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."

Sattell agreed. Lockley, rather absurdly, felt uncomfortable because
he was going to have to talk to Vale. He had nothing against the man,
but Vale was, in a way, his rival although Jill didn't know of his
folly and Vale could hardly guess it.

He signed off to Sattell and swung the base line instrument to make a
similar check with Vale. It was now ten minutes after nine. He aligned