kick backwards, then a shove at the safe. Each time the safe moved. The sight of its movement revived Ione, so that she was able to push also. Gradually it acquired a steady motion, pulled by the contraction of the vines; its progress soon became faster and faster. Phil was about to follow it and give it another push, when Ione drew him back.

Suddenly they experienced a sinking sensation and a fearful vertigo. The snapping animals faded. Ahead of them was the forest of vines, and they saw the safe hurled into it, crashing, plunging into the tangled mass. The whole view crumpled and moved upwards like a swirl of leaves in a wind, and then vanished with a snap.

They were sick and dizzy, but tremendously curious to see everything. The water, the cubistic cliffs, the vast space full of balls, all curiously blurred, appeared in succession. There were blank spaces and then blurred sights of things which they did not recognize, never having seen them before. Then the dizziness and the nausea abated, and ahead of them was a vast yellow blue, a huge nebula, and in it were double-colored suns and ringed planets with swarms of moons; this glorious sight remained for many seconds, as they gazed at it in panting astonishment, half reclining on the concrete; and then it faded. Again the nausea came on; again the succession of blurred views. Eventually the myriad spheres, the water with the leviathans, the forest of vines, each succeeding scene grew more blurred. Their nausea was correspondingly increased, till they were forced to lie down on the ground from illness.

When their giddiness abated, there were blurring views again. There was an impression as though the speed of a train were decreasing as one looks out of the window. And how one view held for several seconds, a vast and wild mountain-range with glaciers and snow peaks by moonlight. When this faded gradually, the scenes began to flick by, more and more rapidly, and grew blurred. Phil and Ione were attacked by nausea until, again, they had to lie down. After that came the familiar succession: the wooden animals, the tangle of vines, the vast sea, the spheres, and more blurred scenes. Then came a pause, with the nebula and the glorious suns swinging into view once again.

"Oh, I understand!" Ione exclaimed; "We're swinging. The safe was so heavy that we swung too violently, too far, and back again—"

"And we keep going till it knocks us out, or till the old cat dies," added Phil.

However, they found that after a number of repetitions of the same program, their giddiness was becoming less; and instead of lying down in the middle of the swing, they could look about. Then it occurred to Phil to time the interval between the nebula and the mountain-range. When the exact halfway point was determined, and after several more swings, they could see dimly the windows and machinery of Tony's laboratory flash by when they passed the middle.

"I don't mean to be a crepe-hanger, but how do you know we will stop at the right point?" Phil asked.

"I don't," replied Ione cheerfully. "But mathematics says so. A freely oscillating segment of space would naturally come to equilibrium in a position parallel to the rest of its own space, would it not?"

There came a swing when they did not reach the nebula on the one hand and the mountain-range on the other. After that, views dropped off from either end of the swing quite rapidly, and before many minutes, they looked into Tony's laboratory a large portion of the time. For many seconds the laboratory held; then it would gradually fade, and reappear again, only to fade into empty nothingness all around.

"The old cat's dead," Phil finally announced.

They sat and stared about them as the laboratory held steady and no further intervening periods of blankness intervened. They both sighed deeply and slumped over on the ground to rest.

"Bang! bang! bang!"

Some sort of hammering woke them up. They looked about them in a daze. It was broad daylight, and things looked queer in the laboratory. There was a smell of scorched rubber and hot oil. Great loops of wire sagged down from above. Several nondescript heaps stood about that might once have been machinery, but now suggested melting snow-men, all fused into heaps. At a table sprawled a queer, misshapen figure that suggested human origin. Both of its hands were burned to cinders to the elbows. Great holes were scorched into the clothes. But the face was recognizable. Tony's playthings had got him at last.

"Looks like something's happened in here!" Phil gasped, in amazement.

"I'll bet it has, too," Ione exclaimed. "This is the first time it occurred to me that our recoil from throwing the safe overboard and the oscillation of our space-segment must have created a tremendous electrical field in the tetra-ordinate apparatus. The reaction is reversible, you see. The field swings the space-segment, or the swinging of the space-segment creates the field. And the field was too much for Tony."

At this point the door fell under the blows of the police, and the raiding squad rushed into the room.