"Thus suppose the machine to be diving; slackening these ropes, the pressure of the air underneath causes the flaps to open. As soon as this happens their inclination upwards tends to make the machine rise so long as the propellers are driving her forward, the angle of ascent being controlled by the angle to which they are allowed to open. If the machine inclines to lean over to right or left, the opening and closing of the flaps on one side or the other can be used to counteract it and restore the balance. With all kept tightly closed she can go forward or dive. With them open, and engines stopped, she dives quickly. The rudder is of box-kite form, and fastened to the after end of the cigar-like car, which apparently contains the engines, petrol tanks, etc., and enough air space to render the machine buoyant when water-borne. The propellers, which are placed on hollow shafts, whose bearings are supported on horizontal braces between the two V-shaped aluminium lattice girders attaching the planes to the car, are driven by separate endless chains, which come up out of the centre of the cylinder. They seem to be made either of aluminium, or more probably magnalium. "My drawing has rather exaggerated the diameter of the cylindrical car. There is a light wooden foot-board at either side, which also helps to steady the machine when on the water and two small floats at the end of the outriggers for the same purpose. There are also three small wheels fitted, I presume for facilitating ascent from dry ground. "KARL STRAUS." The spy laughed a low, hollow laugh of defiance. What could he say? He had been outwitted just at the supreme moment of his success. "I admit, my friend, that you were extremely clever in putting forward Goldstein as the spy, and thus misleading my friend Jacox," Ray said in triumph, as he laid his hand upon the rough sketch of the Kershaw invention. "But for a very timely discovery, too, my friend would have met with the terrible fate which you and your accomplice planned with such devilish ingenuity. So if you don't wish to be arrested for conspiracy and murder you'd better make yourself scarce out of England quickly." "What do you mean, Ray?" I cried. "I'll show you," he answered as he gathered up the whole of the spy's papers while the German stood helpless. "Come along to your room with me." When inside he pointed to the old red-plush-covered chairs, and said: "Do you recollect my arrival after Straus's visit? I examined those chairs, and saw upon one the traces of chalk. The shoes of the occupant of room No. 11 had been chalked by the boots with his number, and upon the chair I saw traces, and knew that he had stood there to gain the top of your wardrobe." "For what reason?" I asked.