"Hedgeby!" came, indignantly, from Mr. Hartley, who had approached unnoticed. "What do you mean by chaffing these American officers so outrageously." "Must 'ave mistook my horders, sir," returned Hedgeby, saluting his commander. "Some blooming bloke told as 'ow these gentlemen wanted to be treated like pals." "The fault is mine, I guess," admitted Mr. Hartley, turning to Darrin and Ormsby. "These men are always chaffing each other, and they thought you wanted some of the same thing." "We don't object," Dave smiled. "If hot air is the motive power that drives these men, then we want to sample it." Hedgeby regarded this last speaker with a puzzled expression. "If you're talking about fuel, sir," he went on, as Mr. Hartley moved away, "Hi'll say that 'ot air engines wouldn't be no good wotever on these 'ere craft. Gasoline is what we use, mostly, for our engines, sir, though some of the biggest use petroleum." "Hot air is furnished by the men themselves," Dave explained. "It's a favorite fuel at sea." "Maybe, sir, maybe," admitted Hedgeby, slowly, looking as solemn as an owl. "Of course you know, sir, wot's used on the Yankee boats, anyway, sir, and if your Admiralty recommends 'ot air then no doubt hit's because you Yankees know 'ow to use it better than other fuel." "And the joke of it is," muttered Ormsby, as Hedgeby sprang to obey an order, "one can't tell whether a chap like that is laughing at us, or trying to sympathize with our ignorance." Dave laughed, then soon forgot the chaffing, for he was greatly interested in what he saw of the work that was being carried on. Certainly, for such a comparatively slow craft, a large area of sea surface could be covered in a forenoon. Presently Hedgeby came back to them, and Ormsby tried once more to extract some real information. "With the amount of speed you can command," he resumed, "what does a craft like this do, Hedgeby, if a German destroyer comes racing along after you?" "We just shut off speed, sir, and the blooming destroyer goes by so fast that nine times hout of ten she doesn't see us at all." "But if the destroyer sees you and stops to engage, what then?" Once more the quizzical expression faded from the British sailorman's eyes. He stepped back, resting one hand on a light gun mounted on a swivel pedestal. "We do hour best with this piece, sir." "An unequal combat, Hedgeby!" "You may well say it, sir, but hat least we come hout of the fracas as well as does the submarine that our sweep locates on the bottom." "Have you known of any case in which a mine-sweeper had any show at all against a German destroyer?" "Yes, sir; this very craft was the boat, sir. The destroyer 'eld 'er fire and come hup close, sir, to 'ave fun teasing us. Only one shot we fired, sir, from our after gun, at the houtset, sir, but that one shot carried away the destroyer's rudder just below the water line. It was hall a piece of luck, sir."