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 according to their own traditions they had achieved a union or symbiosis with the wild life of the planet and had abandoned such mechanical aids as unnecessary. Riordan snorted.