Throughout this month there had been great Zeppelin activity over the North Sea, for early in the year the German military craft had been handed over to the German navy, and the best airships of the two services had been concentrated near the German coast at Nordholz, Wittmundshaven, Ahlhorn, and Tondern. Until May 1916 the Zeppelins had carried out their patrols at a height of a thousand feet, looking for our mine-fields and scouting for our naval forces, but in this month L-7 was destroyed by gun-fire from a naval unit, and they were now, excepting on rare occasions, carrying out their work at a great altitude.
At four o'clock the mist began to lift; we went down to the shed, the engines were started, the crew climbed on board, and at five o'clock Billiken took the flying-boat off the harbour.
When he turned '77 out to sea and steadied on the course, Billiken saw below him through the mist, within the encircling arm of the harbour, the tall sheds of the station, the light cruisers and destroyers at anchor, the submarines nestling close to their mother ships, and the mine-sweepers disentangling themselves from their own particular crowded dock preparatory to beginning the day's work.
'77 in the mist.
He then glanced back down inside the hull of the boat, and saw Dickey busy with note-book and wind-tables working out the allowances, the wireless operator fingering his box of tricks as he tuned in with his shore station, and the engineer going over his petrol-pumps. This was the eighth time he had been out on a similar errand, but so far he had not been successful.
As he passed out of the approaches to Harwich the mist shut in; so he brought the boat down to five hundred feet, and fifteen minutes later he passed the Shipwash. This was the last thing he was to see until he sighted the Dutch Islands, and from this time on navigation was done by compass, dead-reckoning, and inspiration.
To a land-machine pilot a compass is an instrument in which he has no trust. It may show him the way over the lines and the way back, or it may not. It may apparently go mad, and swing round and round, or the north point may steady on anywhere but north.
But the flying-boat pilot has to rely on his compass. He uses a big one, and puts it in a place where it will not be affected by iron or steel; or if it is, and he cannot correct the error, he marks the errors on a card and sets it up where it can be seen. He understands variation, which is the difference between the true and magnetic bearing, and which varies all over the world, and at any one place, from year to year. And he can steer a course within two degrees.