"Lift it up," he said..
Bigman looked at him, bent, and lifted. For a moment he looked puzzled as the bulb remained where it was; then he yanked with all his might and still nothing happened.
He looked up angrily. "What did you do?"
David smiled. "When the safety is released, any pressure at the tip of the bulb releases a thin force-field about twelve inches long that cuts right into the rock. The end of the field then expands outward in each direction about six inches, to make a 'T' of force. The limits of the field are blunt, not sharp, so you can't loosen it by yanking it from side to side. The only way you can pull out the bulb is to break the rock clean off."
"How do you release it?"
David ran the hundred-foot length of ladder through his hands and came up with a similar bulb at the other end. He twisted it, then pushed it at the rock. It remained there, and after some fifteen seconds the first bulb fell on its side.
"If you activate one bulb," he said, "the other is automatically deactivated. Or, of course, if you adjust the safety catch of an activated bulb"-he bent down and did so-"it is deactivated"-he lifted it up-"and the other remains unaffected."
Bigman squatted. Where the two bulbs had been there were now narrow cuts about four inches long in the living rock. They were too narrow for him to insert his fingernail.
David Star was speaking. He said, "I've got water and food for a week. I'm afraid my oxygen won't last more than two days, but you wait a week anyway. If I'm not back then, this is the letter you're to deliver to the Council headquarters."
"Hold on. You don't really think these fairy-tale
Martians____________________ "
"I mean lots of things. I mean I may slip. The rope ladder may be faulty. I may accidentally anchor it to a point at which there is a fault in the rock. Anything. So can I rely on you?"
Bigman looked disappointed. "But that's a fine situation. Am I supposed to sit around up here while you take all the risks?"
"It's the way a team works, Bigman. You know that."
He was stooping at the lip of the fissure. The sun was edging over the horizon before them and the sky had faded from black to purple. The fissure, however, remained a forbidding dusky abyss. The sparse atmosphere of Mars did not scatter light very well, and only when the sun was directly overhead was the eternal night of the fissure dispelled.
Stolidly David tossed the ladder into the fissure. Its fiber made no noise as it swung against the rock, upheld by the knob which held tightly to the stony lip. A hundred feet below they could hear the other knob thump once or twice.
David yanked at the rope to test its hold, then, seizing the topmost rung with his hands, he vaulted into the abyss himself. It was a feathery feeling floating down at less than half the speed one would have on Earth, but there it ended. His actual weight was not far below Earth normal, considering the two oxygen cylinders he carried, each the largest size available at the farm.
His head projected above surface. Bigman was staring at him, wide-eyed. David said, "Now get away and take the car with you. Return the films and viewers to the Council and leave the scooter."
"Right," said Bigman. All cars carried emergency four-wheeled platforms that could travel fifty miles under their own power. They were uncomfortable and no protection at all against cold or, worse still, against dust storms. Still, when a sand-car broke down miles from home, scooters were better than waiting to be found.
David Starr looked downward. It was too dark to see the end of the ladder, the sheen of which glimmered into grayness. Allowing his legs to dangle free, he scrambled down the face of the cliff rung by rung, counting as he did so. At the eightieth rung he reached for the free end of the ladder and reeled it in after hooking an arm about and through a rung, leaving both hands free.
When the lower bulb was in his hand, he reached to the right and thrust it at the face of the cliff. It remained there. He yanked hard at it, and it held. Quickly he swung himself from his previous position to the branch of the rope ladder now dangling from the new anchor. One hand remained on the portion of the ladder he had left, waiting for it to give. When it did so, he swung it outward, so that the bulb from above would swing wide of himself as it fell.
He felt a slight pendulum effect upon himself as the bulb, which had been at the lip of the fissure thirty seconds before, now lashed back and forth some one hundred and eighty feet below the surface of Mars. He looked up. There was a broad swath of purple sky to be seen, but he knew it would get narrower with each rung he descended.
Down he went, and at every eighty rungs he set himself a new anchor, first to the right of the old one and then to the left, maintaining in general a straight passage downward.
Six hours had passed, and once again David paused for a bite of concentrated ration and a swig of water from his canteen. Catching his feet in rungs and relaxing the pressure on his arms was all he could do in the way of resting. Nowhere in all the descent had there been a horizontal ledge large enough for him to catch his breath upon. At least nowhere within the reach of Ms flashlight.
That was bad in other ways. It meant that the trip upward, supposing that there ever was to be a trip upward, would have to be made by the slow method of jabbing each bulb, in turn, at a spot as high as one could reach. It could be done and had been-on the Moon. On Mars the gravity was more than twice what it was on the Moon, and progress would be horribly slow, far slower than the journey down was. And that, David realized grimly, was slow enough. He could not be much more than a mile below surface.
Downward there was only black. Above, the now narrow streak of sky had brightened. David decided to wait. It was past eleven by his Earth-time watch, and that had fair significance on Mars, where the period of rotation was only half an hour longer than on Earth. The sun would soon be overhead.
He thought soberly that the maps of the Martian caverns were at best only rough approximations from the action of vibration waves under the planet's surface. With very slight errors existing he could be miles away from the true entrance into the caverns.
And then, too, there might be no entrances at all. The caverns might be purely natural phenomena, like the Carlsbad Caverns on Earth. Except, of course, that these Martian caverns were hundreds of miles across.
He waited, almost drowsily, hanging loosely over nothing, in darkness and silence. He flexed his numbed fingers. Even under the gloves, the Martian cold nipped. When he was descending, the activity kept him warm; when he waited, the cold burrowed in.
He had almost decided to renew his climbing to keep from freezing when he caught the first -approach of dim light. He looked up and saw the slowly descending dim yellow of sunlight. Over the lip of the fissure, into the small streak of sky that remained to his vision, the sun came. It took ten minutes for the light to increase to maximum, when the entire burning globe had become visible. Small though it was to an Earthman's eyes, its width was one quarter that of the fissure opening. David knew the light would last half an hour or less and that the darkness would return for twenty-four hours thereafter.
He looked about rapidly, swinging as he did so. The wall of the fissure was by no means straight. It was jagged, but it was everywhere vertical. It was as though a cut had been made into the Martian soil with a badly crimped knife, but one which cut straight down. The opposite wall was considerably closer than it had been at the surface, but David estimated that there would be at least another mile or two of descent before it would be close enough to touch.
Still, it all amounted to nothing. Nothing!
And then he saw the patch of blackness. David's breath whistled sharply. There was considerable blackness elsewhere. Wherever an outcropping of rock cast a shadow, there was blackness. It was just that this particular patch was rectangular. It had perfect, or what seemed to be perfect, right angles. It had to be artificial. It was like a door of some sort set into the rock.