although the Bolero had claimed more than one before Seton had been appointed to the destroyer.

Telegraphing first for "half-speed", then "stop", and "half-speed astern", Seton brought her to a standstill almost in the centre of the vast patch of oil. As he did so he became aware of the fact that Lieutenant-Commander Trevannion, picturesquely rigged out in gaily-striped pyjamas, service cap, great-coat, and sea-boots, was standing beside him on the bridge.

"Good bag that," remarked the Lieutenant-Commander in dispassionate tones, as if Fritz-strafing was a less exciting occupation than hunting rats. "You've ordered the buoy to be let go, I see. Right-o, carry on!"

The nun-buoy, to which was attached a line terminating in a sinker, was dropped over the side to mark the position of the ill-fated Hun submarine, in order that divers could make subsequent examination, of the shattered hull, and fix her identity.

Meanwhile the Bolero had switched on her search-lights, and was sweeping the surface of the oily sea on the off-chance of sighting survivors. It was practically a matter of form, since previous experience told that rarely does a single member of a depth-charge-shattered U-boat live to tell the tale.

"Something on the starboard bow, sir," reported one of the lookout-men. "Looks like a corpse, sir."

Leaning over the bridge guard-rails Alec followed the direction indicated by the man's outstretched arm. Something black was floating on the sullen, oil-covered water. It was the body of a man clad in black oilskins, and wearing an inflated life-belt. Even as the Sub. looked, the man feebly waved his arm.

"Away duty boat!" shouted Seton.

There was an orderly rush to man the boat. Although the