for the best part of the next five weeks adverse climatic conditions prevented the salvage of the stranded sea-plane. unless given remarkably fine and calm weather, the sand-dunes of thorbury, fringed by extensive shoals carrying less than a fathom of water, were inaccessible.

christmas was drawing on apace, and the prospect of liberal leave demanded a "settling up" of the matter of the sea-plane as soon as possible. having received his instructions either to salve or destroy the errant machine, derek proceeded to thorbury in a brand-new motor-boat fitted with a powerful paraffin engine, and capable of keeping the sea in almost any weather. compared with the earlier motor-boats to which derek had been accustomed, r.a.f. 21, as she was officially designated, was a ship. with sleeping accommodation for two officers and four men, and fitted with a small but efficient galley, she was practically independent of the shore in the matter of sleeping and feeding her crew.

rounding thorbury head, r.a.f. 21 very cautiously approached the coast, keeping her lead-line going continuously. at a fathom and a half she anchored. it would be unwise to proceed farther in; even then the shore was only four hundred yards away.

manning a dinghy derek went ashore. it was a difficult matter, for the ground-swell was breaking heavily.

a brief examination of the sea-plane showed that her days were over. "beach-combers" had already been at work, and several of the metal fittings had been stolen. it was also evident that an attempt to launch the sea-plane through the surf would meet with failure.

"she'll have to go," declared derek to kaye, who had accompanied him. "i'll send off for some petrol."

the crew set to work to remove the floats and dismantle the motor. this done, the fuselage was drenched with petrol and set on fire. in a quarter of an hour nothing but a few charred struts and tangled tension-wires remained.

finding that it was impracticable to remove the floats—each of which weighed two hundredweight—except by land, derek returned to make his report. his next task was to proceed by motor-lorry and bring the remains back to the depot.

laden with a dinghy, two coils of three-inch rope, some "internal iron-bound blocks" (otherwise large pulleys), and nine men under derek's orders, a large motor-lorry left sableridge for thorbury. the day was a perfect one, and the men were in high spirits, for the "stunt" promised to be of the nature of a picnic. in forty minutes the ponderous vehicle had covered the twelve miles between sableridge and thorbury, then further progress was barred by soft, yielding sand.

between the lorry and the floats were first a stretch of fairly deep water forming part of thorbury harbour, and then three hundred yards of hummocking sand covered with coarse grass. the dinghy was unloaded, and the men and gear ferried across. round one of the floats was passed a long rope, and all hands, tailing on to the slack, began to haul away. the result was rather surprising, for directly the heavy mass began to move half a dozen large rats scampered from the interior of the float.

foot by foot, yard by yard, the float was man-hauled to the shore of the harbour, where, in sheltered water, it was launched and anchored until the second float was treated in a similar manner.

by this time the tide was ebbing with considerable strength, its rate exceeding five knots. the danger arose of the unwieldy craft being carried out across the bar to the open sea, and it was only by dint of hanging on to fifty fathoms of rope that the men could keep the floats in check. during these operations one of the floats capsized in the rollers that were sweeping in over the bar, and before it could be righted derek and half a dozen of his men had their sea-boots filled with water.

at the nearest point to the lorry where the floats could be grounded was an expanse of a hundred yards of soft sand. all the man-power at derek's command was unable to drag the floats up the gradually-shelving incline, nor could the lorry be brought any nearer by reason of the yielding nature of the sand.

"proper marathon, eh, what?" remarked derek, wiping the perspiration from his forehead.

"pity we hadn't burnt these as well," rejoined kaye. "already these salvage operations cannot have cost a penny less than thirty pounds, and in the end these blessed floats will be sold for as many shillings to some blighter who wants them for fishing-punts."

"service, my impatient lad; service with a big s!" exclaimed derek laughingly. "the main point is, we've got to bring these wretched floats back to the depot. i'm going to try hauling them up by means of the lorry. s'pose it's man enough for the job."

accordingly a sufficient length of stout rope was lashed round one of the floats and also to the lorry. at the signal the powerful vehicle began to move slowly ahead, and, with hardly a hitch, the float slithered over the sand up the incline and on to the hard ground. the second float followed suit, and then came the task of loading up.

by the time the two floats, the dinghy, and the gear were piled upon the lorry there was precious little room for eleven persons, but the royal air force men were not to be deterred by trifles. swarming all over the small mountain of gear, and even perched upon the canvas awning, they returned tired but triumphant. at last the work of salvage was completed, although the actual amount of material recovered was but a moiety of the original sea-plane.

upon entering the ante-room of the mess derek and kaye encountered grainger, lieutenant and hydro expert. grainger was in high spirits. his particular task was to get a hydro-glisseur into running order before he proceeded on christmas leave, and in spite of numerous difficulties he had achieved his end.

"the priceless old thing has been running this morning," he declared. "i'm taking her for a spin up to fisherton. coming, you fellows?"

"right-o!" replied derek. "hang on half a minute until i change my socks and sea-boots. i'm carrying about a quart of sea water in each boot, and it's beginning to feel slightly damp."

the hydro-glisseur, as its name implies, is a weird sort of craft that skims on the surface of the water and is propelled by a two-bladed aerial propeller. the body consists of six floats lashed together in pairs. credited with a speed of fifty knots, hydro-glisseurs are used for towing aeroplane targets at high speed, while air-craft hovering overhead try their level best to bomb the targets into fragments.

"you'll want your flying-kit, you fellows," declared grainger, as the trio prepared for the trial trip. "unless you want to be as deaf as posts, don't forget your helmets."

arrayed in leather jackets, flying head-dress and fur-lined gloves—gear that took derek's thoughts back to those seemingly far-off days at torringham aerodrome and on the western front—the "glisseurs" made their way to the boat-sheds out of which the freak craft were moored.

a few minor adjustments, and the powerful engine fired. throttled well down, the motor was running at sufficient speed to make the propeller buzz as it cleft the air.

"all ready? let go!" roared grainger.

a touch of the controls, and the glisseur gathered way. soon she began to lift under the enormously powerful drive of the huge propeller, until, with a deafening roar that could be heard for miles, the freak craft quickly worked up to a speed of certainly not less than forty-five knots.

presently grainger throttled down.

"there's a boche submarine alongside fisherton quay," he announced. "she came into harbour at lunch-time. i vote we go and have a look at her."

the proposal met with unanimous assent, and a course was shaped for the place where the ex-german submarine was moored.

as the hydro-glisseur approached the quay the speed was greatly reduced. derek could see the long, unlovely above-water outlines of the u-boat, her deck literally packed with people while from her mast floated the white ensign over the discredited emblem of the badly-bruised mailed fist—the black cross of hunland. for yards either way beyond the submarine the quay was lined with hundreds of interested spectators, for the trophy had been sent for public inspection, a small charge being made, and the proceeds given to local charities.

the mayor of fisherton, accompanied by the members of the corporation, was engaged upon an official civic welcome to the surrendered u-boat. there were aldermen and councillors in blue and scarlet robes, in cocked-hats and "top-hats". their wives, sisters, cousins, and aunts helped to swell the throng; while the gorgeously-attired mace-bearer and the portly town-crier, with his silver-plated bell, contributed their share to the splendour of the occasion. in the wake of the spectators was the town band; the musicians, having just completed a patriotic selection, were partaking of refreshment.

"mind how you come alongside with that gadget of yours," sung out the lieutenant in command of the submarine. "we've a terrific lot of camber, you know. if i were you i'd tie up alongside the quay. i'll show you round if you like, but there's a fine old crush already."

"we'll accept your invitation another day, thanks," replied grainger, as the hydro-glisseur, with the ignition switched off, glided slowly and silently with the tide. "nip ashore, kaye, and make that rope fast!"

moored stern-on to the granite wall of the quay, the hydro-glisseur bid fair to attract even more attention than the u-boat. even the mayor and corporation delayed their departure to gaze upon the marine freak; while perspiring policemen strove in vain to keep back the fisherton townsfolk and prevent them from unduly crowding upon the mayoral party.

"this is our little stunt," remarked grainger. "evidently people are curious to see us start up. we won't disappoint them. stand by, kaye, to cast off, but don't slip till i give the signal."

suddenly the buzz of conversation on the quay was absolutely drowned by the appalling and deafening roar of the powerful engine and the deep bass hum of the whirling propeller. the next instant almost every hat in the wake of the rapidly-revolving "prop" was torn from it's owner's head and whirled aloft in the tornado-like back-draught. scarlet and violet gowns flapped in the terrific blast like clothes hung out to dry on a boisterous day. in ten seconds a section of the crowd was swept aside like a portion of a cornfield falling under the action of a tractor reaper, while those of the spectators who were beyond the danger-zone rocked with merriment and shouted encouragement to the marathon competitors for the runaway head-gear.