Bill was on his feet with that mulish look he has when he's sure he's right. "It's impossible!" he snapped. "No metal can reflect all wavelengths. No substance can resist a force greater than those which created it and hold it together. As for magnetism, gravitation, they're space-warp forces. _Things_ can't stop them. Sorry we're not in the market for Sunday features today, and I rather doubt that Herr Nebel is. You've got brains--I'll grant you that. You have some energy source in the handle of that little gun of yours that would turn industry up on its tail overnight. I haven't the slightest doubt in the world that you may have blasted the atom wide open and made it sit up and beg. But there's no substance, known or unknown, that will do what you claim, and there never will be. If you have no objections, Monsieur, we will be on our way, and in exactly one hour I will call the police. Au revoir, Monsieur." Dampier was hopping from one foot to the other like a hen on ice. "No, no, no, Monsieur!" he cried. "You have not heard all! You must lend another ear! There is no substance that will reflect all things; that is true. Only a fool would believe it. But what of a wall that has no substance--that has no existence in what we call reality but that is as fixed and unshakable as the roots of the universe--a wall, a discontinuity _of Space itself_?" Bill stopped halfway up the stairs. "Say that again," he demanded. The little Frenchman's hands went winging out in hopeless resignation. "There are no words! One does not explain the theories of Dirac and Schroedinger in words. There are symbols--the logic of symbols--that can be translated at last into reality that men can see, but there are no words for the things that are born and live only here, in the head, in the think-box. It is here, in these symbols, on these sheets of paper. It is there, in that apparatus which you see. But it is not in words." Bill wasn't being stopped now. He lives words. "You mean," he said, "that you've hit on a condition of Space--maybe a discontinuity of some kind--that has the property of absolute total reflection? It will reflect all radiations one hundred per cent. Any material body will bounce off without making the slightest impression. Every force exerted on it is turned back on itself--even space-forces like gravitation and magnetism. And you can create that condition at will. Is that what you mean?" Dampier's black eyes fairly spit sparks. "That is it, Monsieur," he cried. "You have said it with a full mouth! My wall, my zone as I have called it, will reflect completely all things, although it is itself a nothing, without existence in our universe. It lives in the symbols of mathematics, and I have just this day completed the apparatus which will give these symbols reality--which will create the zone as I desire it, in any shape or size. I will show you, and you will believe. And then we shall see about Herr Wilhelm Nebel and his makers of wars!"