its half-pair equivalent of hard gamma, when the radiation is focussed once more, the radiation produces an iron nucleus."

"I'm still behind, but I probably never will catch up."

"Oh, there's a lot more to it than that," smiled Peter. "Mine is about as simple and incomplete an explanation as you'll ever hear about anything. Most of it is oversimplified to the point of being almost incorrect, but to really explain takes knowledge of matrix mathematics and the theory of nuclear determinants."

"Don't bother. Just go on."

Peter nodded. "The big problem," he said slowly, "was the development of a scanning device. In order to reconstruct any object faithfully, the reformed atom must reassemble in exactly the same relative position. No one could ever do it mechanically. But a magnetic field can bend the radiation if the field is strong and localized. The trouble was in control. The atomic proportions are so minute that the matter of a few micro-micro-amperes will cause success or failure. Considering that the electromagnets carry several hundred amperes, the variation of ten to the minus twelfth amperes is well-nigh impossible to control. It took me five years, but now I've done it."

"And tomorrow?" asked Norma. "Tomorrow you are going to demonstrate this to father."

"Uh-huh."

"And then the next day—?"

Peter Mansfield turned back to the girl with a strained smile. He reached for her and she came into his arms with a smile that matched his. "I'll bet you haven't heard a word I said."

"Yes I did. Most of it went over my head, but at least you've gotten it out of your system. Now, Peter, take me dancing."

"I can't afford to."

"I can. And I'll pout and be disagreeable if you don't let me."

"Damn all headstrong women," grunted Peter. But he went, and after an hour or so he relaxed.

II

They came in a body at nine-thirty the next morning. Peter showed them to chairs in the laboratory, but Walter Higgins remained standing. "These are some of my Board of Directors," he said to Peter. "Meet Mr. Harrison, Vice-President in charge of Engineering and Research of Higgins Development Company. And this is Mr. 

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