Pursuit, Barcroft knew, was futile. Not only was the fugitive going in an easterly direction, which meant that had Billy held on in chase he would be lured further and further away from his floating base, but the Hun machine was more powerfully engined and possessed an undoubted superiority of speed. "By Jove!" shouted the A.P. "Fuller's planing down. He's got the old bus under control of sorts." The flight-sub looked downwards. A small rectangular patch of grey eighteen hundred feet down confirmed the truth of Kirkwood's statement. The injured seaplane was volplaning in wide circles. Her pilot was about to make an involuntary landing. This, in itself, was a highly dangerous performance, as the floats were very unsatisfactory landingskids. It was a hundred chances to one that the seaplane would bump hard and collapse, pinning the pilot under the wreckage. Even if Fuller escaped with his life or without broken limbs, he was confronted with the additional danger of being made a prisoner. Without a moment's delay Barcroft switched off the ignition and commenced a volplane. At least he would be able to discover whether his chum was able to make a safe landing. Beyond that-- "Good old Fuller!" almost yelled the A.P. "He's spotted a canal. I see his move--artful bounder!" Running in a direction approximately east and west was a long stretch of artificial water. The straightness of its course showed that it was not a river. It was bordered on either side by a broad tow-path, which in turn was fringed by a line of poplars. With the exception of a string of barges being towed down by a small tug (and they were nearly two miles away) the canal looked deserted. It was for this expanse of water that Fuller was making. Provided there was sufficient width for the extreme breadth of his wing spread and a margin to boot, there was little doubt of the experienced flight-lieutenant's ability to make a safe descent. "He's done it!" announced Kirkwood. "If he has managed it there is no reason why we shouldn't," thought Barcroft grimly. "Stand by, old man; we'll shove down and pick him up." The canal appeared to expand in size in order to meet the descending seaplane. It required all the skill and nerve at the youthful pilot's command to carry out his desperate plan. An error of a few feet to right or left meant irreparable damage to the frail craft and failure of his devoted efforts on behalf of his stranded friend. With admirable judgment Billy brought his "bus" down, making a fine "landing" on the surface of the canal at a distance of less than a hundred yards from the crippled aircraft, Then, drifting gently, the seaplane brought up alongside the bank, with one of her floats rubbing against the edge of the tow-path. "Nip out and hold her on, old man!" exclaimed Billy. The A.P. obeyed promptly. Fortunately this required little or no effort, for the thick-set though leafless trees broke the force of what wind there was.