He studied the powder and rubbed a bit between his thumb and forefinger.

He asked, "May I have the bag?"

"Sure," Rick agreed readily. "What is the stuff?"

Baxter took the cement bag and folded it neatly, then he took a plastic bag from his case and put the cement bag inside. "I can't be sure," he said. "About its precise ident.i.ty, I mean. But it seems to be pulverized ore, and my guess would be carnot.i.te. Don't worry about the radioactivity. You could live in a house made of this stuff and it wouldn't be dangerous. The level of activity is very low. I suppose you have no idea where the sample came from?"

Rick shook his head. "Where does carnot.i.te come from, usually?"

"The Colorado Plateau, for the most part. There are other deposits, but none around here. This stuff was almost certainly imported. Have you any idea why?"

"Not the slightest. It's a complete mystery."

Baxter nodded. "Well, that's all I can do for now. I'll a.n.a.lyze the sample and let Steve Ames know exactly what it is, but I'm betting on carnot.i.te. If you find a few hundred tons of it, you can sell it to the Atomic Energy Commission. So long."

The expert tipped his hat to the girls and walked to his car.

"What was that all about?" Barby demanded. "You and Scotty seemed to know what he was talking about, but it was all Greek to Jan and me."

Rick explained on the way back to the farm. "There are four main kinds of radioactivity. They're called alpha, beta, gamma, and neutrons. Our sample has alpha and gamma. That means it doesn't come from either bomb debris or from a reactor, because fission takes place in both, and there is almost always beta activity as well as gamma in the products of fission. But some isotopes of uranium and thorium have little beta, with some alpha and gamma, so Baxter concluded we had powdered uranium ore.

There are many kinds of ore. Pitchblende is the best, but carnot.i.te, which is a gray rock with yellowish streaks, is also good ore. Got it now?"

Jan Miller asked, "How do you know all this, Rick?"

The boy chuckled. "From a.s.sociating with your father and mine, not to mention Weiss, Zircon, and the other scientists. They talk and Scotty and I listen. Also, Dad has a lot of books on atomic energy, and some of them are simple enough for me to read."

The Sky Wagon was over the Miller farm in a very short time, but before landing Rick made a swing of the area. The young people readily identified the mine and picnic grounds, and Rick pointed out the quarry into which he had tumbled.

Scotty said, "Something's been bothering me. If the Frostola man is new in this area, how could he have known the terrain well enough to lead us on that wild-goose chase?"

"He's new, but not that new," Rick pointed out. "He's had weeks in which to study the lay of the land. Besides, he does his haunting at night--if he's the one--and he roams the fields near the mine. He must know his way around."

"You're right," Scotty a.s.sented. "Now tell me this: why did he take the cement bags?"

"To keep us from finding out that they didn't contain cement," Rick said. "It has to be the reason. That means he knew about the bags, and maybe he even buried them. He didn't bury them deep, because who would think anything of a bunch of cement bags, except a pair like us? Then, when he saw they had turned up, he collected them and took them somewhere else. The bags we found this morning may even be the same ones, although I think they're a second set. He'd hide the first set better than he did at first."

"Your language is confused, but I get your meaning." Scotty grinned.

"Okay, detective. Set us down. It's suppertime."

Rick swung into his landing pattern. "Anyway, we've made progress," he commented with satisfaction. "We started with just a ghost. Now look what we've got!"

CHAPTER XI

The Ghost Reappears

Belsely, the tenant farmer, had no difficulty in establishing a connection between Jethro Collins, real-estate agent, and the Frostola man. He made a quick trip to town on the morning following the flight to Falls Church, and reported that the ice-cream vendor was renting a room from Collins.

"No doubt about that connection," was Rick's comment. Then, because they had not talked to Belsely at any length, he questioned the farmer about the appearances of the ghost in the fields nearby.

"I've seen him four or five times, not counting the night you chased him," the farmer said. "Funny thing about the night he got the alarm going on your plane."

"What was funny?" Scotty asked.

"He was alone."

"But he's always alone," Rick exclaimed.

"Nope. He's alone at the mine, but when he walks the fields he has some of his men with him. Sometimes one, sometimes two or three. Only saw him alone that once--the night you chased him."

This was a new angle. Rick and Scotty looked at each other, puzzled.

"You've seen the others?" Scotty asked.

"Sure have. Not close to, you can bet. Got no wish to tangle with spirits, not me. But I saw them. They walked in the cornfield on top of the mine hill, and they walked in the field where your plane is. They was lookin' for somethin'."

"How do you know?" Rick demanded.

"They'd walk, then stop, and bend over. Like they were searchin' the ground. Bet one of 'em lost a head and is huntin' for it."

"Did you see where they came from, or went to?"

"Not me. I got curiosity, but not the kind that killed that cat they tell about. Like I say, me and spirits don't mix, none to speak of."

Rick pondered the information. "Are these ghostly walks at nine o'clock?"

"No. Mostly around midnight."

Rick turned to Scotty. "What do you make of that?"

"Nothing," Scotty replied. "Not a thing. You say you've seen as many as three men plus the Blue Ghost?"

"That's correct. None of them shine like the Blue Ghost himself, though.

Most curious thing I ever saw was the night they pulled a wagon, collectin' the invisible dead from the battlefield."

Rick's hair had an impulse to stand on end. The calm, factual way in which the tenant farmer piled mystery on mystery was incredible.

"You mean you saw ghosts pulling a ghost wagon?" the boy asked incredulously.

"Like I said. More a cart than a wagon, I suppose you'd say. They hauled it back and forth, and the mist trailed out behind it. Once in a while they'd stop and gather and look at the ground. Must be they were searchin' for their dead. Don't know why else they'd need a wagon. And that Blue Thing leadin' the way every time. Up and down, back and forth."

Scotty asked, "Where were you while all this was going on?"

"In the orchard, scared pink, but not so scared as curious."

A man of real courage, Rick thought. Believed in ghosts, but had the nerve to watch them in action. "Mr. Belsely, you said none of them shone like the Blue Ghost. Did the others look solid?"