They waited until the helicopter had climbed to position and was circling above, and then turned their attention to the place where the sheet of fused earth and stone bulged upward. It must have been almost ground-zero of one of the hydrogen-bombs; the wreckage of the Cathedral of Learning had fallen predominantly to the north, and the Carnegie Library was tumbled to the east. "I think the entrance would be on this side, toward the Library," Altamont said. "Let's try it, to begin with." He used the solenoid-hammer, slowly pounding a hole into the glaze, and placed a small charge of the plastic explosive. Chunks of the lavalike stuff pelted down between the little mound and the huge one of the old library, blowing a hole six feet in diameter and two and a half deep, revealing concrete bonded with crushed steel-mill slag. "We missed the door," he said. "That means we'll have to tunnel in through who knows how much concrete. Well--" * * * * * He used a second and larger charge, after digging a hole a foot deep. When he and his helpers came up to look, they found a large mass of concrete blown out, and solid steel behind it. Altamont cut two more holes sidewise, one on either side of the blown-out place, and fired a charge in each of them, bringing down more concrete. He found that he hadn't missed the door, after all. It had merely been concreted over. A few more shots cleared it, and after some work, they got it open. There was a room inside, concrete-floored and entirely empty. With the others crowding behind him, Altamont stood in the doorway and inspected the interior with his flashlight; he heard somebody back of him say something about a most peculiar sort of a dark-lantern. Across the small room, on the opposite wall, was a bronze plaque. It carried quite a lengthy inscription, including the names of all the persons and institutions participating in the microfilm project. The History Department at the Fort would be most interested in that, but the only thing that interested Altamont was the statement that the floor had been laid over the trapdoor leading to the vaults where the microfilms were stored. He went outside to the radio. "Hello, Jim. We're inside, but the films are stored in an underground vault, and we have to tear up a concrete floor," he said. "Go back to the village and gather up all the men you can carry, and tools. Hammers and picks and short steel bars. I don't want to use explosives inside. The interior of the crypt oughtn't to be damaged, and I don't know what a blast in here might do to the film, and I don't want to take chances." "No, of course not. How thick do you think this floor is?" "Haven't the least idea. Plenty thick, I'd say. Those films would have to be well buried, to shield them from radioactivity. We can expect that it'll take some time." "All right. I'll be back as soon as I can."