At eight-twenty, Lockley went to the electronic base line instrument which he was to use this morning. It was a modification of the devices used to clock artificial satellites in their orbits and measure their distance within inches from hundreds of miles away. The purpose was to make a really accurate map of the park. There were other instruments in other line-of-sight positions, very far away. Lockley's schedule called for them to measure their distances from each other some time this morning. Two were carefully placed on bench marks of the continental grid. In twenty minutes or so of cooperation, the distances of six such instruments could be measured with astonishing precision and tied in to the bench marks already scattered over the continent. Presently photographing planes would fly overhead, taking overlapping pictures from thirty thousand feet. They would show the survey points and the measurements between them would be exact, the photos could be used as stereo-pairs to take off contour lines, and in a few days there would be a map--a veritable cartographer's dream for accuracy and detail. That was the intention. But though Lockley hadn't heard of it yet, something was reported to have landed from space, and a shock like an impact was recorded, and all conditions would shortly be changed. It would be noted from the beginning, however, that an impact equal to a hundred-ton explosion was a very small shock for the landing of a bolide. It would add to the plausibility of reported deceleration, though, and would arouse acute suspicion. Justly so. At 8:20, Lockley called Sattell who was southeast of him. The measuring instruments used microwaves and gave readings of distance by counting cycles and reading phase differences. As a matter of convenience the microwaves could be modulated by a microphone, so the same instrument could be used for communication while measurements went on. But the microwaves were directed in a very tight beam. The device had to be aimed exactly right and a suitable reception instrument had to be at the target if it was to be used at all. Also, there was no signal to call a man to listen. He had to be listening beforehand, and with his instrument aimed right, too. So Lockley flipped the modulator switch and turned on the instrument. He said patiently, "Calling Sattell. Calling Sattell. Lockley calling Sattell." He repeated it some dozens of times. He was about to give it up and call Vale instead when Sattell answered. He'd slept a little later than Lockley. It was now close to nine o'clock. But Sattell had expected the call. They checked the functioning of their instruments against each other. "Right!" said Lockley at last. "I'll check with Vale and on out of the park, and then we'll put it all together and wrap it up and take it home."