Somehow he felt no doubt whatever. The five of them walked onto the corroded metal plate together, and the sky faded and ghosts of tube-lights appeared and became brilliant, and they stepped off the plate into a corridor one section removed from the sending-transposer which had translated them all, successively, to wherever they had been. And everything proceeded matter-of-factly. The three men went to the room where metal globes by hundreds waited for the defenders of the fortress to make use of them. They were completely practical, those globes. There were even small footholds sunk into their curving sides so a man could climb to their tops and inspect or change the apparatus within. On the way, Burke explained to Keller. The globes were designed to be targets, and targets they would remain. They'd be set out in the path of the coming Enemy ships, which could not vary their courses. Their circuits would be changed to treat the suddenly increasing gravitational fields as radiation, so that they would first project back a monstrous field of the same energy, and then dive down it to presumed collision with the ships. There was a distinct possibility that if enough globes could be gotten out in space, that at the least they might hit one enemy ship and so wreck the closely orbited grouping. From that reasonable first possibility, the chances grew slimmer, but the results to be hoped for increased. Keller nodded, brightly. He'd used the reading helmets more than anybody else. He understood. Moreover, his mind was trained to work in just this field. When they reached the room of the many spheres he gestured for Burke and Holmes to wait. He climbed the footholds of one globe, deftly removed its top, and looked inside. The conductors were three-inch bars of pure silver. He reached in and did this and that. He climbed down and motioned for Burke and Holmes to look. It took them long seconds to realize what he'd done. But with his knowledge of what could be done, once he was told what was needed, he'd made exactly three new contacts and the globe was transformed to Burke's new specifications. Instead of days required to modify the circuits, the three of them had a hundred of the huge round weapons changed over within an hour. Then Keller went up to the instrument-room and painstakingly studied the launching system. He began the launchings while Holmes and Burke completed the change-over task. They joined him in the instrument-room when the last of the metal spheres rose a foot from the stony floor of the magazine and went lurching unsteadily over to the breech of the launching-tube they hadn't noticed before. "Three hundred," said Keller in a pleased tone, later. "All going out at full acceleration to meet the Enemy. And there are six observer-globes in the lot."