The traveler paid no attention, did not alter its steady pace of a couple of miles per hour. It measured about twelve inches long over all; its paddle-wheel-like extremities were perhaps two inches wide and three inches in diameter.

"Do you think it's actually alive, sir? In a place like this?"

"I'm sure of it. Watch carefully."

It struck the barrier and stopped. That is, its forward motion stopped, but its rolling did not. Its rate of revolution did not change; it either did not know or did not care that its drivers were slipping on the smooth, hard sand; that it could not climb the vertical metal plate; that it was not getting anywhere.

"What a brain!" Northrop chortled, squatting down closer. "Why doesn't it back up or turn around? It may be alive, but it certainly isn't very bright."

The creature, now in the shadow of the 'Troncist's helmet, slowed down abruptly - - went limp -- collapsed.

"Get out of his light!" Jack snapped, and pushed his friend violently away; and as the vicious sunlight struck it, the native revived and began to revolve as vigorously as before. "I've got a hunch. Sounds screwy -- never heard of such a thing -- but it acts like an energy-converter. Eats energy, raw and straight. No storage capacity -- on this world he wouldn't need it -- a few more seconds in the shade would probably have killed him, but there's no shade here. Therefore, he can't be dangerous."