He got out the flashlight and some paper from his immense pocket and did some figuring. The flashlight was almost unmanageable.

Underneath him the floor became warm. Automatically he shifted, a little up the tube to avoid the heat. “If I stay here long enough,” he murmured, “I might be—”

The tube leaped again, rushing off in all directions. He found himself floundering in a sea of rough fabric, choking and gasping. At last he struggled free.

“One and a half feet,” Grote said, staring around him. “I don’t dare move any more, not at all.”

But when the floor heated under him he moved some more. “Three-quarters of a foot.” Sweat broke out on his face. “Three-quarters of one foot.” He looked down the tube. Far, far down at the end was a spot of light, the photon beam crossing the tube. If he could reach it, if only he could reach it, if only he could reach it!

He meditated over his figures for a time. “Well,” he said at last, “I hope I’m correct. According to my calculations I should reach the beam of light in about nine hours and thirty minutes, if I keep walking steadily.” He took a deep breath and lifted the flashlight to his shoulder.

“However,” he murmured, “I may be rather small by that time…” He started walking, his chin up.

Professor Hardy turned to Pitner. “Tell the class what you saw this morning.”

Everyone turned to look. Pitner swallowed nervously. “Well, I was downstairs in the basement. I was asked in to see the Frog Chamber. By Professor Grote. They were going to start the experiment.”

“What experiment do you refer to?”

“The Zeno one,” he explained nervously. “The frog. He put the frog in tube and closed the door. And then Professor Grote turned on the power.”

“What occurred?”

“The frog started to hop. He got smaller.”

“He got smaller, you say. And then what?”

“He disappeared.”

Professor Hardy sat back in his chair. “The frog did not reach the end of the tube, then?”

“No.”

“That’s all.” There was a murmuring from the class. “So you see, the frog did not reach the end of the tube, as expected by my colleague, Professor Grote. He will never reach the end. Alas, we shall not see the unfortunate frog again.”

There was a general stir. Hardy tapped with his pencil. He lit his pipe and puffed calmly, leaning back in his chair. “This experiment was quite an awakener to poor Grote, I’m afraid. He has had a blow of some unusual proportion. As you may have noticed, he hasn’t appeared for his afternoon classes. Professor Grote, I understand, has decided to go on a long vacation to the mountains. Perhaps after he has had time to rest and enjoy himself, and to forget—”

Grote winced. But he kept on walking. “Don’t get frightened,” he said to himself. “Keep on.”

The tube jumped again. He staggered. The flashlight crashed to the floor and went out. He was alone in the enormous cave, an immense void that seemed to have no end, no end at all.

He kept walking.

After a time he began to get tired again. It was not the first time. “A rest wouldn’t do any harm.” He sat down. The floor was rough under him, rough and uneven. “According to my figures it will be more like two days, or so. Perhaps a little longer…”

He rested, dozing a little. Later on he began to walk again. The sudden jumping of the tube had ceased to frighten him; he had grown accustomed to it. Sooner or later he would reach the photon beam and cut through it. The force field would go off and he would resume his normal size. Grote smiled a little to himself. Wouldn’t Hardy be surprised to—

He stubbed his toe and fell, headlong into the blackness around him. A deep fear ran through him and he began to tremble. He stood up, staring around him.

Which way?

“My God,” he said. He bent down and touched the floor under him. Which way? Time passed. He began to walk slowly, first one way, then another. He could make out nothing, nothing at all.

Then he was running, hurrying through the darkness, this way and that, slipping and falling. All at once he staggered. The familiar sensation: he breathed a sobbing sigh of relief. He was moving in the right direction! He began to run again, calmly, taking deep breaths, his mouth open. Then once more the staggering shudder as he shrank down another notch; but he was going the right way. He ran on and on.

And as he ran the floor became rougher and rougher. Soon he was forced to stop, falling over boulders and rocks. Hadn’t they smoothed the pipe down? What had gone wrong with the sanding, the steel wool—

“Of course,” he murmured. “Even the surface of a razor blade… if one is small…”

He walked ahead, feeling his way along. There was a dim light over everything, rising up from the great stones around him, even from his own body. What was it? He looked at his hands. They glittered in the darkness.

“Heat,” he said. “Of course. Thanks, Hardy.” In the half light he leaped from stone to stone. He was running across an endless plain of rocks and boulders, jumping like a goat, from crag to crag. “Or like a frog,” he said. He jumped on, stopping once in a while for breath. How long would it be? He looked at the size of the great blocks of ore piled up around him. Suddenly a terror rushed through him.

“Maybe I shouldn’t figure it out,” he said. He climbed up the side of one towering cliff and leaped across to the other side. The next gulf was even wider. He barely made it, gasping and struggling to catch hold.

He jumped endlessly, again and again. He forgot how many times.

He stood on the edge of a rock and leaped.

Then he was falling, down, down, into the cleft, into the dim light. There was no bottom. On and on he fell.

Professor Grote closed his eyes. Peace came over him, his tired body relaxed.

“No more jumping,” he said, drifting down, down. “A certain law regarding falling bodies… the smaller the body the less the effect of gravity. No wonder bugs fall so lightly… certain characteristics…”

He closed his eyes and allowed the darkness to take him over, at last.

“And so,” Professor Hardy said, “we can expect to find that this experiment will go down in science as—”

He stopped, frowning. The class was staring towards the door. Some of the students were smiling, and one began to laugh. Hardy turned to see what it; was.

“Shades of Charles Fort,” he said.

A frog came hopping into the room.

Pitner stood up. “Professor,” he said excitedly. “This confirms a theory I’ve worked out. The frog became so reduced in size that he passed through the spaces—”

“What?” Hardy said. “This is another frog.”

“—through the spaces between the molecules which form the floor of the Frog Chamber. The frog would then drift slowly to the floor, since he would be proportionally less affected by the law of acceleration. And leaving the force field, he would regain his original size.”

Pitner beamed down at the frog as the frog slowly made his way across the room.

“Really,” Professor Hardy began. He sat down at his desk weakly. At that moment the bell rang, and the students began to gather their books and papers together. Presently Hardy found himself alone, staring down at the frog. He shook his head. “It can’t be,” he murmured. “The world is full of frogs. It can’t be the same frog.”

A student came up to the desk. “Professor Hardy—”

Hardy looked up.

“Yes? What is it?”

“There’s a man outside in the hall wants to see you. He’s upset. He has a blanket on.”

All right,” Hardy said. He sighed and got to his feet. At the door he paused, taking a deep breath. Then he set his jaw and went out into the hall.

Grote was standing there, wrapped in a red-wool blanket, his face flushed with excitement. Hardy glanced at him apologetically.