Tommy shook his head impatiently, staring at the so-simple, yet incredible device whose theory had been mathematically proven numberless times, but never put into practice before. "Having made this device," said Von Holtz, "the Herr Professor constructed what he termed a catapult. It was a coil of wire, like the large machine there. It jerked a steel ball first vertically, then horizontally, then laterally, then in a fourth-dimensional direction, and finally projected it violently off in a fifth-dimensional path. He made small hollow steel balls and sent a butterfly, a small sparrow, and finally a cat into that other world. The steel balls opened of themselves and freed those creatures. They seemed to suffer no distress. Therefore he concluded that it would be safe for him to go, himself. His daughter refused to permit him to go alone, and he was so sure of his safety that he allowed her to enter the globe with him. She did. I worked the catapult which flung the globe in the fifth dimension, and his device for returning failed to operate. Hence he is marooned." "But the big catapult--" "Can you not see that the big catapult is broken?" demanded Von Holtz bitterly. "A special metal is required for the missing parts. That, I know how to make. Yes. I can supply that. But I cannot shape it! I cannot design the gears which will move it as it should be moved! I cannot make another dimensoscope. I cannot, Herr Reames, calculate any method of causing four right angles to be all at right angles to each other. It is my impossibility! It is for that that I have appealed to you. You see it has been done. I see that it is done. I can make the metal which alone can be moved in the necessary direction. But I cannot calculate any method of moving it in that direction! If you can do so, Herr Reames, we can perhaps save the Herr Professor Denham. If you cannot--Gott! The death he will die is horrible to think of!" "And his daughter," said Tommy grimly. "His daughter, also." * * * * * He paced up and down the laboratory again. Von Holtz moved to the work-bench from which he had taken Denham's note. There was a pile of such memoranda, thumbed over and over. And there were papers in the angular, precise handwriting which was Von Holtz's own, and calculations and speculations and the remains of frantic efforts to work out, somehow, the secret which as one manifestation had placed one mirror so that it hurt the eyes to look at it, and one other mirror so that from every angle of a normal existence, one could see only the edge. "I have worked, Herr Reames," said Von Holtz drearily. "Gott! How I have worked! But the Herr Professor kept some things secret, and that so-essential thing is one of them." Presently he said tiredly: