by Hal Clement
The worst of his journey was behind. The narrow bridge of livable rock which led to the strange land he had found had been recrossed in safety, in spite of the terrifying and deceptive manner in which temblors from the earthquake zone far to the north were trapped, magnified, and echoed from its sides. Now he could see for many days’ travel all about him, and as far as he could see the land was good.
Not as good as that he had visited, of course. This was the land he had known all his life, where food was just hard enough to find to make life interesting; where for ages past counting other, less fortunate, races from the far, far north had sought to break in and kill that they might inherit its plenty; where pools of magma shifted just rapidly enough to trap the unwary between impenetrable basalt and glowing death; where, if Pentong was right in what he believed of his discovery, regions now too close to the zones of death might be made accessible and provide food and living space for unguessable generations to come.
He dreamt of this possibility constantly as he moved. No trace of his passage marked the rock behind him, for none of it was edible; but he hardly thought of food for himself. Speed was his prime concern, and to achieve it he traveled as close as he dared to the upper zones.
The nearest settlement was more than five thousand miles north, he knew; his memory held a sharp picture of the tortuous path he had followed from it, and he retraced that path now. It led him far to the east, where the earth tremors were faint and travel slowed by the poor vision; then back, at a much lower level, to the northwest, where the principal delay was the denser rock. Five hundred miles short of his goal he had to stop, to examine carefully the region of magma pools through which he had passed on his way south. The precise path he had followed could not now be used; it was blocked in several places by molten rock which had forced its way between strata and heated the otherwise habitable stone above and below to an unbearable degree. But other paths existed; and slowly and carefully Pentong wormed his way between the pools, sometimes retreating the way he had come, sometimes going almost straight away from his goal, but gradually working north and downward until the last of the dangerous pockets of fluid lay behind him. Then he could hasten once more; and at last he reached the bed of carbonate rock, a mile thick and more than thirty thousand square miles in area, which had been deposited on the floor of an ancient sea some hundreds of millions of years before and was now safely surrounded and capped by harder layers which shielded its inhabitants from filtering oxygen. This was the city—not the one where Pentong had been born, but the farthest south of all the dwelling centers of his people, and the one to which the more adventurous spirits of the race tended to gravitate. The cities to the northwest and northeast, under the Bering and Icelandic bridges, held danger, of course; they bore the brunt of the endless defense against the savage tribes from beyond the bridges. Still, that danger was known and almost routine; it was the unknown parts of the world that spelled adventure. Pentong, he was sure, had proved himself the most adventurous so far; and he was also sure that he had done more.
“Halt!” The challenge came through the rock as Pentong’s great, liquid body began to filter into the limestone. No city, even this far from the zones of war, dared be without sentries. “Name yourself!”
“I am Pentong, returning from the south, a trip that was commanded. My word is this.” He emitted the coded series of temblors which the City Leaders had given him for identification, when and if he returned.
“Wait.” The explorer knew that the sentry’s body extended far back into the city, and that at his other end he was in communication with the Leaders. The wait was not long. “Enter. You may eat, if you hunger, but go to the Leaders as soon thereafter as may be.”
“I am hungry, but I must go to them at once. I have found something of importance, and they must know.” The sentry was plainly curious, but forebore to question further; obviously if this stranger felt his news too important to wait for food. he would hardly pause for conversation.
“Take the Stratum of Manganese; it will be cleared for you,” was all the watcher said. Pentong acknowledged the courtesy—traffic was sometimes a problem in a city of sixty billion inhabitants, each of whom averaged ten cubic yards in volume and was apt to have that bulk spread through a most irregular outline. The Stratum of Manganese was a foot-thick layer stained with the oxide of that metal, and thereby marked plainly to Pentong’s senses. It was cut off sharply by a fault which extended across the center of the city in a northeast-southwest direction; and at one point along that fault was a large volume where numerous boulders of quartz, probably washed to this spot by some ancient river, were imbedded in the limestone. Here the Leaders, or enough of them to transact business, could always be found. Pentong greeted them, received the acknowledgment, and began his report without preamble.
“About five thousand miles to the south,” he said, “the continental mass in which this city is located narrows apparently to a point. The earthquake zone extends to this point, and seeing is good; but echoes tend to be confusing in some regions, and I explored many of these by touch. In one such area I found a long tongue of sandstone extending yet farther south; and after debating whether I should return to report its existence before venturing out along it, I decided it would be better to have something more complete to report. It was almost like traveling through a stratum which has been cut off on opposite sides by parallel dikes; but the sides this time were simply emptiness. There was no zone of death, however, apparently the tongue of rock is surrounded by what Derrell the Thinker called ocean, which seems to protect the upper regions of portions of the continents. Below, of course, was basalt.
“The neck of rock went on, seemingly without end. Sometimes it widened, sometimes narrowed so that I thought it had come to an end; but it always went on. Those who claim the continents are drifting will have to explain how that narrow ridge of stone has stayed intact.
“At last, however, it really widened; and to make short a report whose data was long in compiling, there is a continent at the other end—and I could find no trace of other than lower animals in that continent. That, however, is not its most important feature; what is really striking is the fact that it appears to have no Zone of Death whatever. It is covered with a solid material, which seems to be crystalline from the way it carries sound, but which is impenetrable to living bodies. The continent is inhabitable from top to bottom.”
“How about edible rock?”
“As good or better than our own land.” The Leaders reacted audibly to this, and it was some time before speech was again directed at the explorer. Then, as he had expected, it was complimentary.
“Pentong, you deserve the thanks of every inhabitant of this continent. If your report is as accurate as it seems to be objective, our food problem is solved for generations to come. We will transmit this news to the other cities, and plans for colonizing the new continent will be worked out as rapidly as may be. Your name will be known from here to the Northern Frontier.”
For a moment the explorer basked in the praise that was the deepest need of his kind; then he spoke again, with a delicious thrill of anticipation.
“Leaders, there is yet more, if I may speak.” Cracklings of surprise spread from the boulder-shot area, and the nearer citizens paused in their activities to learn what went on.
“Speak.”
“I was curious as to the nature of this solid which seemed as impenetrable as basalt, and strove to learn more about it. For a long time I made no progress; but at last I came to an earthquake zone, in which magma had risen very near the upper levels. About this point the strange substance was thinner; and while investigating the neighborhood, a pocket of magma broke through the Outer Void. This I could tell, partly because of the good seeing, and partly because I could feel the heat working down from the thin layers above.” He paused.
“This has occurred before,” commented one of the Leaders. “What did it teach you?”
“Where the magma spread, th
e solid disappeared—and became like the ocean!” Pentong stopped again, for purely rhetorical reasons—he knew there would be no interruption this time.
“As you all remember, Derrell the Thinker showed that ocean was a substance, apparently liquid like magma; he studied its sound-transmitting properties, and described them well. I heard his lecture, and examined the substance myself on several occasions. This crystalline sheath of the Southern Continent is simply solid ocean; it melted just as rock does when the magma reached it.” Again the pause, and this time the Leaders conferred briefly.
“Your point is of extreme scientific interest,” their spokesman finally said, “but we admit we do not see practical importance for it as yet. We gather from your manner that you do; if you would go on——” he left the sentence unfinished.
“My point is simple. Ocean protects rock from the oxygen, which filters down from the Void and kills those exposed to it—sometimes even renders rock poisonous. Much of our continent is protected by ocean, but much is not, and its upper layers are therefore unattainable. This solid ocean melts very easily, as I could see on the Southern Continent; and the continent seems to be covered with it to a depth of more than a mile, on the average. It may seem an ambitious project, but if that continent were to be heated enough to melt its ocean covering, would not it add to the ocean over the rest of the world and thus cover more of our continent?”
For long moments no answer came; Pentong could not tell whether the Leaders were actually considering the problem objectively or reacting emotionally to his admittedly audacious suggestion. The first response was in the form of a question.
“Just why should this material blanket the continents instead of remaining more or less where it is? You seem to be taking a good deal for granted.”
“I realize that the behavior of liquids such as magma and ocean out in the Void is not generally known,” responded Pentong. “However, there exists a good deal of observation which strongly suggests that magma, at least, tends to spread out over the surface of the Earth when released to the Void. I admit that further observation would be needed to prove that ocean does the same—but is it not already doing just that? It seems reasonable to suppose that the liquid ocean has spread as far as its quantity permits; if we add more, it should spread farther. Let us at least check this point; I can show the way, or for that matter describe it, to the Southern Continent, and the necessary experiments could be conducted by a small group.”
* * *
The news of the Pentong project took some time to reach Derrell the Thinker. There were several reasons for this; for one, he was located thousands of miles from the city under the Gulf of Mexico where Pentong had made his report, and for another he was in the midst of a battlefield. The latter fact was not at once evident; the only sights and sounds—the two were identical to Derrell, whose only long-range sense reacted to shock waves in the earth’s crust—were those emitted from the earthquake belt to the south and west. He himself was focusing his entire attention on a matter unconnected with the battle; but at least half of his research crew had their fluid bodies extended and joined into a single net that surrounded the entire area of the experiment. It was hoped that none of the savages from the Asian mainland would get through the net without touching one of its strands and betraying their presence.
The thing that interested Derrell was a cave, something almost unheard of in the depths where his people dwelt. Virtually all the empty spaces, which his people regarded as extensions of the Outer Void, were very close to that void; and they were almost without exception filled with the oxygen which poisoned the rocks for the dwellers of the depths. Occasional bubbles occurred in the igneous rocks, of course, filled with gases which had come from the rocks themselves; but as a rule these were unapproachable—the material in which they occurred was nearly impenetrable to the members of Derrell’s race, who traveled through rock rather as ink does through a blotter.
The present cave was one of the few exceptions to this rule. The rock itself was not porous enough for travel, but seismic strains had produced a network of miscroscopic cracks part way into the mass which permitted slow progress, if the traveler had persistence.
Derrell had seen caves before from a distance, but the thing he was watching now had never occurred within his memory or knowledge. The upper level of the bubble was just at the top of the igneous layer in which it had formed; the rock above was sedimentary. Between the two layers a thin sill was gradually making its way from a pool of magma a few miles distant—a pool that was being fed by energy from sources far below, and outside the bounds even of Derrell’s knowledge. It was more than likely that some day this sill might grow to the proportions of a laccolith, in view of the nature of the rock above; but this was not the scientist’s concern at the moment. The advancing magma was approaching the bubble, and he wanted to see what effect the trapped, high-pressure gas in the “empty” space would have on the molten rock. It was fortunate that this was occurring just here; the endless, tiny seismic shocks from the southwest made things clearly visible throughout the region. It would have been extremely dangerous, with the Asian savages filtering through the neighboring strata, if the investigators had had to produce sounds of their own in order to further their research.
Derrell had a mental picture of what would occur when the molten rock reached the bubble, but like any good scientist he was not allowing it to influence his observing technique. He intended to see everything that happened; and his attention was so completely centered on that particular volume of rock that the arrival of one of his assistants, who had been on a short leave to the nearest of the frontier cities, failed to distract him in the slightest. The assistant himself forbore to interrupt, though he had news that he knew would be of interest; for the magma was very close now to the bubble. Like the chief scientist, the newcomer had a mental picture of the hot fluids simply reaching the cavity, flowing around its walls, and gradually filling it from edge to center. Like Derrell, his idea of the general nature of gases was too sketchy to permit him to realize that, at the very least, the vapor in the bubble must dissolve in the inflowing rock before his picture could be carried through; and like his chief, he had no conception whatever of another force that would also operate. No living member of their race had ever had a good look at a fluid that was not in a confined space; they had never seen a free liquid surface. Their experience was about to be enlarged.
There would be no point in guessing who was the most surprised by what actually happened, but there was no doubt about which of the observers adjusted himself first. Derrell was paralyzed for just an instant as the first drops of fluid reached the opening of the cavity—and shot straight across it to the other side!—but he noted carefully and precisely how more of the magma followed. The drops became a stream, and gradually a pool of the stuff came into being against the side of the bubble opposite the opening. The sides of the pool not in contact with the walls of the cavity seemed to want to form a plane surface, but the stream that was adding to its volume gave rise to disturbances which spread from the point of impact in all directions over the surface—waves which none of the watchers had ever seen or imagined, and which held even the sentries’ attention to a degree which might have proven disastrous. Not until the bubble had filled completely with molten rock did anyone move, speak, or even think of anything but what was happening a few hundred yards away; and even then most of the team waited for Derrell to express an opinion. He, regarding his assistants as students to be guided by suggestion rather than laymen who might be impressed by spot conclusions, opened his comments with a question.
“Could the ordinary pressure on that liquid account for its behavior?”
“Not completely.” The answer came promptly from one of the team.
“Why not? Pressure can force liquid between rock layers, and even into rock pores; why could it not send a stream across a space where there is no resistance?”
“It could, I suppose; but I fail to see
how ordinary rock pressure could keep one side of that growing pool flat when the rock was not actually touching it. That would seem to call for some invisible substance pressing on that particular surface—a substance not only invisible, but able to permit the stream of rock to pass toward the new pool but not away from it. I find such a substance hard to imagine.”
“So do I. Your objection to rock pressure also seems valid—unless someone else can see a way?” He paused for a fair interval, but if any of the assistants had ideas they were not sufficiently formulated for expression. “It would seem, then, that some force with which we are unfamiliar is involved. That means that all the data anyone may have is possibly relevant. Karpor, list the material you have observed which you think might help.”
The student responded at once.
“The igneous rock is largely silicates of magnesium, the stratiform layer next to it mostly calcium carbonate. The bubble is about fifteen feet in diameter, one side almost exactly tangent to the stratiform boundary. The boundary itself is parallel to the Void boundary a mile and a half away. The front edge of the sill was advancing at about six inches an hour, and the sill itself had a thickness of about——”
“All right; good so far. Taless, what else?” Another student took up the list; and the recent arrival forgot his news temporarily in the intensity of the resulting discussion. By the time he remembered it, a hypothesis had been developed.
“It seems possible,” Derrell summed the idea up, “that a force of unknown nature exists, which tends to drive liquids (at least) as far from the Void as they are free to travel. Our single observation is to that effect, anyway. It would seem desirable to find other, more accessible hollows in the deeper rocks, to determine how far from the Void boundary this force extends, and to learn if possible whether other things than liquids are affected.”