taking chances. Riordan set a timer on the
boat's radio. If he didn't come back within two weeks to turn it off,
it would emit a signal which Wisby would hear, and he'd be rescued.

He checked his other equipment. He had an airsuit designed for Martian
conditions, with a small pump operated by a power-beam from the boat
to compress the atmosphere sufficiently for him to breathe it. The
same unit recovered enough water from his breath so that the weight of
supplies for several days was, in Martian gravity, not too great for
him to bear. He had a .45 rifle built to shoot in Martian air, that
was heavy enough for his purposes. And, of course, compass and
binoculars and sleeping bag. Pretty light equipment, but he preferred
a minimum anyway.

For ultimate emergencies there was the little tank of suspensine. By
turning a valve, he could release it into his air system. The gas
didn't exactly induce suspended animation, but it paralyzed efferent
nerves and slowed the overall metabolism to a point where a man could
live for weeks on one lungful of air. It was useful in surgery, and
had saved the life of more than one interplanetary explorer whose
oxygen system went awry. But Riordan didn't expect to have to use it.
He certainly hoped he wouldn't. It would be tedious to lie fully
conscious for days waiting for the automatic signal to call Wisby.

He stepped out of the boat and locked it. No danger that the owlie
would break in if he should double back; it would take tordenite to
crack that hull.

He whistled to his animals. They were native beasts, long ago
domesticated by the Martians and later by man. The rockhound was like
a gaunt wolf, but huge-breasted and feathered, a tracker as good as
any Terrestrial bloodhound. The "hawk" had less resemblance to its
counterpart of Earth: it was a bird of prey, but in the tenuous
atmosphere it needed a six-foot wingspread to lift its small body.
Riordan was pleased with their training.

The hound bayed, a low quavering note which would have been muffled
almost to inaudibility by the thin air and the man's plastic helmet
had the suit not included microphones and amplifiers. It circled,
sniffing, while the hawk rose into the alien sky.

Riordan did not look closely at the tower. It was a crumbling stump
atop a rusty hill, unhuman and grotesque. Once, perhaps ten thousand
years ago, the Martians had had a civilization of sorts, cities and
agriculture and a neolithic technology. But