Chapter III: Part 3

The water coming from the underground falls rushed out to form a wide, shallow river which flowed along one side of the cavern and widened out to a few hundred feet clear across to the farther wall. On Robin's side the floor of the cavern rose in a slow slope until it reached its wall perhaps three hundred feet away. Robin could not estimate the length of the cavern. Looking along the river bank, the cave seemed to become veiled in a general mistiness and gathering darkness.

The light itself came from no definite source, but seemed to emanate from the rocky walls and ceiling, from the clayey ground, and from the general atmosphere. Robin supposed that the source was a natural phosphorescence which he knew was not too uncommon even in Terrestrial caverns.

All around on the soil bordering the flowing water was a forest, a forest with the weirdest vegetation Robin had ever seen. Plants growing in clumps and clusters, plants whose large treelike stalks resembled a whitish-blue bamboo, and which burst into globular blue bulbs which seemed to serve as leaves. Among these tree-sized growths was a rich undergrowth of tight balls of varying yellow and green and purple, growing like thick, squat mushrooms. And everywhere else a thick, lush carpet of green, not grasslike but rather like some oversize moss.

In this forest there were no sounds of birds or animals, but only that of plants swaying in the river breeze, the rushing of the waters, and from somewhere distant in the unseen end of the cavern a strange, steady hissing sound.

The rocket, or what was left of it, lay wedged against a section of the bank, its nose up and its tail swaying in the current. Robin looked at it, amazed to find it so small. All that was left of the rocket was the cargo nose, which was the only part sent off after the last of the rocket sections had discharged their forces and been dropped off. The whole affair was not more than about ten feet long, from the battered, blunted red nose, from which several long, straggling orange cords hung--all that was left of the parachute and its attachments--down to the scraped and battered white cylinder that was the cargo compartment. The compartment ended in a flat plate which bore only a few wires that had once connected it with the break-away mechanism of the last of the atomic blasting chambers. This alone was the load of the eight-story tower of energy which had been the Red Sands experimental rocket.

Robin, without further delay, bent down to the cylinder and began to haul and push it entirely out of the water to the dry ground. He knew he could not afford to risk its loss. To his surprise, moving the rocket head was an easy task. It was extremely light and he found himself possessed of tremendous strength, tired and bruised and sore as he was.

It was, he thought, as he pulled the rocket along, the Moon and its weak gravity. He would only weigh a sixth of his Earth weight here, so would the cargo head, yet he would have the muscles necessary for much more than that weight. He would literally be a superman here--if he could survive.

Survival, he knew, would be the question. He didn't know whether even now he might be inhaling poison from the strange, thin sublunar air. He didn't know what mysterious radioactive rays might be bathing him with their baleful influence. He didn't know whether any of the vegetation in this cavern world would be edible.

Having brought the cargo cylinder to a safe spot many feet from the water, Robin looked for the door that would open the animal compartment. He found it, forced it open. Inside were the two cages. Gently he reached in, unscrewed them from their holdings, and lifted them out.

One of the monkeys was dead, probably killed by some of the jouncing the rocket had taken. The other, looking miserable, was clinging to the bars chattering. Robin looked at it, and the monkey looked back. The young man unlatched the cage, reached in, and took the little brown animal by the back of the neck. But the monkey made no effort to bite. Instead, it twisted around, grabbed Robin's arm, and hung tight.

When his grip was released, the monkey scurried up Robin's arm and clung to his shoulder, recognizing the need for companionship after its frightening experiences.

The rabbits had fared slightly better. One of them was dead, but the other three, while somewhat beaten around, were alive and sniffling their pink noses. Robin saw that there was very little food or water left for the animals.

Here then was the means to test the Moon's capacity to produce food and drink. First, however, Robin decided he would build a pen for the rabbits. If he were lucky, he could breed them and have at least one source of food suited to his system.

He went over to the nearest clump of ball-trees, looked them over, tested his strength on them. They broke easily and quickly when he grasped one by the trunk and pulled. He found that it could be splintered into shreds fairly rapidly and that inside the shell of the stalk was a mass of cottony matter.

He shredded a number of the stalks, and then staked them out in the ground to make a small fenced pen, tying the whole together with one of the long cords hanging from the parachute nose. Into this makeshift pen, he released the three rabbits. He filled the cup from their cage with water from the river, placed it in the pen. The rabbits hopped over, sniffed, and drank. They seemed to suffer no ill effects.

Robin broke open one of the ball-like growths from the tree, found it contained a substance resembling a combination of melon and potato. He offered some of this to the rabbits and after an interval they ate it and seemed to like it.

The monkey was chattering away as Robin did this and suddenly scampered down and snatched a piece of the ball-food, stuffing it into its mouth. Robin had not wanted to use the little creature for a test but the damage was done. However, the monkey seemed to enjoy it.

Robin sat down on the ground and watched. He felt tired, now realized just how tired he was, how sorely he ached from his experience. He felt warm and headachy now that the strain was over. He knew he still had things to do. He wanted to try to make a fire and cook the rabbit that had been killed. He was thirsty as well. He wanted to tie a cord to the monkey so that the animal would not run away into the unknown and possibly dangerous regions of the cavern. He wanted to find a safe place to sleep and hide should there be some sort of animal life around.

But he was growing terribly sleepy and feeling quite sick. He curled up, and before he could stop himself, he was asleep.

The rabbits nibbled on. The monkey sat on a ball in one of the strange trees and watched in silence. Far off, somewhere in the cavern, the mysterious hissing continued.

_8. Robinson Crusoe Carew_

When Robin Carew opened his eyes, he knew he was a very sick man. He felt warm, sticky, and he hurt all over. He tried to sit up, but everything spun dizzily around him. His arms, legs, and body were burning intolerably and there was an itch throughout him that he could do nothing about. He lay back, trying to gain strength.

A little later he managed to crawl to the water's edge, fill the container he had used in the trip from Earth, drag himself back. For a period whose length he could not determine he lay helpless in fever and pain, arousing himself only long enough to drink to soothe his tortured body.

Finally, the fever broke. He sat up, feeling weak but with his mind clear at long last. He dragged himself to his feet, blessing the light gravity, aware that if he were back home his body would not have responded. He felt that he was gaunt, he knew he had been through a terrible siege, and he could only guess at the time he had lain there, tossing about on the strange Lunar ground, unprotected in the queer climate of this unknown cavern. It must, he felt, have been days--Earth days, of course--that his attack had lasted.

Later on he decided that he had suffered from a severe case of space burn. Having traveled through the emptiness of the void between the planets, the vessel had been nearly unprotected from the cosmic rays and the more penetrating of the sun's invisible rays. He considered himself lucky to have survived at all.

He desperately needed food now to rebuild his body. He looked at the rabbit pen. The little animals were there and evidently prospering on the ball-food he had prepared for them before his sickness. It was almost all gone and he broke open and pared more at once. He wondered how long it would be before the animals bred--he knew that rabbits bred fast and abundantly, and hoped it would hold true on the Moon.

There was a sudden chattering in one of the strange trees and he looked up to see a little brown face peering at him. In a moment, the monkey leaped to the ground, then leaped in one tremendous jump to Robin's shoulder and perched there happy at finding companionship again. The monkey looked none the worse for its experience and evidently was getting along nicely on the Lunar vegetation. Thus encouraged, Robin fed himself, first carefully testing everything on the monkey, who objected to nothing.

But somehow the food was not entirely satisfying to the man, who felt that he needed more than that to recover his full energy. He looked again at the rabbits, looked also for the carcass of the dead one. But he found that part of it had rotted and part had been consumed. He looked closely and saw his first glimpse of a Lunar counterpart to animal life.

There were many tiny creatures, a half inch to an inch in length, looking at first like ants but on closer inspection appearing more like three-segmented worms, for they lacked legs and moved in an inchworm's fashion. Instead of antennae, each little worm-ant had on its front segment a single upstanding stalk ending in a little yellow ball. Robin touched one of these and it glowed momentarily. An organ of light, he thought, something like the ones carried by deep-sea fishes. The tiny things were eating the dead rabbit.

Robbin went back and examined the three remaining rabbits. Two were males and the female was evidently heavy with young. Well, he could afford to dispense with one of the males, then, for he knew his body needed meat.

He put the rabbit back though, realizing that first he must make a fire and determine how to cook his meal. He searched his pockets. He was wearing the GI jacket he'd taken from the soldier in Las Cruces. As he had hoped, he dug up a pack of matches in one pocket. He turned it over in thought. When this pack was used up, how could he make fire?

He piled some trunks of dead tree stalks in a cleared spot; he lit them with one of his matches. They caught fire rapidly and soon he had a nice blaze going. He watched the smoke rise and saw that it drifted rapidly away in the same direction the current was flowing--evidence of more caverns somewhere beyond.

He opened his scout knife, hesitated. He'd never cooked a rabbit before. In fact, he'd never had occasion to cook anything for himself. It was meat, he thought, and even if it were eaten raw--well, savages did, so he, too, could manage. He thought about boiling it in water, then realized that the light air pressure might allow water to boil without getting the necessary cooking effects. The best method therefore was to fry it where he could observe the progress.

Steeling himself, he seized the rabbit, killed and skinned it, the latter a process which he found thoroughly unpleasant. Cleaning it of its entrails, another unpleasant task, he cut the meat up into sizable chunks, skewered a couple of pieces on a metal rod which had been part of one of the cages from the rocket, and sat down to cook it over the open fire.

It turned out to be a longer job than he'd thought, and he burned the meat quite thoroughly in the process, but finally he made it edible and chewed it slowly. He needed salt, he realized, and wondered if he could find any. This would have priority when he began his explorations.

He hung the balance of the meat on a ball-tree with a piece of cord. He had seen no evidence of flying insects or creatures, and hoped thereby to be able to preserve the rest of the meat.

Thus fed, he sat down and began to map out his course. I must do things systematically, he told himself. I must keep track of time, set up a regular pattern of living, find a permanent base of operations. I shall have to explore this cavern and those beyond it, find all possible enemies and invent ways and means of defending myself. I shall have to breed my rabbits in quantity, find a way of using their pelts and fur. I shall have to determine a use for everything left from the rocket's material--metals and the like.

For, he continued telling himself, my one aim shall be to stay alive long enough to be found some day by exploring rockets from Earth. I am a Robinson Crusoe of a new world. Crusoe waited twenty-eight years for rescue, I must be as courageous. In his case, he had no evidence that any ship would ever bother to call on him. In my case I know that rockets are being made that will eventually lead to further Moon trips. I know that men are planning to come here. I must wait it out, even for twenty-eight years.

But it was not that simple and he knew it. But first things first, and the first task was to survive.

With the monkey scampering on ahead, he set out to walk to the cavern wall. He found it to be dark and glistening, a lavalike sheet resembling the bubble it was. Leaning against it and looking upward, he saw that it curved gradually up, and that indeed he was in a flaw within a very porous world. Like the inside of a Clark candy bar, he thought, with a wry smile.

Astronomers on Earth had always been puzzled by the lightness of the Moon. They had speculated on it as being mainly pumice. Lately there had been much speculation and opinion holding forth the theory that the Moon was porous, had these bubbles and air pockets all through it, that the Moon's water and atmosphere had all gone underground to be sealed off in these hollow spaces. He now knew they were right.

Most of these Moon bubbles, large enough to hold cities, must be entirely sealed off. But others were linked, sometimes broken into by quakes or the volcanic action which was still going on in the depths of what had once been considered a dead world. This particular cavern was such a bubble.

Robin walked along the outer wall and saw a dark black spot in it, and then others. He came to them, found they were breaks in the surface, pocks caused by smaller bubbles. He looked into one that opened at the base. Using his flashlight, he could see that it was a small, almost entirely spherical cave. He found others pocking the walls of the cavern bubble.

This then was the ideal spot for a permanent home. Not that he needed shielding from the elements, for obviously there were no elements here--no rain, snow, clouds, or weather oddities. Neither was there night or day.

Robin would move his possessions into this cave, simply to have them located and safe. Besides, there might be some larger form of life, some carnivores around--he could not tell. Better to be safe than sorry, he said to himself.

He acted at once, carrying the rocket nose and its stuff to the cave, transferring his rabbits and their pen to a spot just outside the cave door. He would need a bowl for water and, using his screwdriver blade, he finally managed to detach the curved rocket nose and found himself in possession of a deep bowl. He took this down to the water, filled it and carried it back to his cave.

Already he began to feel cheerier. Nothing like work, he thought, to take your mind off your other problems. Suddenly he realized he was tired.

How long had he been at this? He did not know. Now he realized that with no sunrise or sunset visible in his underground world, he could not tell time. He looked at his wrist watch, but it had stopped running, of course. He decided to take a nap; he lay down and fell asleep.

When he woke up, he set his watch at eight o'clock, decided to consider this the beginning of a day. He found the notebook he'd carried in his back pocket, opened it, and set up his new calendar. Using the date of the rocket's take-off, he allowed five days as a probable estimate of the time passed since. He had no means of knowing how long he had been ill, he suspected it had been longer, but decided to let it stand. After arriving at the date, he made the time eight in the morning, laid out the times he expected to eat, to work, to sleep. He would try to live according to a full Terrestrial day, checking the passage of time by his watch.

He then listed all the things he expected would have to be done, and decided to check them off as he completed them. Next he ate breakfast from the fruit of the ball-tree. He spent the rest of that morning trying to find a means of making fire. He had some bits of steel from the rocket, and he tried to strike sparks on everything that resembled rock. After a search, he found some fragments of rock near the water that gave off a spark. Whether these were flints or not, he did not care, so long as they worked for him.

With this discovery he knew he would be free from worry about the problem of matches. His next problem was to secure a weapon. This solved itself rather fast with a bow and arrow. A long, flexible metal tube from the rear connections of the rocket, bent to make a bow when tied with a string of nylon cord, made a satisfactory _twang_ when pulled. He made arrows out of the fibers of the Moontree stalks, and practiced shooting.

The next few days followed the same pattern. Robin enlarged his area of exploration, finding several other kinds of Lunar vegetation and a number of other insect-worms. He found several that were quite large, one as large as a squirrel. It was an odd thing, humping itself along in little bounds--a creature of a dozen ball-like segments, two of which had toothed mouths, although only the ball in front had an eye, a lidless orb set in the center of this ball. But the creature was fringed with the light-rod organs as the tiny worm-ants had been.

Robin tried to cook part of this creature but the monkey refused to touch it and he found it entirely unpalatable. On the other hand, he found that when he removed the little yellow balls from the top of the light stalks on the creature, they remained glowing--even as do the abdomens of fireflies. He therefore diligently set about catching a number of these Moonrats, as he named them, and making a lantern for himself by filling a glass tube with the glow organs. This worked out quite nicely when he experimented in his dark cave-home, emitting a clear, though pale, yellow light.

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.

Robin trekked on through this jungle until at last he reached the opposite wall. He was aware as he walked that there was a good deal of native life here, much more than had been evident in his own cavern. Evidently the first bubble was pretty much cut off from the general labyrinth of sublunar caverns. For as Robin walked, he caught glimpses of other Moonbeasts, slipping in and out, sometimes surprised and scurrying away. Moonworms, the equivalent of Earth's insect life, were here in plenty too, and there were many giant growths which were different from those in his own cave, and some fruits of considerable promise were growing on them.

"We could do some farming now," said Robin to Cheeky. "I'll bring back some of the seeds from these bigger trees and plant them back home. It'll give us some variety."

The monkey merely chattered and pushed on ahead.

At the farther wall, the original observation of many cracks was confirmed. The wall was broken like an eggshell and Robin could see that dozens of tunnels went out, probably leading to several other bubbles. He decided that the following day he would look for the ones that seemed to lead upward. But it was the time for sleep again.

He found a little cave, similar to the ones in which he had made his home, and there he and Cheeky ate their meal, cooking some of the meat from the Moontiger over a small open fire. The meat looked strange in its almost glassy appearance, yet it browned and tasted very good.

A thin stream of water meandered out of one of the cracks and from this Robin drank and refilled his canteen. He and the monkey curled up, now fed and contented, and went to sleep.

Robin awoke suddenly. He opened his eyes, puzzled. The monkey was screeching somewhere. He sat up, called, "Cheeky!"

The little creature dashed back to him. It had been outside the cave and it was excited. It was chattering and complaining as never before. The monkey jumped up and down in a perfect ecstasy of fury. Robin looked at it in wonder. He'd never seen Cheeky so excited. He sat up, looked around.

At first he saw nothing unusual. Outside the cave all was quiet. Then he noticed that his food pack had been moved. It had been dragged outside the cave, and its contents pulled out.

Robin got to his feet, went to it. Something had come into the cave silently, had taken the sack, and had examined its contents. He looked about, amazed and wondering.

Now he saw that other things had been touched. His canteen had been rolled over and the stopper unplugged. The water that had been inside was a little puddle on the cave floor.

Alarmed, Robin strung his bow, notched an arrow, and looked carefully around at the surrounding vegetation. Something was there, something big and cunning.

His eyes searched the ground and then he saw an outline in water from the canteen. Whatever it was had stepped into the puddle and then walked out of the cave. Robin saw a series of footprints.

Something that walked on two legs, something that took steps with a man-sized stride, something with three toes on each foot, that walked upright, was able to open bottles, look into sacks, and spy on sleeping strangers.

Something that might well be to the Moontiger and the Moonhound what Earth man was to the Earth tiger and the Earth hound. Moonman!

_11. The Glass Man_

The situation was so astonishing that for a while Robin did not do anything but sit down inside his cave and catch his breath. Somehow he had assumed all along that he would not find anything on a human scale on the Moon. His life had been mainly confined to the first cavern-bubble he'd arrived at and this, as he now realized, had been a rather isolated one.

Unconsciously, he had assumed that life in other protected airtight sublunar areas would be on a similarly low and limited level. Now he realized that he had had no right to make such an assumption. The Moon might harbor thousands and tens of thousands of bubbles; some might be hundreds of miles in scale; some, lower down, nearer the still-warm volcanic heart of the satellite, might even approach tropical climates and show little of the semi-monthly seasonal changes. In such places life might grow in profusion, might compel the kind of battle for existence as would bring out the evolution of a brain-carrying creature living on its wits.

And, although he was probably a little farther away from the central caverns at this moment, he was actually on the outskirts of the linked bubbles. In such border regions he might indeed encounter rovers and wanderers from the more prolific areas.

But the problem was now how to find this prowler. There was, he hoped, only one of them. The creature was probably hanging around somewhere, even now, keeping an eye on Robin's doings.

Robin got to his feet, looked through his provisions. He found a bit of rabbit meat, took it out, and skewered it on a cooking stick. He then knelt inside his cave-refuge and built a fire, using his flint and steel. Over this fire he hung the bit of meat and set it to roasting. He carefully began to fan the smoke out of the cave, knowing that it would carry the new and tongue-tempting odor of cooked meat to everything in the vicinity.

Robin slipped out of the cave and hid himself in a thick clump of growth nearby. Cheeky clung to his shoulder, hushed to silence. They waited.

After a few minutes Robin saw a slight motion in the vegetation at the other side of the cave entrance. He watched, and a moment later saw a head thrust itself out, and then a figure emerge and silently stalk to the cave and look in. It was manlike, walking on two feet and it had two arms. It was oddly misty, seeming naked and semi-transparent like the other animal life.

In one hand the creature carried a long stick to which something sharp and glassy was attached--clearly a type of spear. The creature paused at the cave mouth, then seeing no one within and unable to resist the tantalizing curiosity of cooking meat and a small fire, it went inside.

Immediately Robin dashed out of hiding, ran across the small space and blocked the entrance of the cave with his body. The creature within was bending over the meat, but on hearing Robin, it turned, and made a wild dash for the cave mouth.

It collided with Robin. For a moment there was a wild scramble of arms and legs and then Robin's greatly superior Earth muscles overpowered the other's and the creature was caught. Robin held it tightly in his arms, carried it into the cave, and sat it down.

The spear had been knocked aside in the tussle and Robin looked at it with a glance. One glance was enough to make the young man realize that he had had a narrow escape. Its tip was bright and as sharp as a piece of broken glass. If the creature had thought to jab that spear, it might have been deadly.