At six bells (11 a.m.) the Capella, having replenished her fuel and stores, and made good slight defects, was "tracked" out of the dock. An hour later she left Southampton, bound for a rendezvous off Beachy Head, near which a U-boat had been reported to have made an unsuccessful attack upon a swift merchant vessel.
The run down Southampton Water was necessarily performed at quarter-speed, for in spite of her light displacement the Capella's wash at full speed was almost equal to that of a liner. Even as it was, a long line of white foam lashed itself upon the mudflats several minutes after she had passed.
When Calshot Castle was abreast, speed was increased to 30 knots. There was an easterly breeze blowing against the ebb-tide, with the result that quite a choppy sea was met with outside Southampton Water. Like a knife, the sharp cutwater of the Capella cleft the waves, sending up showers of white spray; but such was her speed that, before the wind could carry the spindrift on deck, the swift vessel was beyond the cascade of foam. She hardly felt the motion of the waves; indeed, she was so steady that it was possible to place a pail of water on deck without any of the contents being spilt by the "lift" of the ship.
Under the guidance of Noel Fox, the midshipmen made the round of the vessel, the Sub explaining everything to them in detail. Already the lads had taken a great fancy to the Sub, and Fox reciprocated the sentiment. He had a way about him that enabled him to give particulars of the most intricate mechanism without having to resort to dry, parrot-like instruction.
By the time he had explained the ingenious devices used to entrap the German unterseebooten, Ross and Vernon felt inclined to marvel how it was they found themselves on board the Capella, since only sheer good luck had saved U75 from being doomed during every hour of their brief and involuntary detention.
"Yes, we can mop up the German submarines quicker than they can turn them out," said the Sub. "Of course I don't mean to say that a few of them won't get a smack at some of our ships for some time to come; but all the same we are giving them beans. From a strictly professional point of view we would be sorry if Old Turps abandoned his 'effectual' blockade. Our chances of having a high old game with the unterseebooten would be considerably reduced."
"There are still some in the English Channel," hazarded Vernon.
"Yes, a few; but have you noticed how those fellows fight shy of Dover? They shun it like the plague. It's horribly unhealthy for them. D'ye know why? Perhaps you wouldn't have paid much attention to it, but some months ago the Admiralty issued a 'Notice to Mariners', stating that the Straits of Dover were heavily mined, and that all shipping was to pass through the Downs within three miles of the Kentish coast.
"So it's fairly safe to assume that the few stray unterseebooten that are still lurking in the Channel have made the passage round the north coast of Scotland. It's only a matter of time before we bag the lot, I fancy."
"And our submarines?" enquired Ross.
"Have fewer opportunities since the Hun battleships and cruisers have such a decided inclination to remain in harbour," rejoined Fox. "When there's a chance, you can bet your bottom dollar that our fellows seize it. Quite recently one of our submarines found herself alone and disabled in the Bight of Heligoland. Undismayed, her lieutenant-commander signalled to a passing German trawler, covered her with his guns, and made the Hun tow the crippled submarine into British waters. Then he released his involuntary benefactor, but before so doing can you guess what he did?"
"No," replied both lads.
"Made the Huns line up on deck and sing the 'Hymn of Hate'. You can imagine the surprise of the trawler's men, who, judging by the treatment meted out to our fishermen by the German submarines, expected nothing less than imprisonment and the loss of their boat. But it's close on one bell," remarked Fox at length. "You're messing with the skipper to-day, I believe. He's quite a decent sort when you know him properly, but it takes a bit of doing."
A seaman strode up to the bell and gave it a sharp stroke. Just then a messenger hurried from the diminutive "wireless" room abaft the chart-house and, leaping down the ladder at a single bound, knocked at the door of the Captain's cabin.
"Stow those things away, Sparkes," exclaimed Captain Syllenger. "Lunch will have to wait."
He dashed out of his cabin. On the way to the bridge he passed Fox and the two midshipmen.
"You'll have to tighten your belts, my lads," he announced. "We've just had a message through. A strafed unterseeboot has been spotted trying to get into Spithead. If we don't nab her within half an hour, I'll eat my hat!"
CHAPTER XVII. A Double Bag
It was a sea-plane, flying at fifteen hundred feet above the Warner and The Nab Lightships, that had detected an elongated shadow creeping stealthily over the shingly bottom close to the Dean Tail Buoy. The shadow was that of a German unterseeboot, since none of the British submarines were known to be in the eastern approaches to Spithead. Evidently she had gone out of her course, for instead of being in the main channel she was well to the north of it. More than likely the strong east-going tide, which hereabout surges at such a rate that it causes the shingle 30 or 40 feet beneath the surface to emit a deep rumble, had taken the unterseeboot in its grip.
Promptly the sea-plane wirelessed the news, and quickly a "general call" was sent to the patrol vessels in the vicinity. The Capella was one of the craft that picked up the welcome order.
She was now only seven sea miles distant from the Dean Tail Buoy. Within ten minutes of the receipt of the wireless she was on the spot—one of the very first of a regular hornet flotilla bent upon adding yet another of Von Tirpitz's pets to the "bag".
For the next quarter of an hour it looked as if a novel kind of marine waltz was in progress. Nearly a score of swift vessels were executing fantastic movements at full speed, circling and interchanging positions until it seemed as if collisions were impossible to avoid.
Their object was to thoroughly bewilder the already doomed U-boat, for, if possible, her capture in a practically intact condition was desired. In very deep water, salvage of a sunken submarine was out of the question; here, in a comparatively shallow depth, and close to an important naval base, to which the prize could be taken with little trouble, the opportunity for capture rather than instant destruction was too good to be missed.
Suddenly a cloud of white smoke shot up from the sea. Its appearance was greeted by hearty cheers from the patrol vessels. It was a signal that the U-boat, in her attempt to find deep water, had floundered blindly into the trap. Over and over again the hunters passed, towing non-explosive grapnels, until it was certain that the prey was helpless in their toils.
Then, in obedience to an order from the senior officer, the swift vessels withdrew for nearly three cables' length from the spot where the boat lay. Two slow but powerfully engined trawlers approached at a cable's length abreast, towing the bight of a massive steel hawser between. Doing little more than drift with the tide they crept past the submerged U-boat, one on either side of the mark-buoy that indicated her position.