"It's the rule," Billy Kasker answered. "The faculty thinks we should see the situation at first hand. Then we will have a better understanding of it." Joe Buckner grunted disdainfully. "You're always sucking in with the big shots and telling everybody what they say." "You asked me. I tried to tell you." Billy Kasker's voice was still pleasant. If a slight glint appeared in his eyes, it remained there for only a second. The museum was an open area many miles long. It was enclosed by a high, electrically charged fence along which guard towers were placed at regular intervals. There was only one gate, to which the instructor led the class. A captain, resplendent in a brilliant uniform, came out of the guard house to greet them. "The graduating class from the Star Institute, eh? Good. We had notice that you were coming. Guard, bring Mr. Phipper a _Thor_ gun, then open the gates." The last was spoken in a brisk tone to the guard who had followed the captain. The _Thor_ gun was brought immediately. It was a small weapon, with a belt and holster. The captain took it from the holster. Watching, Billy Kasker had the impression that the weapon was made of glittering, spun glass. It had a short, heavy barrel in which tiny instruments were visible. Billy Kasker watched very closely. "Do you know how to use it?" the captain asked. "Oh, yes," the instructor answered. "Is it so dangerous in there that we need a _Thor_ gun?" Susan Sidwell said. Susan had majored in ionic chemistry and had graduated with high honors. "No, it isn't dangerous at all," the instructor answered hastily. "The weapon is worn merely for the sake of tradition." "No danger at all, young lady," the captain said. "Nothing to worry about. Not while you've got this, anyhow." He patted the _Thor_ gun which the instructor was buckling to his waist. The gates were open. The instructor in the lead, the group passed through. Billy Kasker brought up the rear. Joe Buckner was directly ahead of him. They went first to see the wreckage of the city--shattered walls, tumbled buildings, streets with rubble still piled in them. Weeds and creeping vines grew over the broken bones of this city as if they were attempting to hide the ugly scars. The instructor adjusted his voice to the proper tone. He had made this same speech to many graduating classes and he knew exactly what he was going to say. "You understand, of course, that this part of the old city was almost completely destroyed in our attack of the year 4021 After Yevbro, or the year 1967, according to the way the natives reckoned time on this planet. This part of it has been allowed to remain the way our ships left it, as an example of the effectiveness of our weapons." His voice gave the impression that he was personally participating in that attack and was enjoying the destruction that had taken place. He stood straight, squared his shoulders and breathed deeply.