all sturdy building
located in the center of the settlement. The colony was growing,
assuming an aspect of permanency. Hafner sat in his chair and looked
out over that growth with satisfaction.

"A good job on the mouse plague," he said.

The biologist nodded. "Not bad, except there shouldn't be any mice
here. Biological Survey--"

"Forget it," said the exec. "Everybody makes mistakes, even B. S." He
leaned back and looked seriously at the biologist. "I have a job I
need done. Just now I'm short of men. If you have no objections...."

[Illustration]

The exec was always short of men, would be until the planet was
overcrowded, and he would try to find someone to do the work his own
men should have done. Dano Marin was not directly responsible to
Hafner; he was on loan to the expedition from Biological Controls.
Still, it was a good idea to cooperate with the executive. He sighed.

"It's not as bad as you think," said Hafner, interpreting the sound
correctly. He smiled. "We've got the digger together. I want you to
run it."

Since it tied right in with his investigations, Dano Marin looked
relieved and showed it.

"Except for food, we have to import most of our supplies," Hafner
explained. "It's a long haul, and we've got to make use of everything
on the planet we can. We need oil. There are going to be a lot of
wheels turning, and every one of them will have to have oil. In time
we'll set up a synthetic plant, but if we can locate a productive
field now, it's to our advantage."

"You're assuming the geology of Glade is similar to Earth?"

Hafner waggled his hand. "Why not? It's a nicer twin of Earth."

Why not? Because you couldn't always tell from the surface, thought
Marin. It seemed like Earth, but was it? Here was a good chance to
find out the history of Glade.

Hafner stood up. "Any time you're ready, a technician will check you
out on the digger. Let me know before you go."

* * * * *

Actually, the digger wasn't a digger. It didn't move or otherwise
displace a gram of dirt or rock. It was a means of looking down below
the surface, to any practical depth. A large crawler, it was big
enough for a man to live in without discomfort for a week.

It carried an outsize ultrasonic generator and a device for directing
the beam into the planet. That was the sending apparatus. The
receiving end began with a large sonic lens which picked up sound
beams reflected from any desi