Now the hum and drone that has puzzled us in the fog reveals itself as the note of a covey of seaplanes searching the waters ahead. They have come out at first sign of a clearing, and now fly low, trimming and banking in their flight like gannets at the fishing. A winking electric helio on one of them spits out a message to the leader of the destroyers, and she flashes answer and acknowledgment as readily as though the seaplane were a sister craft. A huge coastal airship thunders out across the land to join our forces. She grows to the eye as though expanding visibly, and noses down to almost masthead height in a sharp and steady-governed decline; abeam, she turns broad on, manoeuvring with ease and grace, and the sunlight on her silvered sides glints and sparkles purely, as though to shame the motley camouflage of the ships below. The commodore poises the baton as his ship draws up to her station. Till now we have steamed and steered 'in execution of previous orders' and, considering the dense fog and the press of ships at the anchorage and pilot-grounds, we have not been idle or neglectful. Now we are in sea order, and, with the ships closing up in formation, we attend our senior officer's signals as to course and speed. A string of flags goes up, fluttering to the yard of his ship, and we fret at the clumsy fingers that cannot get a similar hoist as quickly to ours. Anon, on all the ships, a gay setting of flags repeats the message, and we stand by to take measure and sheer of a tricky zigzag, at tap of the baton. The line of colour droops and fades quickly to the signalman's gathering; the convoy turns and swings into the silver-foil of the sun-ray. [Illustration: INWARD BOUND] XXI THE NORTH RIVER THE broad surface of the Hudson is scored by passage of craft of all trades and industries. Tugs and barges crowd the waterway in unending succession, threading their courses in a maze of harbour traffic; high-sided ferry-boats surge out from their slips and angle across the tide--crab-wise--towards the New Jersey shore; laden ocean steamers hold to the deeps of the fairway on their passage to the sea. Up stream and down, back and across, sheering in to the piers and wharves, the harbour traffic seems constantly to be scourged and hurried by the lash of an unseen taskmaster. The swift outrunning current adds a movement to the busy plying of the small craft--a hastening sweep to their progress, that suggests a driving power below the yellow tide. The stir of it! The thrash of screw and lapping of discoloured water, the shriek of impatient whistle-blasts, the thunder of escaping steam!