The nature of these arrangements was clear, after the native had gotten far enough ahead to permit a close inspection. They were booby traps, designed to drive a stone point into the body of anything attempting to follow hi the creature’s footsteps. They must have been intended against animals rather than other natives, since they could easily be avoided merely by paralleling the trail instead of following it.

The fact that the precaution was being taken at all, however, made the whole situation extremely interesting, and the robot was made to follow with all possible caution. The native traveled five or six miles in this fashion, and during this time set about forty of the traps. The robot avoided these without trouble, but several times tripped others which had apparently been set earlier. The blades did no harm to the machine; some of them actually broke against the plastic. It began to look as though the whole neighborhood had been “mined,” however.

Eventually the trail led to a rounded hill. The native climbed this quickly, and paused at a narrow gully opening near the top. It seemed to be looking around for followers, though no organs of vision had yet been identified by the human watchers. Apparently satisfied, it drew an ellipsoidal object from its sack, examined it carefully with delicate fingers, and then disappeared into the gully.

In two or three minutes it was back, this time without its grapefruit-size burden. Heading down the hill once more, it avoided with care both its own traps and the others, and set off in a direction different from that of its approach.