Even supposing such to be the case, what fate was in store for the crew of this helpless machine? This part of the North Sea on which they had alighted was a sort of nautical No Man's Land. Fishing vessels gave it a wide berth, fearing the deadly and unseen menace of the mines. Merchantmen no longer followed the once busy maritime highway that led to the erstwhile prosperous port of Hamburg. Save for rare excursions on the part of the German torpedo flotillas and the occasional "sweeps" of Beatty's light cruisers and destroyers nothing afloat was likely to pass that way. Should the seaplane remain seaborne sufficiently long she might drift ashore, but from the direction of the wind it was pretty obvious that she would do so somewhere on the German Frisian group outside the southern portion of the chain of islands belonging to neutral Holland. The A.P. nudged his companion and tendered his cigarette case. Kirkwood was already smoking a pipe on the principle that he never knew when he might have a chance of another. Billy took the proffered cigarette and lit it. The tobacco seemed tasteless. With his lack of speech the flavour of the fragrant weed was denied him. Nearer and nearer came the smudges of smoke. The Huns were hard on the track of the crippled seaplane. Already Barcroft could distinguish the grey funnels just visible above the sky-line. "We must destroy our maps and documents," he wrote. "When I give the word smash the floats. Don't forget your air-collar." Fumbling in the locker the observer produced a pneumatic life-saving arrangement, which, when inflated, was capable of supporting its wearer for an indefinite time. Suddenly in the midst of the task of inflating the collar Kirkwood removed the tube from his lips. The air rushed out, and the rubber fabric collapsed like a punctured pneumatic tyre, while the A.P. stared with wide-open eyes at something not more than a hundred yards distant above the surface of the water. "A periscope, by Jove!" he exclaimed, making a grab at his maps and papers. They, at all events, had to be destroyed. Although his companion heard not a sound his attention was attracted by Kirkwood's manner. He, too, saw the spar-like object forging slowly ahead--so slowly that the cleavage of the water was insufficient to throw up the usual tell-tale feather of spray. Deliberately, almost human-like, the eye of the periscope turned slowly in a complete circle. The submarine, satisfied that there was no immediate danger to be anticipated, shook herself clear of the water, disclosing her conning-tower and a portion of the hull of one of the British G Class. Hardly able to credit their good fortune the flight-sub and his companion thrust their maps into their pockets and began to wave for assistance a quite unnecessary act since the lieutenant-commander of G 21 had already concluded rightly that the airmen were his compatriots in distress.