Suddenly one of the beasts approached them with a leap. There were two big eyes and two rows of teeth that came together with a snap, right on Phil's trouser-leg. He jerked himself away, sacrificing some square inches of trouser-leg, and, whirling around, kicked at the thing with all his force. It almost paralyzed his foot, for the animal seemed to be made of wood or bone. But it disappeared, and, as it did, both of them felt a queer, nauseating jolt. A few more minutes' walk brought them back to the safe without seeing any more s.p.a.ces; and the sight of its black iron bulk filled them with a home-like relief, which in a moment they recognized as a mockery.

"Are we on a sphere of some sort?" Phil asked.

"Probably on an irregular ma.s.s of matter," Ione replied, "part of which is Tony's concrete floor, and part of which comes out of some other dimension. This ma.s.s of matter is at one end of a long, bar-like portion of s.p.a.ce, the middle of which is pivoted in our world, somewhere in Chicago, and both ends of which are free in hypers.p.a.ce."

"Then," suggested Phil, "why can't we walk down to the axle on which it is balanced, and step out into Chicago?"

"Because there isn't any _matter_ for us to walk on. We are not able to move about in s.p.a.ce, in three dimensions, you know. We can only get around in two dimensions, on the surface of _matter_."

"Well, let's try another exploration trip at right angles to our first one. After all, these 's.p.a.ces' are an interesting show, and I want to see some more."

They started out in the selected direction, and after a short walk got a glimpse of a vast s.p.a.ce dotted with stars and nebulae, with two bright moons sailing overhead. A few steps farther on was a wall of solid granite, near enough to touch with their hands. Again, there was an intensely active ma.s.s of weaving bright stripes and loops and circles, seeming to consist of light only, and making them dizzy in a few seconds. Ione wondered if it might not be something like an organic molecule on a large scale. Again, odd, queer, indescribable shapes and outlines would appear and disappear, obviously three-dimensional sections of multi-dimensional things, cut by s.p.a.ce.

Once they pa.s.sed a place of intense cold and terrific noise and escaped destruction or lunacy only because it took them the merest instant to get past.

They arrived back at the safe, very much fatigued from the strain, their minds woefully confused. Hunger and thirst were beginning to thrust up their little reminders; and for the first time the terrors of their position, flung out into hypers.p.a.ce on a small, barren piece of matter, began to seem real.

After a rest they started out again. As Phil had touched, in kicking it, a creature from another "s.p.a.ce," perhaps they might find water and even food somewhere. They retraced their first steps to the spot where they had at first seen water. They found it again and were able to dip their hands into it. It was warm, and too salty to drink. They came to the place with the creepers or vines, and Phil reached out and seized one of them. It was heavy, rubbery, and elastic, stretching readily as he pulled it.

"These little lurches that we feel must be the snapping back of the s.p.a.ce-puckers as expressed by tensors," Ione remarked. "Every time matter goes in or out of s.p.a.ce, the nature of s.p.a.ce is altered."

"Well," observed Phil, releasing the vine, "I'd better be careful. If one of these things hauls me off here, our last bond with home is gone. I don't want to get lost in some other s.p.a.ce."

As he released the vines they snapped back to their places, and the forest of them dimmed a little and reappeared.

They made the round again, dodging cautiously past the point where they had previously found the "Tinkertoy" animals, and succeeded in getting past their snapping teeth. But no promise of food or water did they find anywhere.

"Looks like we're sunk," observed Phil, as they dropped down on the concrete to rest, leaning their backs against the safe.

How time counted in hypers.p.a.ce, neither Phil nor Ione could tell; Phil knew that his watch was running. He knew that it was ages and ages that he sat with his back against the safe, reviewing all the events of his put life, and thinking of this ignominious end to a lively career! He swore half aloud; then suddenly looked at Ione, ready to apologize. He found her weeping silently.

"I should never have let you come into the building with me," he stammered in confusion at her tears.

"Oh, what do I care what becomes of _me_!" she exclaimed angrily. "But who will take care of poor daddy? He doesn't even know when it's time to eat." And she burst into a fresh fit of weeping.

Phil bent his head in the dumbness of profound despair.

PART V

_The Reversible Equation_

Despair, however, is a luxury. Necessity is a stimulus. With the parchings of thirst and the gnawings of hunger, the two young people ceased swearing and weeping. Phil got up and paced about and sat down again. Ione's tears stopped and dried, and she sat and thought.

In the back of her mind there had been forming a vague sort of an idea, which had signalled ahead of itself that there was hope. She sat there and desperately drove her reason to its utmost efforts, to find that idea and bring it to the surface of consciousness. Hand to hand fights with wild animals, battles between ships of the line, vicious duels between ace-aviators in the clouds are tense fights; but they cannot compare in anxious difficulty with the struggle to bring up an unformed idea out of the subconscious mind--especially when one knows that the idea is there, and that it must be found to save one's life.

"Ione!" exclaimed Phil. It was the first time he had used the name.

"What is the matter? You are as tense as a--"

"Ah!" cried Ione, springing up. "Tense! Tensors! I have it!"

Phil gazed at her in alarm. She laughed; at first it was a strained laugh, but gradually it melted into her sunny one.

"No, I'm not crazy. I knew there was a way out, and I've been trying to reason it out. How simple. You remember the little jolts when you pulled at the vines and when you kicked the funny animal? Tensors.

Matter and s.p.a.ce are so closely interrelated that you can't move matter in or out of s.p.a.ce without causing disturbance, recoils, and tremors in s.p.a.ce. Those bits of matter were small, and produced only a slight disturbance. It takes about a hundred pounds of lead to swing this segment--"

"Oho! Got you!" exclaimed Phil. "Not so dumb! The safe!"

"Yes. The safe!" Ione cried.

"Throw it off and watch us swing, eh? What would happen?"

"I might calculate it if I knew the weight of the safe."

"No calculating when I'm around," Phil said. "It couldn't make things any worse. Try it first and calculate afterwards."

They got behind the safe and pushed, and their combined strength against it was about as effective as it would have been in moving the Peoples' Gas Building. They sat down again in despair.

"Suppose we _could_ budge it," Ione said. "All we could do would be to push it around, this piece of matter we are on. That wouldn't help.

We've got to get it out of s.p.a.ce. We can't push it hard enough to do that. It's got to be shot out suddenly--"

"And we haven't got a gun handy," Phil remarked droopingly.

"Not exactly a gun. A sort of sling--"

Phil leaped to his feet.

"A sling. Why! To be sure! The vines!"

Without another word, both of them got up and ran. They hastened in a direction opposite to the one they had at first taken on their trip of exploration, and this brought them first past the "s.p.a.ce" of the Tinkertoy-like animals. As they went by, several of these beasts darted at them, one of them snapping at Ione's heels. She uttered a scream, causing Phil to turn about and kick right and left among them.

He drove them back and escaped from them, rejoining Ione.

"Wait," he said, when they reached the vines. "Remember those wooden b.a.l.l.s. If I could get a few to throw at those critters--"

In a moment they were off, and finally arrived at the point from which they first saw the b.a.l.l.s. Odd it seemed, how they hung suspended in s.p.a.ce, thousands of them, all sizes. Phil reached out and grasped one about the size of a baseball and drew it toward himself. He felt a dizzy lurch and heard Ione scream.

"Let go!" she screamed again.

When he suddenly realized what was going on, he found himself prostrate on the ground, with Ione across him, her arms about his knees.

"Do you realize," she panted, disentangling herself, "that you were pulling yourself out of this s.p.a.ce into that one?"

"Thanks!" said Phil. "Never say die. More careful this time, and a smaller one."