To the uninitiated the long shed with its two lathes, its tangle of electric wires across the floor, the great induction coils--some of them capable of giving a fourteen-inch spark--the small dynamo with its petrol engine, and other electrical appliances, would no doubt have been puzzling. Upon the benches stood some strange-looking wireless condensers, radiometers, detectors and other objects which we had constructed. Also dressed in overalls, as was my chum and fellow-experimenter, I was engaged in assisting him to adjust a small vacuum tube within that heavy, mysterious-looking wooden box which I daily carried aloft with me in the fuselage of my aeroplane. We smoked "gaspers" and chatted merrily, as we worked on, until at last we had completed the job. "Now let's put a test on it again--eh, Claude?" my friend suggested. "Right ho!" I acquiesced. It was already dusk, for the repair had taken us nearly four hours, and during the past half-hour we had worked beneath the electric light. The shed was on one side of the large market-garden, at a considerable distance from any house. Indeed, as one stood at the door there spread northward several flat market-gardens and orchards, almost as far as the eye could reach. Presently, when we had adjusted the many heavily-insulated wires, I started the dynamo, and on turning on the current a bright blue blinding flash shot, with a sharp fierce crackling, across the place. "Gad! that's bad!" gasped Teddy, pale in alarm. "Something's wrong!" "Yes, and confoundedly dangerous to ourselves and to the petrol--eh?" I cried, shutting off the dynamo instantly. "Phew! It was a real narrow shave!" remarked Teddy. "One of the narrowest we've ever had!" "Yes, my dear fellow, but it tells us something," I said. "We've made an accidental discovery--that spark shows that we can increase our power a thousandfold, when we like." "It has, no doubt, given the wireless operators at the Admiralty, at Marconi House, and elsewhere a very nasty jar," laughed Teddy. "They'll wonder what's up, won't they?" "Well, we can't help their troubles." I laughed. "I expect we've jammed them badly," Teddy said. "Look the aerial is connected up!" "By Jove! so it is?" I said. I saw what I had not noticed before, that the network of phosphor-bronze aerial wires strung beneath the roof of the shed had remained connected up with the coils from an experiment we had conducted on the previous afternoon. "I'll pump Treeton about it to-morrow. He'll be certain to have heard if there has been any unusual signals at Marconi House," I said. "They'll no doubt believe that spark to be signals from some new Zeppelin!" "No doubt. But we may thank our stars that we're safe. Both of us could very easily have been either struck down, or blown up by the petrol-tank. We'll have to exercise far more caution in the future," declared Teddy.