When a bomb is released it travels forward on the same line as the machine, and, at first, at the same speed, but its speed forward gradually diminishes owing to the resistance of the air. At the same time it travels downwards owing to the force of gravity at an ever increasing rate of speed. It thus reaches the surface of the sea just after the machine has passed vertically over the spot. Therefore a bomb is released some time before the machine is vertically over the target, and this time is determined by the speed of the machine over the sea, the height at which it is flying, and the size, shape, and weight of the bomb. All these factors are worked out on the bomb-sight, and the bomb-dropper has only to pull the release-lever when two projections on the sight and the target are in line.
Holmes, in the front cockpit, looking over the sight and with his hand on the release-lever, waited.
The broad white wake behind the submarine began to diminish in length and width. The deck disappeared beneath a tumble of broken water. The conning-tower alone showed. And then the submarine dived.
It had all the air of performing a clever sleight-of-hand trick, and vanished with such lazy insolence that, arriving over the place where it had gone down one minute too late, our hearts were filled with astonishment and anger.
There was nothing to be done. "See you later," we said, and carried on, for we knew that the Spider Web would bring us back again to the same place, and we reasoned that the Commander of the submarine would say, "Here she comes, and there she goes," and would come to the surface shortly. There was no use waiting around the vicinity, for before Fritz came up he would search the air with a "sky-scraping" periscope, a periscope with the lenses so arranged that the whole arc of the heavens could be viewed.
Pushing on we sighted the Schouen Bank buoy in the distance through binoculars, and turned north up the Dutch coast. On the next two legs of the patrol, more or less parallel with the shore, we broke out the package of sandwiches and broached the thermos flask, taking this opportunity of having a drop of early lunch. Then after steering various courses as requisite, we again approached the position where the submarine had been first sighted.
She was sighted again three miles on the port bow, fully blown, her engines stopped, and the crew on deck enjoying a breath of fresh air. But now we were near enough to recognise her as of the U-B class, from the one gun mounted close before the conning-tower, the deck sloping down aft to the stern where it was awash, and the net-cutter mounted above the stem.
As we burst on towards the U-boat full out at a height of six hundred feet we could see puffs of smoke coming from the conning-tower. The crew were firing at us with a pom-pom.
And then I lost sight of the submarine.
But Holmes in the front cockpit, with his view unobstructed by the hull of the boat, could still see the submarine and guided me by hand signal.