mind. Frankly, I'd like to know the answer, too."

Ackerman settled for the cyclotron and the temperon. He spent a week of trying, but little came of it, according to him. Barry Ford had come well prepared. The mass spectrograph was a beaut; the cyclotron was a physicist's dream; and the physico-chemical laboratory must have set someone back a cold half billion.

And to top it all, Ackerman had been the mainspring that brought it through, and was now trying to figure out how and why.

He learned more about the nuclear properties of temperon. They were nothing to get excited about, or he considered them normal until the statistician-girl, Joan Laplane looked up from her notes and asked, innocently: "Temperon is stable. The neutron-isotope—making it the next atom-number above, is radioactive. But I note that it is doubly radioactive."

"It is. It either emits an alpha particle and drops two numbers and four masses down, or emits a beta ray and jumps a number up with no change in mass. In the first case the resultant is stable. In the second case, the resultant then emits an alpha particle and an electron and becomes stable—the same element."

"But why should it emit one of two particles?"

"That's a normal state for many radioactives," said Ackerman. "Radioactivity is a sign of atomic instability. The ejection of the unbalancing particle is not instantaneous. It takes 'time'. In the meantime, the nucleus is unbalanced. Now, this unbalance energy is distributed among the particles of the nucleus, and depending whether the alpha collects the necessary energy first or whether the random rambling of this energy drives out a beta ray, we have the splitting of the radioactive ladder. It happens, for instance, in all three of the normal radioactive chains: Thorium, actinium, and uranium. Thorium drops down the scale normally, dropping alpha particles and beta rays until it reaches Thorium C, which is an isotope of bismuth—bismuth 212. There it splits into Thorium C' or Thorium C". Thorium C' emits alpha and becomes lead 208; Thorium C" emits a beta ray and—likewise—becomes lead 208."

"Might it mean an unknown structure of the nucleus?" she asked.

"Might," he said reflectively. "There's isotopes—elements with the same atomic number but different masses. There's isobars—elements with the same atomic masses but different numbers. Maybe there's you-name-it-bars with similar masses and numbers 

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