That is, you can't start with a gla.s.s of cool water and, hocus-pocus, get it to separate into warm water and ice cube, right?"

"Naturally," I said, "for heaven's sake. I mean that's silly."

"_Very_ silly," he agreed. "You know it yourself, eh? So watch."

He didn't say hocus-pocus. But he did adjust something on one of his gadgets.

There was a faint whine and a gurgling, spluttering sound, like fat sparks climbing between spreading electrodes in a Frankenstein movie.

The water began to steam faintly.

But only at one end! That end was steam; the other was--was--

It was ice. A thin skin formed rapidly, grew thicker; the other open end of the U-tube began to bubble violently. Ice at one end, steam at the other.

Silly?

But I was seeing it!

I must say, however, that at the time I didn't really know that that was all I saw.

The reason for this is that Pudge Detweiler came groaning down the steps to the laboratory just then.

"Ah, Greek," he wheezed. "Ah, Virgie. I wanted to talk to you before I left." He came into the room and, panting, eased himself into a chair, a tired hippopotamus with a hangover.

"What did you want to talk to me about?" Greco demanded.

[Ill.u.s.tration]

"You?" Pudge's glance wandered around the room; it was a look of amused distaste, the look of a grown man observing the smudgy mud play of children. "Oh, not you, Greek. I wanted to talk to Virgie. That sales territory you mentioned, Virgie. I've been thinking. I don't know if you're aware of it, but when my father pa.s.sed away last winter, he left me--well, with certain responsibilities. And it occurred to me that you might be willing to let me invest some of the--"

I didn't even let him finish. I had him out of there so fast, we didn't even have a chance to say good-by to Greco. And all that stuff about demons and hot-and-cold water and so on, it all went out of my head as though it had never been. Old Pudge Detweiler! How was _I_ to know that his father had left him thirty thousand dollars in one attractive lump of cash!

II

Well, there were business reverses. Due to the reverses, I was forced to miss the next few reunions. But I had a lot of time to think and study, in between times at the farm and the shop where we stamped out license plates for the state.

When I got out, I began looking for El Greco.

I spent six months at it, and I didn't have any luck at all. El Greco had moved his laboratory and left no forwarding address.

But I wanted to find him. I wanted it so badly, I could taste it, because I had begun to have some idea of what he was talking about, and so I kept on looking.

I never did find him, though. He found me.

He came walking in on me in a shabby little hotel room, and I hardly recognized him, he looked so prosperous and healthy.

"You're looking just great, Greek," I said enthusiastically, seeing it was true. The years hadn't added a pound or a wrinkle--just the reverse, in fact.

"You're not looking so bad yourself," he said, and gazed at me sharply. "Especially for a man not long out of prison."

"Oh." I cleared my throat. "You know about that."

"I heard that Pudge Detweiler prosecuted."

"I see." I got up and began uncluttering a chair. "Well," I said, "it's certainly good to--How did you find me?"

"Detectives. Money buys a lot of help. I've got a lot of money."

"Oh." I cleared my throat again.

Greco looked at me, nodding thoughtfully to himself. There was one good thing; maybe he knew about my trouble with Pudge, but he also had gone out of his way to find me. So _he_ wanted something out of _me_.

He said suddenly, "Virgie, you were a d.a.m.ned fool."

"I was," I admitted honestly. "Worse than you know. But I am no longer. Greek, old boy, all this stuff you told me about those demons got me interested. I had plenty of time for reading in prison. You won't find me as ignorant as I was the last time we talked."

He laughed sourly. "That's a hot one. Four years of college leave you as ignorant as the day you went in, but a couple 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 d.a.m.n near anything."

"d.a.m.n 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 rehea.r.s.ed 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.