Underneath this platform, with the observation holes barely six inches above the back of the curved deck, was the conning-tower. Above was the "navigating bridge," which could be removed if going into action. Here was the slight shelter, called by courtesy the chart-room, and two powerful searchlights.

Immediately abaft the bridge was a light telescopic mast for signalling purposes. Wireless "aerials"—always the bugbear of naval officers while overhead gear was in vogue—had been consigned to the limbo of the past, and receivers in the wireless room "picked up" the messages with unerring fidelity.

Abreast the mast were two seven-pounder automatic guns, protected from Maxim fire by light steel shields forming a complete turret. Abaft the mast, and twenty feet from the guns, were the two 21 in. torpedo tubes, taking an improved Whitehead with an effective range of five miles. From this point was a clear run of deck-space—save for the ventilating cowls and hatchways, that could be respectively unshipped or battened down should occasion arise—to the aft torpedo-tubes.

On the poop turtle-back was the supplementary conning-tower, and another eleven-pounder gun.

"All out" the Frome could do forty-three knots. With her, speed was the primary consideration. To minimise windage every object that it was possible to construct in that fashion was wedge-shaped—even the shafting of the ventilators, while with her after turtle-back deck the destroyer could go astern at twenty-one knots without fear of being swept by the waves. She carried a complement of ninety men, of whom only fifteen were "engine-room ratings."

Gradually the fog lifted, till the outlines of Southsea Beach could be followed almost as far as the mouth of Portsmouth Harbour; and now, with her speed increased to a modest ten knots, the destroyer slipped up the fairway against the surging ebb tide.

Just as the Frome was within a quarter of a mile from the Round Tower, where the entrance of Portsmouth Harbour is barely 250 yds. wide, a burst of sunshine dispersed the last vestige of the fog within the sheltered waters, though at Spithead the haze was as thick as ever.

"That's awkward, sir," remarked Fielding. Lieutenant Drake did not reply, but motioning the quartermaster to put the helm over to port, and telegraphing to the engine-room for fifteen knots, nodded significantly to his subordinate.

It was indeed awkward. Flying from the yard-arm of the naval station of Fort Blockhouse was the signal burgee letter S—a triangular blue and yellow flag—denoting that submarines were either entering or leaving Haslar Lake. From the Semaphore Tower, and from the foremast heads of all the ships in harbour, the Pilot Jack was flying, showing that one of H.M. ships was under way, and a glance astern showed that the second-class cruiser Vindictive was entering.

Right ahead came a huge battle-cruiser, with a Government tug lashed on either side, and a gaudily painted tug panting ahead with an enormous hawser, and a sister tender puffing decorously astern of the leviathan.

"That's a bungled bit of work," commented Drake. "She can't go back with this tide under her; and the Vindictive following us up, too. Pass the word for a warning signal to be sent to the cruiser, Mr. Cardyke. These fellows must be as mad as March hares."

The increased speed just saved the Frome from being in a very tight corner, for, hugging the eastern side of the entrance, she gained the broad expanse of the harbour just as the towed vessel came abeam.

Still Drake had to keep his full attention on his course; but the sub. and midshipman could devote themselves to the melancholy spectacle—for the Impregnable was on her way to the marine knacker's yard. Her days as an effective unit were judged to be over, and, sold out of the Service, she was on her way to a Dutch port to be broken up.

The Impregnable was one of the earlier "Dreadnought cruisers," and in her time held the palm for speed. She was of eighteen thousand tons displacement, and had attained a speed of twenty-six knots. Her armament consisted of eight 12 in. guns—one pair for'ard, another pair aft, and the others en échelon amidships—as well as a secondary battery of twenty-five 4 in. quick-firers. She had two tripod masts and tree huge funnels.

Very different the vessel looked from when, a few months previously, she had taken her place in the fleet at Spithead as an effective unit of the British Navy. Her topmasts were "housed," her boats and secondary armament removed, and her regulation coat of grey paint was streaked with rust and dirt. In her barbettes the 12 in. guns still grinned menacingly, but their teeth were drawn, their breech-blocks having been removed previous to sale.

"Seems like parting with an old friend," remarked the sub to Cardyke, for Fielding had served a commission on board of her. "To my mind, it's a mistake scrapping the older vessels so promptly. It's not my business to say so, of course; but still, that's my opinion."

"She'd do her little bit even yet," observed Cardyke. "She never has fired a shot in anger yet, has she?"

"No," replied the sub. "And she never will. We've seen the last of the old Impregnable, Cardyke."

But Sub-Lieutenant Paul Fielding was, for once, at least, hopelessly out of his bearings.

CHAPTER II

THE INTERRUPTED MATCH

The Frome came alongside the Fountain Lake Jetty, and her commander repaired to the commander-in-chief's office to make his report as to why the night gunnery exercises had not been carried out. To the relief of everyone on board the destroyer it was decided that the night-firing was to be postponed until after the little craft's refit, and in the interval the Frome was to lie alongside the jetty until her consort, the Blackadder, came out of No. 3 Dock.

"That's good!" ejaculated Fielding, as the officers went to dinner in the diminutive, cosy wardroom. "We'll have time to put in a few hours' practice at the nets. Have you seen the list of our team yet, Cardyke?"

"Thompson's sending out the names tomorrow. I know that we are in the team; Simpson gave me the cue," replied the midshipman. "The practice-nets will be available at ten o'clock to-morrow morning. I suppose we may go, sir?"

"Of course," assented Drake, good-naturedly. "The gunner will be in charge up to eight bells."

The four officers—for the engineer-lieutenant formed one of the party—fell to discussing everyday topics. "Shop" was rigidly tabooed in the Frome's wardroom unless absolutely necessary for Service reasons.

The following day, Thursday, passed almost without incident. Fielding and Cardyke put in a good morning's work at the practice-nets in the United Services ground; while Drake went ashore in the afternoon for a motor-drive.

Friday dawned bright and clear, with every prospect of a blazing hot day. Shortly after breakfast a newsboy brought off the daily papers to the ship, and for the next half-hour the officers "stood easy."

"By Jove! They think that something's happened to the old Impregnable," exclaimed Paul Fielding. "She ought to have turned up at the mouth of the Scheldt yesterday morning, and nothing has been seen or heard of her."

"Delayed by fog possibly," remarked the lieutenant-commander. "Still, it's no affair of the Admiralty's since the ship is sold."

"The paper hints at something mysterious."

"Naturally. There's