years of jail make
you an educated man."

"Also a reformed one."

He said mildly, "Not too reformed, I hope."

"Crime doesn't pay--except when it's within the law. That's the chief
thing I learned."

"Even then it doesn't pay," he said moodily. "Except in money, of
course. But what's the use of money?"

* * * * *

There wasn't anything to say to _that_. I said, probing delicately, "I
figured you were loaded. If you can use your demons to separate U-235
from U-238, you can use them for separating gold from sea water. You
can use them for damn near anything."

"Damn near," he concurred. "Virgie, you may be of some help to me.
Obviously you've been reading up on Maxwell."

"Obviously."

It was the simple truth. I had got a lot of use out of the prison
library--even to the point of learning all there was to learn about
Clerk Maxwell, one of the greatest of physicists, and his little
demons. I had rehearsed it thoroughly for El Greco.

"Suppose," I said, "that you had a little compartment inside a pipe of
flowing gas or liquid. That's what Maxwell said. Suppose the
compartment had a little door that allowed molecules to enter or
leave. You station a demon--that's what Maxie called them himself--at
the door. The demon sees a hot molecule coming, he opens the door. He
sees a cold one, he closes it. By and by, just like that, all the hot
molecules are on one side of the door, all the cold ones--the slow
ones, that is--on the other. Steam on one side, ice on the other,
that's what it comes down to."

"That was what you saw with your own eyes," Theobald Greco reminded
me.

"I admit it," I said. "And I admit I didn't understand. But I do now."

I understood plenty. Separate isotopes--separate elements, for that
matter. Let your demon open the door to platinum, close it to lead. He
could make you rich in no time.

He had, in fact, done just that for Greco.

* * * * *

Greco said, "Here. First installment." He pulled something out of his
pocket and handed it to me. It was metallic--about the size of a
penny slot-machine bar of chocolate, if you remember back that far. It
gleamed and it glittered. And it was ruddy yellow in color.

"What's that?" I asked.

"Gold," he said. "Keep it, Virgie. It came out of sea water, like you
said. Call it the down payment on your salary."

I hefted it. I bit it. I said, "By the way, speaking of salary...."

"Wha