They walked into one such tunnel. The bulk of the Platform above them loomed overhead with a crushing menace. There were trucks rumbling all around underneath, here in this maze of scaffold columns. Some carried ready-loaded cages waiting to be snatched up by hoists. Crane grips came down, and snapped fast on the cages, and lifted them up and up and out of sight. There was a Diesel running somewhere, and a man stood and stared skyward and made motions with his hands, and the Diesel adjusted its running to his signals. Then some empty cages came down and landed in a waiting truck body with loud clanking noises. Somebody cast off the hooks, and the truck grumbled and drove away.
Sally spoke to a preoccupied man in shirt sleeves with a badge on an arm band near his shoulder. He looked carefully at the passes she carried, using a flashlight to make sure. Then he led them to a shaft up which a hoist ran. It was very noisy here. A rivet gun banged away overhead, and the plates of the Platform rang with the sound, and the echoes screeched, and to Joe the bedlam was infinitely good to hear. The man with the arm band shouted into a telephone transmitter, and a hoist cage came down. Joe and Sally stepped on it. Joe took a firm grip on her shoulder, and the hoist shot upward.
The hugeness of the Shed and the Platform grew even more apparent as the hoist accelerated toward the roof. The flooring seemed to expand. Spidery scaffold beams dropped past them. There were things being built over by the sidewall. Joe saw a crawling in-plant tow truck moving past those enigmatic objects. It was a tiny truck, no more than four feet high and with twelve-inch wheels. It dragged behind it flat plates of metal with upturned forward edges. They slid over the floor like sledges. Cryptic loads were carried on those plates, and the tow truck stopped by a mass of steel piping being put together, and began to unload the plates.
Then the hoist slowed abruptly and Sally winced a little. The hoist stopped.
Here--two hundred feet up--a welding crew worked on the skin of the Platform itself. The plating curved in and there was a wide flat space parallel to the ground. There was also a great gaping hole beyond. Though girders rose roofward even yet, this was as high as the plating had gone. That opening--Joe guessed--would ultimately be the door of an air lock, and this flat surface was designed for a tender rocket to anchor to by magnets. When a rocket came up from Earth with supplies or reliefs for the Platform's crew, or with fuel to be stored for an exploring ship's later use, it would anchor here and then inch toward that doorway....