"I'm way ahead of you," I said. "But that wouldn't work. All your
kinetic energy would go right back to heat, on impact--and eventually
that little ball would build up enough speed to blast its way through
any box you could build."

"Then how would you work it?"

"Well," I said, choking down the rest of my rum, "you'd seal the ball
in a big steel cylinder, attach the cylinder to a crankshaft and
flywheel, give the thing a shake to start the ball bouncing back and
forth, and let it run like a gasoline engine or something. It would
get all the heat it needed from the air in a normal room. Mount the
apparatus in your house and it would pump your water, operate a
generator and keep you cool at the same time!"

I sat down again, shakily, and began pouring myself another drink.

Farnsworth had taken the ball from me and was carefully putting it
back in its padded box. He was visibly showing excitement, too; I
could see that his cheeks were ruddier and his eyes even brighter than
normal. "But what if you want the cooling and don't have any work to
be done?"

"Simple," I said. "You just let the machine turn a flywheel or lift
weights and drop them, or something like that, outside your house. You
have an air intake inside. And if, in the winter, you don't want to
lose heat, you just mount the thing in an outside building, attach it
to your generator and use the power to do whatever you want--heat your
house, say. There's plenty of heat in the outside air even in
December."

"John," said Farnsworth, "you are very ingenious. It might work."

"Of course it'll work." Pictures were beginning to light up in my
head. "And don't you realize that this is the answer to the solar
power problem? Why, mirrors and selenium are, at best, ten per cent
efficient! Think of big pumping stations on the Sahara! All that heat,
all that need for power, for irrigation!" I paused a moment for
effect. "Farnsworth, this can change the very shape of the Earth!"

Farnsworth seemed to be lost in thought. Finally he looked at me
strangely and said, "Perhaps we had better try to build a model."

* * * * *

I was so excited by the thing that I couldn't sleep that night. I kept
dreaming of power stations, ocean liners, even automobiles, being
operated by balls bouncing back and forth in cylinders.

I even worked out a spaceship in my mind, a bullet-shaped affair with
a huge rubber ball on its end, gyroscopes to keep it