"Everything is relative, Mirsky, and you have misused gravely the term 'unlimited.' Our power was, and is, very definitely limited. True, it then seemed ample for our needs, and is far superior to that possessed by the inhabitants of any solar system with which I am familiar; but the beings behind that red screen, whoever they are, have sources of power as far above ours as ours are above those of the Solarians." "How do you know?" "That power, what is it?" "We have, then, the analyses of those fields recorded!" came simultaneous questions and exclamations. "Their source of power is the intra-atomic energy of iron. Complete; not the partial liberation incidental to the nuclear fission of such unstable isotopes as those of thorium, uranium, plutonium, and so on. Therefore much remains to be done before I can proceed with my plan--I must have the most powerful structure in the macrocosmic universe." Roger thought for minutes, nor did any one of his minions break the silence. Gharlane of Eddore did not have to wonder why such incredible advancement could have been made without his knowledge: after the fact, he knew. He had been and was still being hampered by a mind of power; a mind with which, in due time, he would come to grips. "I now know what to do," he went on presently. "In the light of what I have learned, the losses of time, life, and treasure--even the loss of the planetoid--are completely insignificant." "But what can you do about it?" growled the Russian. "Many things. From the charts of the recorders we can compute their fields of force, and from that point it is only a step to their method of liberating the energy. We shall build robots. They shall build other robots, who shall in turn construct another planetoid; one this time that, wielding the theoretical maximum of power, will be suited to my needs." "And where will you build it? We are marked. Invisibility now is useless. Triplanetary will find us, even if we take up an orbit beyond that of Pluto!" "We have already left your Solarian system far behind. We are going to another system; one far enough removed so that the spy-rays of Triplanetary will never find us, and yet one that we can reach in a reasonable length of time with the energies at our command. Some five days will be required for the journey, however, and our quarters are cramped. Therefore make places for yourselves wherever you can, and lessen the tedium of those days by working upon whatever problems are most pressing in your respective researches." The gray monster fell silent, immersed in what thoughts no one knew, and the scientists set out to obey his orders. Baxter, the British chemist, followed Penrose, the lantern-jawed, saturnine American engineer and inventor, as he made his way to the furthermost cubicle of the section. "I say, Penrose, I'd like to ask you a couple of questions, if you don't mind?"