"I thought of that, and I've been trying to think of other, and if possible, better, cheaper, and quicker ways of getting the necessary power. "Let's eliminate the known sources one by one. The usual ones, the ones men have been using for centuries, go out at once. The atomic hydrogen reaction stores more energy per gram than any other chemical reaction known. Such things as the storage battery, the electro-static condenser, the induction coil, or plain heat storage, are worthless to us. The only other method of storing energy we know of is the method used by the Kaxorians in driving their huge planes. "They use condensed light-energy. This is efficient to the ultimate maximum, something no other method can hope to attain. Yet they need huge reservoirs to store it. The result is still ineffective for our purpose; we want something we can put in a small space; we want to condense the light still further. That will be the ideal form of energy storage, for then we will be able to release it directly as a heat ray, and so use it with utmost efficiency. I think we can absorb the released energy in the usual cavity radiator." A queer little smile appeared on Arcot's face. "Remember--what we want is light in a more condensed form, a form that is naturally stable, and that does not need to be held in a bound state, but actually requires urging to bring about the release of energy. For example--" A shout from Wade interrupted him. "That's really rare! _Whoo_--I have to hand it to you! That takes all the prizes!" He laughed delightedly. In puzzled wonder Morey and the two older men looked at him, and at Arcot who was grinning broadly now. "Well, I suppose it must be funny," Morey began, then hesitated. "Oh--I see--say, that _is_ good!" He turned to his father. "I see now what he's been driving at. It's been right here under our noses all the time. "The light-matter windows we found in the wrecked enemy ships contain enough bound light-energy to run all the planes we could make in the next ten years! We're going to have the enemy supply us with power we can't get in any other way. I can't decide, Arcot, whether you deserve a prize for ingenuity, or whether we should receive booby-prizes for our stupidity." Arcot Senior smiled at first, then looked dubiously at his son. "There's definitely plenty of the right kind of energy stored there--but as you suggested, the energy will need encouragement to break free. Any ideas?" "A couple. I don't know how they'll work, of course; but we can try." Arcot puffed at his pipe, serious now as he thought of the problems ahead. Wade interposed a question. "How do you suppose they condense that light energy in the first place, and, their sun being dead, whence all the light? Back to the atom, I suppose."