Lavon had noticed it, just beneath the surface of awareness, but at Shar’s remark he realized that he was gradually being stifled. The oxygen content of the water, luckily, had not dropped, but the temperature suggested the shallows in the last and worst part of autumn. It was like trying to breathe soup.
“Than, give us more action from the Vortae,” Lavon said. “This is going to be unbearable unless we get more circulation.”
There was a reply from Than, but it came to Lavon’s ears only as a mumble. It was all he could do now to keep his attention on the business of steering the ship.
The cut or defile in the scattered razor-edged rocks, was a little closer, but there still seemed to be many miles of rough desert to cross. After a while the ship settled into a steady, painfully slow crawling, with less pitching and jerking than before, but also with less progress. Under it, there was now a sliding, grinding sound, rasping against the hull of the ship itself, as if it were treadmilling over some coarse lubricant the particles of which were each as big as a man’s head.
Finally Shar said, “Lavon, we’ll have to stop again. The sand this far up is dry, and we’re wasting energy using the treads.” •
“Are you sure we can take it?” Lavon asked, gasping for breath. “At least we are moving. If we stop to lower the wheels and change gears again, we’ll boil.”
“We’ll boil if we don’t,” Shar said calmly. “Some of our algae are dead already and the rest are withering. That’s a pretty good sign that we can’t take much more. I don’t think we’ll make it into the shadows, unless we do change over and put on some speed.”
There was a gulping sound from one of the mechanics. “We ought to turn back,” he said raggedly. “We were never meant to be out here in the first place. We were made for the water, not for this hell.”
“We’ll stop,” Lavon said, “but we’re not turning back. That’s final.”
The words made a brave sound, but the man had upset Lavon more than he dared to admit, even to himself. “Shar,” he said, “make it fast, will you?”
The scientist nodded and dived below.
The minutes stretched out. The great red gold globe in the sky blazed and blazed. It had moved down the sky, far down, so that the light was pouring into the ship directly in Lavon’s face, illuminating every floating particle, its rays like long milky streamers. The currents of water passing Lavon’s cheek were almost hot.
How could they dare go directly forward into that inferno? The land directly under the “star” must be even hotter than it was here!
“Lavon! Look at Para!”
Lavon forced himself to turn and look at his proto ally. The great slipper had settled to the deck, where it was lying with only a feeble pulsation of its cilia. Inside, its vacuoles were beginning to swell, to become bloated, pear-shaped bubbles, crowding the granulated protoplasm, pressing upon the dark nuclei.
“Is ... is he dying?”
“This cell is dying,” Para said, as coldly as always. “But go on—go on. There is much to learn, and you may live, even though we do not. Go on.”
“You’re—for us now?” Lavon whispered.
“We have always been for you. Push your folly to the uttermost. We will benefit in the end, and so will Man.”
The whisper died away. Lavon called the creature again, but it did not respond.
There was a wooden clashing from below, and then Shar’s voice came tinnily from one of the megaphones. “Lavon, go ahead! The diatoms are dying, too, and then we’ll be without power. Make it as quickly and directly as you can.”
Grimly, Lavon leaned forward. “The ‘star’ is directly over the land we’re approaching.”
“It is? It may go lower still and the shadows will get longer. That’s our only hope.”
Lavon had not thought of that. He rasped into the banked megaphones. Once more, the ship began to move, a little faster now, but still seemingly at a crawl. The thirty-two wheels rumbled.
It got hotter.
Steadily, with a perceptible motion, the “star” sank in Lavon’s face. Suddenly a new terror struck him. Suppose it should continue to go down until it was gone entirely? Blasting though it was now, it was the only source of heat. Would not space become bitter cold on the instant—and the ship an expanding, bursting block of ice?
The shadows lengthened menacingly, stretching across the desert toward the forward-rolling vessel. There was no talking in the cabin, just the sound of ragged breathing and the creaking of the machinery.
Then the jagged horizon seemed to rush upon them. Stony teeth cut into the lower rim of the ball of fire, devoured it swiftly. It was gone.
They were in the lee of the cliffs.
Lavon ordered the ship turned to parallel the rock-line; it responded heavily, sluggishly. Far above, the sky deepened steadily, from blue to indigo.
Shar came silently up through the trap and stood beside Lavon, studying that deepening color and the lengthening of the shadows down the beach toward their world. He said nothing, but Lavon was sure that the same chilling thought was in his mind.
“Lavon.”
Lavon jumped. Shar’s voice had iron in it. “Yes?”
“We’ll have to keep moving. We must make the next world, wherever it is, very shortly.”
“How can we dare move when we can’t see where we’re going? Why not sleep it over—if the cold will let us?”
“It will let us,” Shar said. “It can’t get dangerously cold up here. If it did, the sky—or what we used to think of as the sky—would have frozen over every night, even in summer. But what I’m thinking about is the water. The plants will go to sleep now. In our world that wouldn’t matter; the supply of oxygen there is enough to last through the night. But in this confined space, with so many creatures in it and no supply of fresh water, we will probably smother.”
Shar seemed hardly to be involved at all, but spoke rather with the voice of implacable physical laws.
“Furthermore,” he said, staring unseeingly out at the raw landscape, “the diatoms are plants, too. In other words, we must stay on the move for as long as we have oxygen and power—and pray that we make it.”
“Shar, we had quite a few protos on board this ship once. And Para there isn’t quite dead yet. If he were, the cabin would be intolerable. The ship is nearly sterile of bacteria, because all the protos have been eating them as a matter of course and there’s no outside supply of them, any more than there is for oxygen. But still and all there would have been some decay.”
Shar bent and tested the pellicle of the motionless Para with a probing finger. “You’re right, he’s still alive. What does that prove?”
“The Vortae are also alive; I can feel the water circulating. Which proves that it wasn’t the heat that hurt Para. It was the light. Remember how badly my skin was affected after I climbed beyond the sky? Undiluted starlight is deadly. We should add that to the information from the plates.”
“I still don’t get the point.”
“It’s this. We’ve got three or four Noc down below. They were shielded from the light, and so must be alive. If we concentrate them in the diatom galleys, the dumb diatoms will think it’s still daylight and will go on working. Or we can concentrate them up along the spine of the ship, and keep the algae putting out oxygen. So the question is: which do we need more, oxygen or power? Or can we split the difference?”
Shar actually grinned. “A brilliant piece of thinking. We may make a Shar of you yet, Lavon. No, I’d say that we can’t split the difference. There’s something about daylight, some quality, that the light Noc emits doesn’t have. You and I can’t detect it, but the green plants can, and without it they don’t make oxygen. So we’ll have to settle for the diatoms—for power.”