Part 6

His rabbit had a nice litter at last, and Robin carefully saw that they were kept well supplied with food and drink. He would eat no more meat until there were several dozen adults, all breeding. But he felt that now he was assured of a source of clothing when his own would give out. He knew that eventually he would have to dress himself entirely in the products of his own ingenuity. His Earth clothes could last no more than a few years. He had already devised for himself an experimental pair of sandals from the rinds of the ball-tree fruit and the stalks of the Moontrees. They would do, and he carefully removed his shoes and put them away. When he had heavy exploring to do, or if and when he might try to reach the surface, he would need his good heavy leather shoes. Until then, the makeshift sandals would do.

For he knew that someday he would have to reach the surface. If and when the first astronauts arrived, they would not go below. They would probably never suspect the presence of these unseen areas beneath the crust, possibly not for many dozens of years. It would be on the surface that Robin would have to go to find rescue. That was the greatest problem he would have to solve. Against that terrible trip, he would have to conserve and plan.

Meanwhile, he had a toehold on life here, if conditions within his sublunar cavern did not change. But they were changing ... and not for the better.

_9. From Stone Age to Iron Age_

When he woke up one morning Robin was vaguely aware of something different. He opened his eyes to the dark interior of his cave-home and lay there on his bed of padding from the cargo chamber. For a while he rested quietly in that pleasant half-sleep of awakening after a good rest. Unconsciously his hand moved down searching for a blanket, but of course there was none. He'd never needed one before.

He unconsciously groped again for the blanket, then opened his eyes wide and sat up. There was a slight chill in the air at that! Now he noticed the monkey, asleep, curled up tightly against his leg. That was odd because previously the little fellow had slept outside. What had brought him in?

Robin got up and Cheeky, as Robin had named his friend, woke up instantly and leaped to his shoulder. "What's the trouble, fellow?" asked Robin, patting him on the head. Then the young man left the cave and looked around. At first nothing seemed greatly changed. The temperature had dropped a few degrees, no doubt about it. Yet there was no special draft, no break in the bubble walls to account for it.

He looked at the plants and then realized that some of them were beginning to change color. A grayness was creeping in subtly. The balls of Moontree fruit, which had been his chief sustenance, were showing signs of wrinkling and had either already shriveled or were beginning to.

Robin glanced around sharply, looked into his notebook calendar. He calculated the days that had passed. When his rocket had crashed the Moon had been full. This meant it was high noon of a Lunar day on the surface above. But a Lunar day lasted about a Terrestrial month--twenty-eight days to be exact. When the sun was at its height, the temperature of the surface crust was to be measured as high as 240 degrees Fahrenheit. By sunset it might be down to 160 degrees, but immediately after sunset it would drop with great speed and shortly begin to go as low as a hundred below zero and continue to drop for yet another hundred degrees.

And Robin had perhaps been in his sublunar cavern for ten or maybe twelve days. The sun had set above, the Lunar night was there. Though the cavern was insulated by the best sort of insulation in the universe--a honeycomb of several miles between the surface and itself--a honeycomb in many cases consisting of sealed bubbles, some near vacuums--there was bound to be a gradual loss of the stored-up heat from the long Lunar day. It might take a while for this to become noticeable, especially in view of the obviously warm volcanic action from the unseen areas near the core of the Moon below, yet there it was.

So now Robin knew that the Lunar day did have a counterpart here, that there would be monthly seasons in his cavern and that he was facing a winter that might last ten days more.

He looked around, pondering this. Could he survive? He had probably only a short time to work this out. Obviously he had to work fast and make good.

"Come, Cheeky," he said, "no time for foolishness. No daily swim in the river this morning. Harvest time is here."

He glanced at his rabbits, but they did not seem to mind the temperature drop. He went into the clumps of Moontrees and began to gather their fruit--the big balls--as fast as possible. They were still plump enough to hold food-pulp. He realized that if he waited, they would probably dry up on their trees, shrivel to seed as the increasing cold drew the moisture from them. He spent that day in gathering a harvest, in piling great masses of the fruit in a small cavern-wall bubble near his sleeping chamber. When he had amassed enough to see him through at least two weeks, he gathered the fallen trunks and dried-up old stalks and piled them in the narrow entrance to this storage cave. He built a fire there, paced it out, and spread it out to burn slowly. He would have to keep this fire going and another like it in front of his own sleeping cavern.

He transferred the rabbits to his bubble-home also, rebuilding their pen.

As he had expected, the temperature in his hidden world continued its fall. A few days later it was quite chilly and the Moontrees had acted as he surmised. Their fruits had withered quite rapidly, finally dropping off as small hard seeds. The tree stalks dried out, turned hard, and fell. Robin gathered them as fuel for his fires, found that they were quite excellent, and also that the fresh-fallen ones could be woven into basketry.

The river continued to flow, but was more sluggish, and its waters began to grow cold. On the other hand, the Moonworms and other little creatures seemed to be having their heyday. They were out in quantities greater than he had ever seen and were busily gathering the fallen seeds, carrying them away, evidently preferring them to the fruit.

Robin made himself a jacket from an extra part of the padding, stitching it together with cord and thongs made from shell fibers. With a fire going at the door of his cave, he found he still wouldn't need blankets.

During the balance of the Lunar night Robin was forced to remain close to his caves, tending his fires, conserving all his energies. Outside, the temperature never actually reached freezing, or at least not that Robin could estimate. But at its worst, it was definitely chilly and the river fairly cold.

The view within the cavern cleared somewhat of its usual mugginess and he could see much more. He could now make out the walls on all sides, and discovered that the farthest distance, in the direction in which the river ran, was perhaps several miles off. The vegetation had mainly flattened, was drying up, and he could see everywhere the little ball-segmented insects humping and squirming about.

He saw a number of varieties he had not noticed before. One day venturing out with his bow and arrow, he disturbed something working amid a pile of broken stalks. The thing rushed out, directly at him. It was large, as large as a dog, and it ran straight for him silently, its wide mouth gaping.

He shot it, saw it fall over as it was about to leap at him. When he dug his arrow out, he saw that it was no wormlike insect, no segmented creature. It was a recognizable animal, a creature with two short stubby feet, two small extensions that were like hands on each side of an oval body. A definite head surmounted this, with one eerie eye set in the middle over its wide mouth. Two little breathing holes in the side attested to its possession of lungs. A long, curving rod grew out of the top of its skull and held a large yellow light-ball over it.

There was yet another peculiarity about this Moonhound, as Robin called it. It had no definite color. Its skin was faintly transparent, and he could see its inner organs shadowy within.

All this reminded Robin that there must be vast cavern worlds totally without light, yet having flora and fauna.

When there is no light, there is no need for pigmentation. Hence, this creature had none.

Robin also surmised that it was probably the cold that drove this beast into the lighted cavern in search of food, for he had never seen evidence of anything that large during the warm period.

Robin brought the carcass back to his cave and went to work to skin and cook it. At first he was not going to, for the hairless, colorless nature of it was rather repellent. But one thing Robin had learned long ago was not to let his emotions dictate to his needs. Like it or not, he was going to make use of everything here he could. He had a task, and that was to survive.

As a matter of fact, the meat cooked very nicely, turned brown in the fire, and tasted good. Further, it had a bone structure, which the Moonworms hadn't, and Robin saved these bones, knowing that there were many things that they could be used for. He remembered museum exhibits of bone needles, bone knives, and bone implements, including arrowheads and buttons that the Indians had made use of.

After that, Robin deliberately hunted for these Moonhounds and caught several others before the winter was over.

The warmth returned about when Robin had figured, starting a day or so after the surface sunrise. It rose rapidly, faster than it had fallen, and just as fast, new Moontrees were shooting up, new Moonmushrooms were growing, and the river was becoming warmer.

As time went on and month followed month, Robin found himself working into a comfortable, if primitive, routine. He charted exactly what to do on what days. He could tell in advance what he would be eating, what he would be harvesting. His rabbits had become sufficient in number to permit slaughtering, and he began to acquire a pile of rabbit furs. He found it no longer possible to keep all his rabbits in one pen, and finally liberated the majority of them and left them to shift for themselves. This worked out fine, and he never lacked the sight of at least one or two bunnies anywhere he looked. During the two weeks of winter each month they simply holed up as they might have done on Earth. It was an odd sight seeing the rabbits run wild, for their powerful leg muscles were many times stronger than was required by the weak gravity and, when they ran in a hurry, they would bounce many feet high in fantastic leaps.

Robin was now wearing a rabbit-fur outfit of coat, pants, and hat during the winter periods, equipped with bone buttons he'd carved from the Moonhound skeletons. He was, if anything, beginning to gain weight, but he was also aware of the paleness of his skin. He wondered whether staying in this sunless world a sufficient number of years would not make him as palely transparent as the Moonhounds.

But all this time Robin had not forgotten his ultimate mission--to reach the surface and signal for help. He had worked out the problem in his own mind. He had to make some sort of space suit, something that would permit him to venture out on the nearly airless surface long enough to set up a signal that astronomers might see.

He knew he had the materials for part of this suit in the metal salvaged from the rocket nose. He could polish a section sufficiently to make a heliograph with which he could flash a code message to any high-powered telescope that might be pointed his way. But he had also to fashion the metal into an airtight space helmet, and that he did not know how to do. The suit itself he could probably fashion from cloth and tanned skins, sew and seal it tight enough with animal fats and bone glue to be airtight for a short period, but he needed the helmet. He had the glass for it too, the little peepholes for the camera outlets and a large circular plate that had been set in the very base of the cargo nose and evidently intended for a wide-vision camera shot of the Earth. This plate would be his face plate.

Robin was aware of the hissing noise that he had first noticed on his arrival, but he had never investigated it. It was far off, somewhere along the wall of the cavern. One work period, when he found himself ahead of schedule, he set out to find the source of the noise.

Following the wall, with Cheeky running ahead chattering, the hiss gradually grew in volume. Robin made his way over a sharp cleft, skirted a large bubble-cave in the wall, and after about two miles of walking, came upon the source.

Issuing from a break in the outer cavern wall was a stream of blue flame. For several hundred feet around it no vegetation grew, the ground being covered with thin gray ash. Robin looked at the loudly hissing lance of blue fire.

It probably was a breakthrough from some adjoining bubble, one filled with a gas of some inflammable sort. Somehow in the course of the breakthrough, this leakage had been set aflame. And there it was now, a burning gas jet, sharp and hot.

At that moment, Robin knew he had the answer to his metalworking problem. He'd tried to melt the metal of the rocket over his fires but he had been totally unsuccessful. But this jet, this hot blue flame, this surely would do the trick!

For him the space helmet was now a certainty. It might take time, but now it could be done. That and more was possible, for he had enough metal to make a few necessities like a decent frying pan and a pot to use for boiling and perhaps a water container for a really long exploration trip.

That was the end of Robin's first "Stone Age" period and the beginning of his "Iron Age."

_10. The Incredible Footprints_

Using the gas jet proved to be considerably more difficult than might have been supposed. It was hard to approach too closely to the thing without running the danger of getting scorched. Also, to hold metal in it long enough to allow it to melt or become pliable it was necessary to find a way of holding the object without getting burned.

Robin did get several blisters before he finally worked out a system. Making himself a pair of thick rabbit-skin gloves lined with a thin coating of the ash from the area around the flame proved to be part of the solution. A pair of bone pliers proved to be another part, though the necessity of replacing these was continuous.

Working patiently then, Robin managed to cut and work some of the sheets of metal from the rocket nose. He made himself a hammer of hard stone with which to pound some shape into his pieces and finally had fashioned for himself a serviceable, though crude, frying pan and other implements he needed.

His next project was to be the space helmet, the first essential part of any space suit. He considered this a long time, planning just how to make it. He had a good sheet of metal for the job, but he didn't want to make any errors in working it, and he wanted to have as few seams as possible. Welding had thus far proved a task he had not mastered. He considered making the joints airtight by means of some sort of vegetable- or animal-fat product.

Robin sat in his cave watching the rebirth of life in the bubble-world after one of the winter half-months and thinking. He watched his monkey, Cheeky, turning over rocks for Moonworms--although the little brown pet had never been able to eat them, he seemed to enjoy the hunting of these odd creatures. He watched the rabbits bounding around, listened to those he kept penned up in the next cave.

"What am I waiting for?" he asked himself, half aloud. The monkey stopped at the sound of his voice, looked at him. Robin had developed the habit of talking to himself. He was aware of the danger that years of this hermit's life might well cause him to forget how to talk, and he did not want that. "I can't use a space suit until I can find a way to the surface--a safe way. And I've never even really explored this cavern itself. Maybe there's a simpler way of communication with the surface."

He sat and thought. The monkey dashed over to him, jumped on his knee, chattering. "I really ought to get about exploring this place," Robin went on. "You know, Cheeky, there might be some more things we can use. What do you say, shall we spend this next week playing Columbus, looking for more bubble worlds to conquer?"

The monkey chattered happily, jumped off his knee, and ran around. "Guess you like the idea," said Robin. "Let's get about it, then."

He got up and made his preparations. He filled a sack with enough food for several days. He took his homemade canteen, made from a hollowed-out Moontree fruit rind, filled it with water and hung it around his neck. He took his flashlight and knife, his bow and arrow, and his lantern of light organs. He had discovered that the little light-giving bulbs the animals carried would glow for about two days after their removal, and therefore he constantly kept this lantern refilled with his latest catches.

He looked to see whether his special lot of penned rabbits had enough food and water for the period and then, whistling to Cheeky, Robin set out. He went down to the bank of the flowing stream on which he had been originally carried and then set out to follow this rivulet its length into the distances of the bubble-world.

He followed the flowing stream for about twelve miles. The bubble widened out and the water, which had originally brushed the other side of the cavern where Robin had lived, had now narrowed as a bank of dry ground formed on the opposite side. Robin found himself walking through an ever deepening thicket of growing Moontrees which went on for many miles.

The stream twisted and moved off at right angles finally rushing into a deep pool. Robin went over and gazed into it. Plainly the pool had some sort of underground opening, for the water was swirling around with no visible surface outlet. So this was where the stream ran to! Doubtless it emptied into another bubble somewhere below, probably to fall like a waterfall into that space, there to become another stream and empty still again farther down until it ended in some vast reservoir of sublunar seas.

But Robin was not interested in going farther down, he sought a way upward toward the surface, toward the sight of Earth. He turned away from the whirlpool, walked boundingly on to the farther wall of his home-bubble.

He reached it in time for his sleep period. It seemed as solid and impregnable as the wall around his home region.

Robin and Cheeky slept next to the wall and after their sleep resumed their search. Robin walked along the wall, looking again for some break. He saw in the distance a jagged line of black against the shining brown-gray of the cliff. When he reached it, it was a crack, a break in the surface of the bubble, reaching up several hundred feet. He came up to it.

It was wide, about ten feet wide, and dark. Robin shone his flashlight in, but as far as its rays could reach it was a dark tunnel. "Maybe this is what we're looking for," Robin said to Cheeky. "It seems to slant slightly upward. Maybe it will take us to the next bubble."

Cheeky peered in, walked in slowly and out of sight. "Hey," called Robin, "wait for me!" He followed the scampering monkey.

Now his lantern proved handy. The glow it shed could barely be noticed in the light of the great bubble, but here in the darkness of the cleft, the pale glow was distinct and definitely illuminated the ground a few feet in front of him. On he walked, holding the lantern ahead of him, watching Cheeky's long tail flick in and out of its circle of dim light, as the monkey would dash ahead and dash back.

Soon Robin found himself walking in almost total darkness, save for the limited glow of his lantern. The floor of the cleft occasionally slanted sharply, sometimes breaking steeply downward, sometimes necessitating jumps upward into the darkness. In the Moon's light gravity, Robin was a fantastic jumper, but the darkness made the problem very disconcerting. It was a strange thing to have to leap upward into a black void in hopes that what seemed like a wall in front of you would turn out to have a top and be but a giant step upward. He soared in the darkness, not knowing how near or how far the roof of the tunnel was, feeling strangely disembodied, the monkey clinging to his neck in transit.

He missed several such jumps, managed to avoid being bruised severely only by the feathery softness with which he fell afterward. When the going was straight, Cheeky would leap down and go ahead.

Suddenly he heard a screeching from the monkey. He stopped, flashed his flashlight. The monkey was clutching the edge of a deep break, a pit cut sharply across the floor of the tunnel. Robin quickly reached the spot, scooped up Cheeky. His flashlight revealed the other side of the pit several yards away. Turning its rays downward, he could see no bottom to this crack within the tunnel. He shuddered, thinking what might have happened had he gone into it. Then, gathering Cheeky, Robin leaped.

He soared lightly across the abyss and landed safely on the other side. He went on, slowly, carefully.

A spot of light appeared before him. He stared at it and continued moving forward. The light widened, became the end of the tunnel, became the entrance to something new. He hastened on and burst at last into a new cavern-world, the world of the next bubble.

It looked much like his old one, but it was definitely smaller. The rounded ceiling could be made out quite clearly and he estimated its diameter as not more than a half mile. The far side of the bubble could be seen clearly and this one, he noticed, even from where he stood, had many such clefts and cracks in the wall. It was, he supposed, either an older bubble, more cracked in the course of eons of moonquakes and heat changes, or else it was more tightly knitted in a close mass of such bubbles.

A thick jungle of giant Moontrees was growing here, stalklike plants resembling those he knew, but seemingly larger and more profuse. Robin started to walk through it toward the farther wall of the bubble. Cheeky had leaped into the stalks and was swinging through them ahead of him, when suddenly the monkey uttered a terrified shriek and there arose a strange high-pitched barking sound. Robin pushed through and saw the monkey, high in the top of a Moontree and a strange sort of Moonhound leaping for him. This kind of Moonhound was considerably bigger than the ones he had seen in his original bubble. It was uttering the eager bark of a hungry beast sighting its prey.

Robin unlimbered his bow and fitting an arrow into it, let fly. The sharp missile skewered the Moonbeast and the animal twisted in mid-air and fell thrashing to the ground. Robin dashed in and finished it off with a blow from the stone club he carried.

Cheeky came down from the tree cautiously, advanced to the dead animal, and prodded it. Then the monkey uttered a shriek, bared its teeth, and began to pommel the dead body as if he had been the one to bring it down.

Robin examined the animal. It was similar in many ways to the Moonhounds, yet different, and Robin's private theory that the Moonhound represented the equivalent of a mammal type seemed verified. Whereas the Moonhound was a wolf or dog, this creature corresponded more closely to a leopard or tiger.

The flesh of this creature seemed as if it might possibly make a substitute for leather--although it, too, was eerily transparent and it, too, possessed but one central eye and a large light organ.