the horizon, but it wasn't. It was behind him, a little closer than the first. He hit it with one shot.

Now Jonner had only the oxygen in his spacesuit tanks.

Jonner had made no effort to move farther away. He was still visible on the horizon, from the knees up, moving in a great circle around the personnel sphere.

Kraag aimed carefully and fired. He did not know the projectile's speed, but certainly it would be much faster than Jonner's rocks. After half a minute had passed, he knew he had missed.

There was only one thing to do. He settled himself and fired again, trying to lead Jonner slightly. Again he missed.

Methodically, taking his time, Kraag fired. Jonner walked on unconcernedly, circling. Kraag tried to fire so the path of his projectile would strike at the top of Jonner's strides, for then Jonner rose several feet into the air and his whole body was visible.

Occasionally, Jonner would stop and hurl a stone at Kraag. One man was as inaccurate as the other. Jonner's stones went wide at that distance, and Kraag obviously had not hit Jonner with a bullet.

At last Jonner stopped. He seemed to be fiddling with something that was right on the ground, below Kraag's line of vision. Then a tremendous stone, bigger than Kraag's head, came hurtling toward the sphere. Kraag ducked instinctively, but the missile passed 10 feet above him, still going well.

"What in the devil!" exclaimed Kraag.

"A little innovation of mine, to make things more interesting," said Jonner. "In case you ever want to use the idea, I made me a super-slingshot out of two of the jeep inner tubes from the cargo, and a couple of crowbars I could drive into crevices. Fixed it up yesterday for bombardment purposes."

The duel went on.

There came the time when the hammer of the pistol clicked on an empty chamber.

"How do you refuel this thing, Jonner?" asked Kraag pleasantly. The sun was still high. He could retreat to the interior of the sphere and figure it out if he had to.

"It's pretty hard to do with spacesuit hooks," replied Jonner. "Be glad to demonstrate, if you'll toss me the gun."

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