“It’s a position indicator. It would, I think, be useful at all times, but during fog it would be simply invaluable: that is, for coasting work, you know. It would be no good for protection against collision with another ship. But for clearing a headland or making a harbor in a fog it would be worth its weight in gold. The principle is, I believe, old, but I have been lucky enough to hit on improvements in detail which get over the defects of previous instruments. Speaking broadly, a fixed pointer, which may if desired carry a pen, rests on a moving chart. The chart is connected to a compass and to rollers operated by devices for recording the various components of motion: one is driven off the propeller, others are set, automatically mostly, for such things as wind, run of tide, wave motion and so on. The pointer always indicates the position of the ship, and as the ship moves, the chart moves to correspond. Steering then resolves itself into keeping the pointer on the correct line on the chart, and this can be done by night without guide lamps, or in a fog, as well as in daytime. The apparatus would also assist navigation through unbuoyed channels over covered mud flats, or in time of war through charted mine fields. I don’t want to be a nuisance to you, Mr. Cheyne, but I do wish you would at least let me show you the device. You could then decide whether you would allow me to fix it to your yacht for experimental purposes.” “I should like to see it,” Cheyne admitted. “If you can do all you claim, I certainly think you have a good thing. Where is it to be seen?” “On my launch, or rather, the launch I have borrowed.” The young man’s eagerness now almost approached excitement. His eyes sparkled and he fidgeted in his chair. “She is lying off Johnson’s boat slip at Dartmouth. I left the dinghy there.” “And you want me to go now?” “If you really will be so kind. I should propose a short run down the estuary and along the coast towards Exmouth, say for two or three hours. Could you spare so much time?” “Why, yes, I should enjoy it. I shall be back, say, between six and seven.” “I’ll have you back at Johnson’s slip at six o’clock. I have a taxi waiting now, and I’ll arrange with Johnson to call another for you as soon as he sees us coming up the estuary.” “I’ll go,” said Cheyne. “Just a moment until I tell my people and get a coat.”