And you don't get energy out without putting energy in."

"Oh," he said, "that's the really interesting thing. Of course you're right; energy _does_ go into the ball. Here, I'll show you."

He let the ball drop again and it began bouncing, higher and higher, until it was hitting the ceiling. Farnsworth reached out to catch it, but he fumbled and the thing glanced off his hand, hit the mantelpiece and zipped across the room. It banged into the far wall, richocheted, banked off three other walls, picking up speed all the time.

When it whizzed by me like a rifle bullet, I began to get worried, but it hit against one of the heavy draperies by the window and this damped its motion enough so that it fell to the floor.

* * * * *

It started bouncing again immediately, but Farnsworth scrambled across the room and grabbed it. He was perspiring a little and he began instantly to transfer the ball from one hand to another and back again as if it were hot.

"Here," he said, and handed it to me.

I almost dropped it.

"It's like a ball of ice!" I said. "Have you been keeping it in the refrigerator?"

"No. As a matter of fact, it was at room temperature a few minutes ago."

"Now wait a minute," I said. "I only teach physics in high school, but I know better than that. Moving around in warm air doesn't make anything cold except by evaporation."

"Well, there's your input and output, John," he said. "The ball lost heat and took on motion. Simple conversion."

My jaw must have dropped to my waist. "Do you mean that that little thing is converting heat to kinetic energy?"

"Apparently."

"But that's impossible!"

He was beginning to smile thoughtfully. The ball was not as cold now as it had been and I was holding it in my lap.

"A steam engine does it," he said, "and a steam turbine. Of course, they're not very efficient."

"They work mechanically, too, and only because water expands when it turns to steam."

"This seems to do it differently," he said, sipping thoughtfully at his dark-brown martini. "I don't know exactly how--maybe something piezo-electric about the way its molecules slide about. I ran some tests--measured its impact energy in foot pounds and compared that with the heat loss in BTUs. Seemed to be about 98 per cent efficient, as close as I could tell. Apparently it converts heat into bounce very well. Interesting, isn't it?"

"_Interesting?_" I almost came flying out of my chair. My mind was beginning to spin like crazy. "If you're not pulling my leg with this thing, Farnsworth, you've got something by the tail there that's just a little bit bigger than the discovery of fire."

He blushed modestly. "I'd rather thought that myself," he admitted.

"Good Lord, look at the heat that's available!" I said, getting really excited now.

* * * * *

Farnsworth was still smiling, very pleased with himself. "I suppose you could put this thing in a box, with convection fins, and let it bounce around inside--"

"I'm way ahead of you," I said.