all planets, they decided to make for a range of hills due north

and a few miles off, and to complete the circuit of the square in

returning to the Callisto. The soft wet sand was covered with

huge and curious tracks, doubtless made by creatures that had

come to the stream during the night to drink, and they noticed

with satisfaction as they set out that the fresher ones led off

in the direction in which they were going. For practice, they

blew off the heads of the boa-constrictors as they hung from the