"What do you suppose could cause it to come up so fast?"

"I have no idea," Gaby yelled back. "Local heating or cooling, a big change in the air pressure. I don't know what would cause that, though. "

"I think the worst is over. Hey, your teeth are chattering."

"I'm not scared anymore. I'm cold."

Cirocco was feeling it, too. The temperature was plunging. in just a few minutes it had gone from balmy to chilly, and now she judged it was getting down around zero. With the wind coming at sixty klicks, it was no laughing matter. They huddled togeth- er, but she could feel the heat being sucked from her back.

"We've got to get to some kind of shelter," she yelled.

"Yeah, but what?"

Neither of them wanted to move from what little shelter they had. They tried covering each other with dirt and dead leaves, but the wind blew it away.

When they were sure they would freeze to death, the wind stopped. it did not diminish; it stopped dead, and Cirocco's cars popped so hard it hurt. She could not hear until she forced a yawn.

"Wow. I've heard of pressure changes, but nothing like that." - The forest was quiet again. Then Cirocco found that if she listened carefully she could hear the dying ghost of whatever had made the moaning sound. It made her shiver in a way that had nothing to do with the cold. She had never thought of herself as imaginative, but the moan had sounded so human, though on such a mighty scale. It made her want to lie down and die.

"Don't go to sleep, Rocky. We've got something else."

"What now?" She opened her eyes and saw a fine white powder drifting through the air. It sparkled in the pale light.

"I'd call it snow." They went as fast as they could to keep their feet from getting numb, and Cirocco knew it was only the still air that saved them. It was cold; even the ground was cold for a change. Ciroc- co felt drugged. It could not be possible. She was a spaceship captain; how had she ended up trudging through a snowstorm in her bare skin?

But the snow was transitory. At one point it was a few centimeters deep on the ground, but then the heat began to well up from below and it melted quickly. Soon the air was getting warmer. When they felt it was safe, they found a place on the warm ground and went to sleep.

The haunch of meat did not smell too good when they awoke, and neither did Gaby's hide belt. They threw it all away and washed in the stream, then Gaby killed another of the animals they had begun to call smilers. It was as easy as it had been the last time.

They felt much better after breakfast, which they supplemented with some of the less exotic fruits they found in great profusion. Cirocco liked one that looked like a lumpy pear but had meat like a melm. It tasted like sharp cheddar cheese.

She felt as if she could march all day, but it turned out that they could not. The stream, their guide for the whole journey so far, vanished in a large hole at the base of a hill.

The two of them stood on the edge of the hole ;and looked down. It gurgled like the drain of a bathtub, but at long intervals made a sucking sound followed by a deep belch. Cirocco didn't like it, and edged away.

"Maybe I'm crazy," she said, "but I wonder if this is where the thing that ate us gets its water? "

"Could be. I'm not diving in to find out. So what's next?" "I wish I knew."

"We could go back to where we started and wait there." Gaby did not seem enthusiastic about that idea.

"Damn! I thought sure we'd find a place to look around if we went far enough. Do you think the whole inside of Themis is one big rain forest?"

Gaby shrugged. "I don't have enough information, obviously." Cirocco chewed it over for a while. Gaby was apparently willing to let her make the decisions. "Okay. First we go to the top of this hill and see what it's like. One more thing I'd like to try if there's nothing worthwhile up there is to climb one of these trees. Maybe we could get high enough to see something. Do you think we could do it?"

Gaby studied a trunk. "Sure, in this gravity. That's no guarantee we'll be able to stick our heads out, though."

"I know. Let's go up the hill."

It was steeper than the countryside they had come through. There were places where they had to use hands and feet, and Gaby led the way through those because she had more experi- ence in rock climbing. She was agile, much smaller and more limber than Cirocco, and soon Cirocco felt every month of the age difference between them.

"Holy shit, take a look at that!"

"W.hat is it?" Cirocco was a few meters behind. When she looked up she saw only Gaby's legs and buttocks, from a distinctly unusual angle. It was odd, she thought, that she had seen all the male crew members naked, but had to come to Themis to see Gaby. What a strange creature she was with no hair.

"We've found our scenic viewpoint," Gaby said. She turned around and gave Cirocco a hand.

There were trees growing on the brow of the hill, but they did not approach the height of the ones behind them. Though they were dense and overgrown with vines, none was over ten meters tall.

Cirocco had wanted to climb the hill to see what was on the other side. Now she knew. The hill didn't have an other side.

Gaby was standing a few meters from the edge of a cliff. With every step Cirocco took the view adjusted itself, receding, encompassing more area. When she stood beside Gaby she still could not see the cliff face, but she had some idea of how long the drop was. It would he measured in kilometers. She felt her stomach lurch.

They stood at-a natural window formed by a twenty-meter gap between the outermost trees. There was nothing in front of them but air for 200 kilometers.

They were at the edge of the rim, looking across the breadth of Themis to the other side. Over there was a hairline shadow that might have been a cliff like the one they were standing on. Above the line was green land, fading to white, then to gray, and finally becoming a brilliant yellow as her eyes traveled up the sloping side to the translucent area in the roof.

Her eyes were drawn back down the curve to the distant cliff. Below it was more green land, with white clouds hugging the ground or towering up higher than she was. It looked like the view from a mountaintop on Earth, but for one thing. The ground seemed level until she looked to the left or right.

It bent. She gulped, and craned her neck, twisting, trying to make it level, trying to deny that far away the land was higher than she was without ever having risen.

She gasped and clutched at the air, then went down on hands and knees. It felt better that way. She edged closer to the abyss and kept looking to her left. Far away was a land of shadow, tilted on its side for her examination. A dark sea twinkled in the night, a sea that somehow did not leave its shores and come spilling toward her. On the other side of the sea was another area of light, like the one in front of her, dwindling in the distance. Beyond it her view was cut off by the roof overhead, seeming to belly down to meet the land. She knew it was an illusion of the perspective; the roof would be just as high if she stood beneath it at that point.

They were on the edge of one of the areas of permanent day. A hazy terminator began to blanket the land to her right, not sharp and clear like the terminator of a planet seen from space, but fad- ing through a twilight zone she estimated to be thirty or forty kilometers wide. Beyond that zone was night, but not blackness. There was a huge sea in there, twice as large as the one in the

other direction, looking as if bright moonlight was falling on it. it sparkled like a plain of diamond.

"Isn't that the direction the wind came from?" Gaby asked. "Yeah, if we didn't get turned around by a curve in the river." "I don't think we did. That looks like ice to me."

Cirocco agreed. The ice sheet broke up as the sea narrowed to a neck, eventually becoming a river that ran in front of her and emptied into the other sea. The country over there was moun- tainous, rugged as a washboard. She did not understand how the river could thread its way through the mountains to join the sea on the other side. She decided the perspective was fooling her. Water would not flow uphill, even in Themis.

Beyond the ice was another daylight area, this one brighter and yellower than the others she could see, like desert sands. To reach it, she would have to travel across the frozen sea.

"Three days and two nights," Gaby said. "That worked out pretty well from the theory. I said we'd he able to see almost half the inside of Themis from any point. What I didn't figure on were those things."

Cirocco followed Gaby's pointing fimer to a series of what looked like ropes that started on the land below and angled up- ward to the roof. There were three of them in a line almost directly in front of them, so that the nearest partially concealed the other two. Cirocco had seen them earlier, but had skipped over them because she could not understand it all at once. Now she looked closer, and frowned. Like a depressing number of things in Themis, they were huge.

The nearest one could serve as a model for all the rest. It was fifty kilometers away, but she could see that it was made of perhaps one hundred strands wound together. Each strand was 200 or 300 meters thick. Further detail was lost at that distance.

The three in the row all angled steeply over the frozen sea, rising 150 kilometers or more until they joined the roof at a point she knew must be one of the spokes, seen from the inside. It was a conical mouth, like the bell of a trumpet that flared to become the roof and sides of the rim enclosure. At the far edge of the bell, some 500 kilometers away, she could make out more of the ropes.

There were more cables to her left, but these went straight up

to the arched ceiling and disappeared through it. Beyond them were other rows that angled toward the spoke mouth she could not see from her vantage point, the one over the sea in the mountains.

Where the cables joined the ground, they pulled it up into broad-based mountains.

"They look like the cables on a suspension bridge," Cirocco said.

"I agree. And I think that's what it is. There's no need for tow- ers to support it. The cables can be fastened in the center. Themis is.a circular suspension bridge."

Cirocco eased herself closer to the edge. She stuck her head over and looked down two kilometers to the ground.