Mitsuitei had been almost right in his prediction that the pit would be full of water. Only the fact that the land sloped a trifle—they were not right on top of the little hill—had saved it. As it was, several feet of water were in the bottom, and a good deal of mud had washed in from the two sides facing the edges of the crack. The other two, much better braced by deep-reaching roots, had held firm.
After some thought, Lampert used the little robot again. He started it at the bottom of the pit on the downhill side and drove almost horizontally toward the river. The two hundred meters of "neck" permitted the mole to emerge from the slope farther down. When it was withdrawn, a small drain hole was obtained. Several more of these were drilled, and the pit lost its water fairly rapidly.
There was still the problem of getting into the crack itself, which of course would involve digging below the level of the drain holes. Lampert, using the same excavator which had made the pit itself, finally provided a fair solution by digging a set of ditches around the larger hole; and since the opening itself was quite well protected by over-hanging trees, Mitsuitei had only drainage from the surrounding soil to contend with.
Two hours after arriving, therefore, he had a relatively clear working space. The bottom of the pit was limestone, exposed by the complete removal of the overlying soil, some three meters square. Across it ran the crack, a trifle less than a meter wide, still packed with dirt. Everything was muddy—limestone, projecting roots, and Mitsuitei himself. A slender log with branches cut to ten-centimeter stubs leaned against one corner, forming a rough ladder and giving entrance and egress to and from the site.
The machinery which had done the original digging was at one side. Mitsuitei did not expect to need it again. He was now equipped with a hand shovel, and seemed about to use it. Lampert, standing at the edge of the pit, felt the incongruity, but managed not to laugh.
"Are you sure there's nothing I can do down there with you?" he asked.
"I'm afraid not. From now on I want every bit of dirt to pass under my own eyes."
"Are you going to try to throw it all up here as you finish?"
"No. That's the purpose of the extra pit area down here. I can get a long way down the joint, simply heaping the material on the rock. It's damp enough to pile quite steeply, too."
"How far down do you think you can get? The crack's rather narrow to work in, and you have three and a half meters to go before you hit tuff. That's going to be rough shoveling. I still think you could use the machine safely for a little way further, at least."
"No doubt I could, but I'm not going to. There's one thing I might use, though. If you have another of those saws, such as the bonemen are using up on the cliff, I could widen this crack as I go—cut steps, in fact, to help get the mud up to this level when I'm further down."
"That's a good thought, but I don't have any other. If you really get far enough down to need it, though, I could fly up to get it. They were going to shift over to hand labor anyway."
"All right. Of course, it will be some time before I get that deep anyway; maybe I won't need it today." He bent to his work.
"But what do I do?" asked Lampert. "I can't go off to attend to my own projects, because String has to stay here to guard you. I can't get to the site where the others are working because I can't land there. I can't sit in the helicopter and twiddle my thumbs because I'll go crazy before the day is over." Mitsuitei straightened once more, and thought briefly.
"Is there nothing in the geophysical line you could do within sight of this pit?" he asked finally. "The saw and digging machine are not the only apparatus you brought."
"That's true. I brought some seismic gear, though I didn't plan to use it quite like this. I might map the formations under this hill. The information will be usable, I should think, and the joints will give quite a calibrating job. It will keep me busy, anyway."
"Just a minute!" Mitsuitei looked a trifle perturbed. "Does that mean you're going to set off explosives around here? I want the sides of this pit held up by something better than roots, if you do."
Lampert chuckled. "No explosives," he said. "This is a nice little gadget with a robot like the core sampler. It puts out waves of any type desired from any depth down to two hundred fifty meters—a sort of subterranean sonar. You'll never know it's working. The wave amplitude isn't enough to feel." He turned toward the helicopter on the river bank below, and was starting to walk toward it when McLaughlin interrupted. The guide had heard the conversation, and his question was purely rhetorical.
"You weren't planning to walk down to the flyer alone, were you, Doctor?"
"Well, yes, as a matter of fact. After all, I won't be working; I can keep my eyes open as I go. You can see me for the greater part of the journey from here, too."
Rather to his surprise the guide approved this argument, after a moment's thought.
"All right. But please keep your gun in your hand as well as your head on a swivel. I'd prefer to have Dr. Mitsuitei come down with us so we could stay together, but I know how he'd react to the interruption, and I realize you're not a kid. Just be careful."
Lampert promised; and the guide's manner had impressed him to the point where he was almost afraid to make the return journey, after reaching the flyer and packing his new equipment. He was rather surprised to get back to the site without being attacked, and McLaughlin's very evident relief at seeing him did nothing to ease his feelings.
He began to set up the machinery. This consisted of an assembly very similar to the drilling mole—a small delving robot drawing a slender tail behind it, the tail wound on a drum which surrounded the control unit. A dozen smaller cylinders reposed in attached clips.
"The attached borer," Lampert explained to the guide, "goes down to any depth I set, up to two hundred fifty meters. It can produce any of the three normal types of earthquake wave, singly or in any combination, with sufficient intensity to be detected at a range of over two kilometers in reasonably well-conducting rock. The small cylinders are detectors, equipped not only to receive and analyze the wave coming through the ground but to measure electronically their location with respect to each other and the main station. I can use as many of them as I please, up to the full dozen; but they can be planted only a little way below the surface. There exists equipment for getting readings at depths comparable to that of the transmitter, but I don't have it. As it stands, by spotting the receivers carefully I can get a pretty good picture of the formations for a radius of a kilometer and a depth even greater with ten minutes measuring—and ten hours computing."
"How far out do you plan to place these receivers?" the guide asked pointedly.
"Well—I hadn't made a detailed plan of that. I'd rather like to have them in radiating lines of three, the lines spreading about fifteen degrees, and the individual cylinders about two hundred meters apart."
"And just how were you going to place them? I gather that someone has to walk the best part of four kilometers—or do these things fly, in addition to their other abilities?"
"Er—someone walks. I thought perhaps, since you don't like the idea of my going alone through the jungle, that I might stand guard over Take in the pit while you set them out."
"Hmm." The guide did not explode, to Lampert's relief. It had not occurred to the scientist that the job of wandering around a hole in the ground waiting for animals which never came might get a little boring to a man of McLaughlin's background. "Let's go over first and see how Dr. Mitsuitei is getting along. I guess you could stand over him with a gun for half an hour. Of course, the cover runs dangerously close to the pit. Maybe we'd better burn it off to a safer distance—still, I guess that won't be necessary. You can stand out here where it's relatively clear, and see all the approaches to the pit. Something might jump in without your having time to hit it, and you'd at least see it and could get there fast enough to do any shooting necessary."
They approached the hole and looked in. Mitsuitei was working busily. A fair quantity of earth lay spread on the rock, and some two thirds of the length of the crack had been excavated to a depth of perhaps a quarter of a meter. The geophysicist attracted the little man's attention and told him of the plan; Mitsuitei nodded and bent once more to his work.
The Felodon was becoming restless. It could hardly be hungry as yet; but it was on its feet, snarling silently as it had when the helicopter first entered its ken. For perhaps a minute it stood; then, with the same air of determination it had shown days before and scores of kilometers away, it began to thread its way through the underbrush toward the river—and the digging site.
"I'll stand where you suggested, and never take my eyes off............