Once Kirkwood turned his head to watch the following seaplanes. Only one was in sight. The rest had already turned off for their respective objectives, and even that one was beginning to plane down towards a broad canal on which were dozens of loaded barges, their cargoes consisting of heavy gun ammunition destined for the batteries of Zeebrugge and Ostend. For the present the A.P.'s task was practically a sinecure. There was no necessity to use the wireless instrument: two hundred feet of trail ing aerial wire is apt to be in the way during bomb-dropping operations; besides, the raiding seaplane, not having to register for the guns of the fleet, could refrain from reporting progress until her return to her parent ship. So having made sure as far as possible that the bomb dropping gear was in working order this time, and having fitted a tray of ammunition to the Lewis gun in order to be ready for use in case of emergencies, Kirkwood leant over the side of the fuselage and contemplated the country beneath; the features of which as seen from the air he knew better by this time than any of his native land. From Ghent Barcroft followed the course of the River Scheldt until the town of Antwerp appeared in sight. At this point Fuller was observed to be turning away to the right. Both seaplanes were approaching their respective objectives. "Bestir yourself, you lazy bounder!" shouted Billy through the voice tube. "There's something ahead. Looks like a balloon. Get your glasses and see what it is." "It is a balloon," declared Kirkwood after a brief inspection. "A captive one." "And right over the Lierre hangars," thought the pilot. "What for? There's nothing to observe from a belligerent point of view, unless the bounders are expecting us. It may be that the balloon is in use for instructional purposes. If so, I'll give the young pups cold feet, by Jove!" "They've spotted us," announced the A.P. "They've begun to haul the thing down." "Then they are too late," added Barcroft grimly. "Gun all right? Stand by to give 'em a tray." Tilting the ailerons the pilot swooped down towards the unwieldy, tethered gas-bag. As he did so mushrooms of white smoke burst into view all around the descending seaplane. The German anti-aircraft guns were firing upon the British raiders. Barcroft held steadily on his course. He was quite used to shrapnel by this time. He knew, too, that soon the Hun gunners would have to cease fire for fear of hitting their own captive balloon. Already the German officers in the car of the balloon realised that it was impossible for the gas-bag to be hauled down in time. Three of them leapt into space. The fourth remained, grasping the edge of the basket-work and staring terror-stricken at the approaching seaplane.