He had returned to the subject by which he seemed obsessed. Yet, after all, this was not surprising, for many people talked air-raids incessantly. One section of the public, as usual, blamed the authorities, while the other supported them. "Well," I said cheerily, "there's a new invention they are all talking of at Hendon to-day. Somebody has claimed to be able to construct a biplane which will rise from the ground without running, and can attain any speed from ten to two hundred miles an hour." "Phew! That's interesting," exclaimed Lionel, raising himself upon his elbow, and taking a sip of a glass of barley-water at his side. "And who is this wonderful man who has such a wonderful scheme?" "Oh, I forget his name," I said. "But the theory, as far as I can gather, is rather a good one. He can rise so quickly." "How?" "Well," I replied. "From what I can hear, there is a kind of rotary wing--not a propeller and not a thing which can be classed as a helicoptic." Lionel Eastwell grew intensely interested in the new invention which everybody at the aerodrome was discussing. "Yes," he said. "I follow. Go on, Claude. Tell me all you've heard about it. The whole thing sounds most weird and wonderful." "Well," I said, "from what I can find out, the machine is not designed to screw itself through the air in the direction of its axis, or, by pushing the air downwards, to impart upward motion to the structure, as a screw propeller in water imparts a forward motion to the vessel by pushing the water backwards. The biplane is designed to obtain by a rotary motion the same upward thrust in opposition to the downward pull of gravity as the flapping wings, and the passive outspread wings of birds, and to obtain it by the blades being projected through the air in such a manner as to extract and utilise the practically constant energy of the expansive force of the air." "By Jove!" my friend exclaimed, stirring himself in his bed. "That theory is very sound indeed--the soundest I've ever heard. Who's invented it?" "As I've told you, I've forgotten," I replied. "But what does it matter? There are hosts of new inventions every month, and the poor misguided public who put their money into them generally lose it. But I quite agree that the general idea of this is splendid. The war-inventions authorities ought at once to take it up hot and strong. The inventor is, no doubt, an ingenious man of thought and knowledge-- whoever he may be. But alas! nobody ever meets with very much encouragement in aeronautics." "No," he said, pillowing his head comfortably. "It is all so mysterious. We take on a wild-cat idea one day and manufacture machines that are declared to work miracles. Then, next week, we abandon the type altogether, and woo some other smooth-tongued inventor." "That's just it," I laughed. "If the authorities could only adopt some really reliable type to fight Zeppelins. But alas! it seems that they can't," I added.