Mars Center failed in fact the next time Phobos rode high over it. The apparatus here had been carefully destroyed by technicians with a view of making it indecipherable, but the Mirans made it even more certain, for no ship settled here to investigate, but a stream of atomic bombs that lasted for over an hour, and churned the rock to dust, and the dust to molten lava, in which pools of fused tungsten-beryllium alloy bubbled slowly and sank. "Ah, Jarth--they are a brave race, whatever we may say of their queer shape," sighed Gresth Gkae as the last of Mars Center sank in bubbling lava. "They stung as they died." For some minutes he was silent. "We must move on," he said at length. "I have been thinking, and it seems best that a few ships land here, and establish a fort, while some twenty move on to the satellite of the third planet and destroy the fort there. We cannot operate against the planet while that hangs above us." Seven ships settled to Mars, while the fleet came up from Jupiter to join with Gresth Gkae's flight of ships on its way to Luna. An automatically controlled ship was sent ahead, and began the bombardment. It approached slowly, and was not destroyed by the UV beams till it had come to within 40,000 miles of the fort. At 60,000 Gresth Gkae stationed his fleet--and returned to 150,000 immediately as the titanic UV beams of the Lunar Fort stretched out to their maximum range. The focus made a difference. One ship started limping back to Jupiter, in tow of a second, while the rest began the slow, methodical work of wearing down the defenses of the Lunar Fort. Kendall looked out at the magnificent display of clashing, warring energies, the great, whirling spheres and discs of opalescent flame, and turned away sadly. "The men at Deenmor must have watched that for days. And at Mars Center." "How long can we hold out?" asked McLaurin. "Three weeks or so, at the present rate. That's a long time, really. And we can escape if we want to. The UV beams here have a greater range than any weapon the Strangers have, and with Earth so near--oh, we could escape. Little good." "What are you going to do?" "I," said Buck Kendall, suddenly savage, "am going to consign all the math machines in the universe to eternal damnation--and go ahead and build a machine anyway. I _know_ that thing ought to be right. The math's wrong." "There is no other thing to try?" "A billion others. I don't know how many others. We ought to get atomic energy somehow. But that thing infuriates me. A hundred things that math has predicted, that I have checked by experiment, simple little things. But--when I carry it through to the point where I can get something useful--it wriggles off into--uncertainty."