But the task of the M.-L.'s was by no means accomplished. With the destroyers still holding on, in case a swarm of German torpedo-boats should issue from their lairs and pounce down upon the lightly-armed patrol-boats, No. 4452 and her consorts remained to watch for the returning seaplanes. With their customary inclination to make "a show", the "spotting" aircraft had gone inland upon the termination of the bombardment in the hope that a Hun airman or two would try conclusions in aerial combat. Failing an encounter, they proceeded with great deliberation to drop bombs upon certain railway junctions, aerodromes, ammunition dumps, and other objects of military importance. Over the placid sea patches of genuine sea-fog were stealing, as if Nature was bent upon showing man that, after all, his efforts at maritime camouflage were puny compared with hers. At intervals there was a clear view of the horizon; at others it was difficult to see a cable's length ahead. From the Belgian shore the thunder of the heavy guns had ceased, but the air rumbled with the distant ceaseless cannonade on the Ypres salient. There was no mistaking the noise. For nearly four years the dwellers on the south-east coast of England and the seafarers in the vicinity of the Straits of Dover had heard it. By this time its monotonous rumble hardly raised a comment, save when at times it rose to a crescendo of hate. And yet that incessant rumble was the death-knell of thousands of the flower of the British Empire and its gallant Allies, and, no less, that of the Hunnish invaders. Out of a broad patch of clammy fog glided M.-L. 4452 into a blaze of perfect sunshine. The glass windows of her wheel-house were open, since the moisture rendered them almost like frosted glass. "Look!" exclaimed Branscombe. In his excitement he brought his hand down heavily upon the quartermaster's shoulder. "A Fritz; and we've got him cold!" There was no mistake this time. Porpoises and floating boat-hook staves might be taken for U-boats, but the long, low-lying hull of the German submarine and its twin periscopes could not possibly be mistaken for anything but what they were, She was running on the surface at a moderate speed of ten knots, as if loath to "crack on" into the bewildering fog-bank that lay athwart her course. "Stand by, aft!" shouted the Sub.