tion elsewhere was completed, they had dropped whatever they
were doing, piled into such ships as were completed, and lifted away.

The mushroom-topped tower rose from the middle of a circular building
piled level on level, almost half a mile across. He circled over it,
saw an airship dock, and called the _Harriet Barne_ while Jacquemont
talked to Jerry Rivas, piloting the manipulator-boat. Rivas came in
and joined them in the air; they hovered over the dock and helped the
ship down when she came in, nudging her into place.

By the time Conn and Jacquemont and Rivas and Anse Dawes and Roddell
and Youtsko and Karanja were out on the dock in oxygen helmets, the
ship's airlock was opening and Nichols and Vibart and the others were
coming out, towing a couple of small lifters loaded with equipment.

The airlocked door into the building, at the end of the dock, was
closed; when somebody pulled the handle, it refused to open. That
meant it was powered from the central power plant, wherever that was.
There was a plug socket beside it, with the required voltage marked
over it. They used an extension line from a power unit on one of the
lifters to get it open, and did the same with the inner door; when it
was open, they passed into a dim room that stretched away ahead of
them and on either side.

It looked like a freight-shipping room; there were a few piles of
boxes and cases here and there, and a litter of packing material
everywhere. A long counter-desk, and a bank of robo-clerks behind it.
According to the air-analyzer, the oxygen content inside was safely
high. They all pulled off their fishbowl helmets and slung them.

"Well, we can bunk inside here tonight," somebody said. "It won't be
so crowded here."

"We'll bunk here after we find the power plant and get the ventilator
fans going," Jacquemont said.

Anse Dawes held up the cigarette he had lighted; that was all the
air-analyzer he needed.

"That looks like enough oxygen," he said.

"Yes, it makes its own ventilation; convection," Jacquemont said. "But
you go to sleep in here, and you'll smother in a big puddle of your
own exhaled CO_2. Just watch what the smoke from that cigarette's
doing."

The smoke was hanging motionless a few inches from the hot ash on the
end of the cigarette.

"We'll have to find the power plant, then," Matsui, the power-engineer
said. "Down at the bottom and in the middle, I suppose, and anybody's
guess how deep this place goes."