"You--machines--are far more intelligent than we even now, and capable of changing overnight, capable of infinite adaptation to circumstance; you live as readily on Pluto as on Mercury or Earth. Any place is a home-world to you. You can adapt yourselves to any condition. And--most dangerous to them--you can do it instantly. You are their most deadly enemies, and they realize it. They have no intelligent machines; probably they can conceive of none. When you attack them, they merely say 'The life-form of Earth is sending out controlled machines. We will find good machines we can use.' They do not conceive that those machines which they hope to use are attacking them. "Attack--therefore!" "We can readily solve the hidden secret of their force-screen." * * * * He was interrupted. One of the newest science-machines was speaking. "The secret of the force-screen is simple." A small ray-machine, which had landed near, rose into the air at the command of the scientist-machine, X-5638 it was, and trained upon it the deadly induction beam. Already, with his parts, X-5638 had constructed the defensive apparatus, for the ray fell harmless from his screen. "Very good," said Roal softly. "It is done, and therein lies their danger. Already it is done. "Man is a poor thing, unable to change himself in a period of less than thousands of years. Already you have changed yourself. I noticed your weaving tentacles, and your force-beams. You transmuted elements of soil for it?" "Correct," replied X-5638. "But still we are helpless. We have not the power to combat their machines. They use the Ultimate Energy known to exist for six hundred years, and still untapped by us. Our screens cannot be so powerful, our beams so effective. What of that?" asked Roal. "Their generators were automatically destroyed with the capture of the ship," replied X-6349, "as you know. We know nothing of their system." "Then we must find it for ourselves," replied Trest. "The life-beams?" asked Kahsh-256799, one of the Man-rulers. "They affect chemical action, retarding it greatly in exothermic actions, speeding greatly endothermic actions," answered X-6221, the greatest of the chemist-investigators. "The system we do not know. Their minds cannot be read, they cannot be restored to life, so we cannot learn from them." "Man is doomed, if these beams cannot be stopped," said C-R-21, present chief of the machine rulers, in the vibrationally correct, emotionless tones of all the race of machines. "Let us concentrate on the two problems of stopping the beams, and the Ultimate Energy till the reenforcements, still several days away, can arrive." For the investigators had sent back this saddening news. A force of nearly ten thousand great ships was still to come.