Iceworld

firmly attached to the torpedo, he had seized the control spindle and shot straight upward. He was taking a chance, he realized; but with the relatively cold torpedo hull to smash the initial path through the thin overhanging branches he felt that he could avoid contact with any one of them except for periods too brief to set them ablaze. He succeeded, though a suspicion of smoke floated upward in his wake as he soared clear. The Karella, he noted, had done likewise; it now floated a quarter of a mile above the blaze it had started. He wasted no further time on recriminations, even though the chances seemed good that those on board would be listening again.

The fire was not spreading as rapidly as he had feared it might in most directions. On the side toward the house it seemed to have made no progress at all, while along the contours of the mountain its advance was very slow. Upward, however, under the combined influence of its own convection currents and the breeze which had already been blowing in that direction, it was leaping from growth to growth in fine style. Ken saw flaming bits of vegetable tissue borne far aloft on the hot air pillar; some burned out in flight, others settled into the trees farther up the mountain and gave rise to other centers of combustion. A dark-colored growth, apparently dead, a few yards in advance of the main blaze, smoked briefly in the fierce radiation and suddenly exploded with an audible roar, burning out in less then fifteen seconds and crumbling into a rain of glowing coals. Ken, unmoved by the prospect of being involved in the uprushing hot gases, maneuvered closer to the blazed At least part of the reason for the slow advance downhill became evident; the two natives with whom he had been talking were visible through the trees, spraying everything in sight with apparently tiny streams of a liquid at whose nature Ken could only make an educated guess. He watched them for some time, noting that they refilled their containers of liquid every few minutes at a stream of the stuff flowing down near the housed which Ken had not noticed earlier. He wondered where the liquid could have its source, and decided to follow the stream uphill to find out.

As he rose, the extent of the forest country once more was impressed on him, and he began to wonder at the magnitude of the catastrophe the Karella had caused If this combustion reaction were to spread over the whole countryside, the effect on the natives would undoubtedly be quite serious, he decided. He noted that it had spread across the little stream a short distance farther up; apparently the liquid had to be in actual contact with vegetation in order to stop combustion. The flame and smoke made it impossible to follow the watercourse; Ken dropped lower, reasoning with some justice that the temperature of his armor would do no damage to vegetation already burning, and drifted along only a few feet above the stream bed, barely able to see even then. For the first time he saw animal life other than the intelligent natives; tiny creatures, usually four-legged when they were moving slowly enough for him to see the legs, all fleeing madly uphill. Ken wondered that they could breath — the smoke suggested that the air should be full of combustion products, and probably was too hot for them; he knew nothing about the fairly common phenomenon of relatively pure air near the ground ahead of a fire. Large scale conflagrations occurred on Sarr, but he was no fireman.

He was ahead of the flames but still in smoke-filled air when he found the source of the stream. He had trouble realizing that it was the source; he was no geologist, and a real geologist of his race would have had difficulty in figuring out the mechanism of a spring. Ken rather suspected artificial backing for the phenomenon, but he did not dare touch the liquid to investigate very closely. He would have had grounds for serious worry had he known that a forest fire can sometimes cause a local rainstorm; but that, too, was too far outside his experience. The closest approach to such a thing on Sarr occurred near the poles, where on very rare occasions meteorological forces so combined as to raise the pressure and drop the temperature enough to cause a slight precipitation of liquid sulfur.

Realizing that nothing more could be learned here at the moment, Ken rose once more into clearer air. Downhill, the natives seemed to be winning; there was a narrow band of blackened vegetation at the edge of the region of flame which suggested that the fire had burned out in that direction. At the sides, progress was less obvious; but the fire in general had taken on the outline of a great fan, with its handle pointing toward the house and the ribs spreading to a breadth of three or four hundred yards at a roughly equal distance up the mountainside. Through the billowing smoke, Ken could see that the large trees were thinning out at this point, giving way to smaller growths which in turn seemed to follow the usual pattern of yielding to bare rock near the top of the hill. Ken, looking the situation over from his vantage point, decided that the blaze stood a very good chance of eating itself into starvation territory in a very few hours; the natives might very well dispose of the fringes without assistance.

The thought of possible assistance gave rise to another; the smoke was rising in a pillar that must be visible for many miles. Was this likely to bring other natives to help, or would it be mistaken for an ordinary cloud? Ken’s eyes, with their color balance differing as it did from the human, could not be sure of the distinction in hue; but the shape of the smoke pillar seemed distinctive enough to attract attention. With this thought in mind, he decided to call the ship; but when he looked up, the vessel was nowhere in sight. He moved the torpedo back and forth rapidly enough to cause his armor to swing pendulum fashion and give him a glimpse of the sky directly overhead, but there was still no sign of the black cylinder. Apparently Laj Drai’s brief taste of Planet Three had been enough. To make sure, Ken broadcast his thought on the matter of further natives arriving, and then returned to his examination of the fire. Within seconds, he had once more forgotten the vessel’s existence.

He had found that little could be seen inside the fire itself. This time, therefore, he descended just ahead of the actual blaze, watching through the eddying smoke clouds as the leaves of bushes and small trees in its path shriveled, smoked, and burst into flame sometimes many feet from the nearest actual tongue of fire. Usually, he noticed, the thicker stems did not ignite until they were actually in contact with flame from some other source, but there were exceptions to this. He remembered the exploding tree. He regretted that he had no thermometer, with which he could get some idea of the kindling point of the growths. He wondered if the oxygen alone could be responsible for such a furious reaction, or whether the nitrogen which made up such a large part of the atmosphere might be playing a part. It had combined with his titanium specimen, after all. There seemed no way of collecting samples of the combustion gases, but perhaps some of the solid residue would tell. Ken landed in the midst of the fire, brought the torpedo down beside him, opened the cargo door, and threw in several pieces of charred wood. Then he went downhill a short distance, located some grayish ash, and added that to the collection. Satisfied for the moment, he rose clear of the ground again, wondering vaguely how much time, if any, his brief sojourn in the flames would add to the few hours he could remain down. He had heard the thermostats in his armor cutting off several of the heaters during those few minutes; the outer layers must have been warmed up considerably.

In an attempt to guess how long the fire would take to burn out, Ken moved fifty or sixty yards ahead of the flame front and began timing its rate of progress at several points. This proved deceptive, since the rate of travel varied greatly — as any forester could have told him. It depended principally on the sort of fuel available in a given spot and on the configuration of the ground, which influenced the air currents feeding the fire; and those points were both too difficult to observe for Ken to learn very much about them. He gave up that attempt, moved a little farther ahead, and tried to see what he could of the animals still scurrying away from the most frightful menace that ever threatened their small lives.

It was here that the torpedo microphone picked up a cracking that differed from that of the fire, and a heavy panting that reminded Ken of the sounds he had heard just after his first meeting with Roger. Remembering that he had not seen two of the natives just after the blaze had started, the scientist became a trifle anxious; and two or three minutes’ search showed that his worry was only too well founded. Roger and Edith Wing, gasping and coughing from smoke and exhaustion, were struggling almost blindly through the bushes. The boy’s original intention had been to travel across the path of the blaze, to get out of its way — the most sensible course under the circumstances. Several things, however, had combined to make this a trifle difficult. For one thing, after the smoke had become thick enough to prevent their seeing more than a few yards, they had blundered into a little hollow. Using the slope of the ground for guidance, they had made several complete circles of this spot before realizing what had happened. By that time the flames were actually in sight, and they had no choice but to run straight before them. They simply did not know by then how wide the flame front was; to parallel it at a distance of only a few yards would have been the height of insanity. They had been trying to work their way to one side while keeping ahead of the flames, but they were rapidly approaching a state of exhaustion where merely keeping ahead demanded all that their young bodies could give. They were nearly blind, with tears streaming down their soot-stained faces. In Edith’s case the tears were not entirely due to smoke; she was crying openly from fatigue and terror, while the boy was having a good deal of trouble keeping his self-control.

None of these facts were very clear to the scientist, since even the undistorted human face was still quite