"I was almost certain that it wouldn't explode," the stranger said, chattily. "You see, I haven't derived that formula yet, so I couldn't make a real explosive. I could of course, materialize beside you, under your protective screen, and crush you in a vise. I could materialize as a man of metal, able to stand up under this acceleration, and do you to death. I could even, by a sufficient expenditure of mental energy, materialize a planet around your ship and crush it. However, these crude methods are distasteful in the extreme, especially since you have already given me some slight and unexpected mental exercise. In return, I shall give you one chance for your lives. I cannot dematerialize either you or your vessel until I work out the formula for your peculiar atomic structure. If I can derive the formula before you reach the boundaries of my home-space, beyond which I cannot go, I shall let you go free. Deriving the formula will be a neat little problem. It should be fairly easy, as it involves only a simple integration in ninety-seven dimensions." * * * * * Silence ensued, and Seaton advanced his lever to the limit of his ability to retain consciousness. Almost overcome by the horror of their position, in an agony of suspense, expecting every instant to be hurled into nothingness, he battled on, with no thought of yielding, even in the face of those overwhelming mental odds. "You can't do it, old top," he thought savagely, concentrating all the power of his highly-trained mind against the intellectual monster. "You can't dematerialize us, and you can't integrate above ninety-five dimensions to save your neck. You can't do it--you're slipping--you're all balled up right now!" For more than an hour the silent battle raged, during which time the Skylark flew millions upon millions of miles toward Earth. Finally the stranger spoke again.