"Of course one can be certain of nothing in this world, dear," was my reply. "But by all the laws of aerodynamics it should, when complete, be able to do what I require. I must be able to carry fuel for twelve hours cruising at low speed, so as to enable me to chase an airship to the coast, if necessary. Further, I must, in order to be successful, be able to climb to ten thousand feet in not more than twenty minutes. You see," I explained, "I am trying to have the engines silenced, and I am fitting up control-gear for two pilots, so as to allow one to relieve the other, and, further, I have designed the alterations whereby either Teddy or myself can have equal facilities to work the searchlight as well as the deadly current." "I do hope it will be a success. You have had so many failures, dear," she said, as we stood together, watching Teddy make a descent, for he was up testing his engine. "Yes, that first magnetic wave idea proved a failure," I said regretfully. "And why, I can't yet discover. My first idea was to create an intensified magnetic wave which would have the effect of `seizing' the working parts of the Zeppelin engines, and putting them out of action. For instance, from your aeroplane you would direct this wave against the Zeppelin and bring its engines gradually into a state of immobility. The natural act of the Zeppelin engineer, on finding that his engine was slowing down, would be to admit more fuel for a few moments. On the sudden release of the arresting medium the engine would `pick-up' violently and blow the heads out of the cylinders, thereby causing the explosion which we desire to create." "Your experiments were all in secret," Roseye remarked. "The theory seems sound enough. Curious that it did not work!" "Yes. Even now I can't, for the life of me, discover the reason," I replied. "Yet we have, happily, tested this new apparatus of ours, and we know it is feasible as soon as ever we can get its weight further reduced, and the ray intensified." "And the sooner you can do that, the better," my well-beloved declared. "Before very long, at the present rate of increase, we shall, I expect, see Zeppelins of a much greater size." "True," I remarked, as I watched Teddy spring out of his bus, and make his way across the aerodrome in our direction. "No time should be lost. To be effective the aeroplane will have to be able to climb to 18,000 feet, and even remain aloft at that height for hours to lie in wait for the airship. The airship of one year hence will inevitably be a much more formidable machine than the present Zeppelin." "But we must be most careful to keep the secret, Claude," she urged. "The enemy must not know it, or they may combat us!" I was silent for a few moments. Across my mind there flashed the recollection of that strange enemy message in cipher that had been found in her card-case.