He went to another vision-screen with an image of another part of the outer surface. He turned that knob, and the image dissolved into another. This was a gigantic room, lighted like more familiar places. In its center there was an enormous, gigantic machine. There were domes of metal, with great rods of silvery stuff reaching across emptiness between them. There were stairs by which one could climb to this part and that. Judging by the steps and the size of the light-tubes, the machine was the size of a four-storey house. And on the floor there were smaller machines, all motionless and all cryptic.
Keller said with conviction, "Power!"
Burke stared. Keller recovered the original view and went to still other plates. In succession, as he turned the knobs, Burke saw compartment after compartment. There was one quite as huge as the one containing the power-generating machine. It contained hemispheres bolted ten feet above the floor on many columns. There was a network of bus-bars, it seemed, overlying everything, and there were smaller devices on the floor below it.
"Gravity!" said Keller with conviction.
"Good enough," said Burke. "We've found something too, which may be useful with those machines. If we can—"
Keller held up his hand and went to one special screen. When he changed the image, the new one was totally unlike any of the others. This was a close-up. It showed a clumsy, strictly improvised and definitely cobbled metal case against a wall. It had been made by inept hands. It was remarkable to see such indifferent workmanship here. But the really remarkable thing was that the face of the box contained an inscription, burned into the metal as if by a torch. The symbols had no meaning to Burke, of course. But this was an inscription in a written language.
Keller rubbed his hands, beaming.
"It could be a message for somebody who'd come later," said Burke. "It's hard to think of it being anything else. But it wasn't placed for us to find. It should have been set up beside the ship-lock we were expected to come in by and did come in by."
"We'll see," said Keller zestfully. "Come on!"
Burke followed him. Keller seemed somehow to know the way. They went all the way back to the ship-lock, passed it, and then Keller dived off to the right, down an unsuspected ramp. There were galleries running in every direction here, crossing each other and opening upon an indefinite number of what must have been storerooms. Presently Keller pointed.