The British airmen were at an atmospheric disadvantage. Straight in their face came the rays of the setting sun, while the calm sea beneath them was one blaze of reflected light. Against that blinding glare it was almost impossible to distinguish the mere black dot in the vast aerial expanse that represented the returning hostile aviator; while on the other hand the Hun, with the sun at his back, would be able to discern with comparative ease the glint of the seaplane's wings. The characteristic tick of the wireless brought. Kirkwood to attention. With the receiver clamped to his ear he took down the message and passed it on to his companion. "Our pigeon!" soliloquised Barcroft grimly. The information was to the effect that the "Hippodrome" had first sighted the approaching Hun machine by means of telescopes. The hostile craft had previously spotted two of the intercepting seaplanes, and her pilot, taking advantage of the light, decided to make a vol-plane to within a few hundred feet above the level of the sea. By so doing he was sacrificing his advantage of altitude, but there was a chance of slipping unobserved under the British aircraft. Once through the far-flung cordon he hoped to rely upon superior speed and climbing powers to elude pursuit. By this time Barcroft had "picked up" his opponent. At first sight it seemed as if the Hun were executing a nose dive. Keenly on the alert the flight-sub depressed the ailerons with a quick yet decided movement. There was no trace of jerkiness in the pilot's actions. All were performed with that smooth dexterity and rapidity that comprised the essential qualifications of a successful airman. At an aggregate speed of nearly two hundred miles an hour the rival aeroplanes converged. It seemed as if each pilot were bent upon ramming his opponent and sending the colliding craft to a common destruction. Barcroft, his hands resting lightly on the "joy-stick," was keenly alert to every forthcoming move of his adversary. Already the Hun observer was letting off rounds from his machine-gun in the vain hope that some of the hail of bullets would disable the British seaplane. On his part Kirkwood "stood by," ready at the first favourable opportunity to let the Hun have a taste of the Lewis gun--and the opportunity was not yet. Suddenly the German monoplane straightened out, then, lifting, attempted to pass above the seaplane. Quick as a flash Barcroft grasped the situation. Round swung the British machine, though not before a dozen holes had been ripped in her wings, as, banking steeply, she presented a vast spread of canvas to the hostile machine-gun. Through the turning movement of his opponent the Hun had gained nearly three hundred yards. The observer, swinging his gun aft, was busily engaged in fitting a new belt of ammunition.