For nearly a century those men lived in space, making swift forays on a planet with a fleet of cargo ships, that revolved about the main ship like satellites when they were not being used. In these trips they would bring back tons of rock, and leave most of it stored in the ships, dumping them into the reservoir of the parent ship when it was needed. Then a swift ship was developed. A ship that could start and stop more quickly than any made before--a ship with acceleration neutralizers. But the machine brains of the Metal Horde never learned the secret. With a small fleet of these, the men drove an attack at the unprotected main brain-machine. There were no men known to live in the system. No other known machine could move without the knowledge of that main machine, but these could. They too had the Dis ray now, and they destroyed the main brain-machine. They were lost in the ensuing fight, but that machine was destroyed. All the remaining machines were equally powerful. Any one of them could have built a brain-machine that could easily conquer the others--but it too would have to bow to its creator. They fought it out. The men had known this would be the result. It was a war such as the system had never before seen. Each force was equal, and could not ally itself with any other, for the machines could not lie or state other than their thoughts, and each wanted supreme power. They developed new weapons, weapons whose strength lay in their number. One by one the machine brains had gone down to defeat, the men of that ship helping to disturb the balance of forces by ever so little, yet always enough to throw one side down to defeat, yet always remaining in hiding. At last there remained but one machine-brain, and its weakened force necessitated its return to the devastated planet. With the destruction of the other brain-machines, the remaining machines that they had previously controlled, automatically obeyed the new master as perfectly as they did the old. They returned to find a new fleet awaiting them. But it was not a vast fleet such as they had encountered before. At once the torpedo-ship machines settled to the ground and began turning out their weapons. But it was all over before they could enter as an important factor. These ships had a new weapon. It was a ball of glowing blue light that was driven along a beam of some vibration, and as it touched any ship, the ship instantly volatized so suddenly as to constitute an explosion. The balls of light lasted about a minute and a half each, but were replaced as quickly as they were used. When they were finally used, they would die down to a dull red glow, then suddenly wink out. They could be swept from one ship to another, taking toll of ten or twelve ships each, and the beam that guided them could drive them with the speed of light and supply an infinite acceleration. They were glowing balls of concentrated energy of some sort, and as such could travel with the speed of light.