"I guess you just can't remember." She sighed, baffled.
"It seemed an awful long time to me, waiting out there in the cold, watching the rock while you changed it."
His troubled glance went back to the windless world outside the dome, and something touched his spine with the white chill of the thin light that fell from the far galaxy.
He knew the science of transmutation.
Inspecting industrial atomic piles for the Defense Authority, he had seen awesome demonstrations in which a tiny sample of sodium or aluminum or platinum was cautiously thrust into the hot reactor through an opening in the lead-and-concrete shielding, and came out again as an untouchable mixture of deadly radioactives in which cautious analysis revealed the triumphant traces of man-made magnesium or silicon or gold.
He knew the mechanics of nuclear transformation, by which the savage energies of the pile shattered and rebuilt the atomic units of proton and neutron and electron into different elements.
That was old stuff to him.
But this - this was different!
Cold granite dissolving swiftly to some inexplicable reagent of the mind, to flow into fitted sheets of strongly welded steel thickly backed with insulating fiber-glass, into sealed drums of compressed oxygen complete with pressure gauges and reduction valves, into bright-labeled cans of green beans and that remarkable rhodomagnetic power cell and the slide rule in his trembling hand - matter molded by sheer thought!
He knew no mechanics for that.
The skeptical half of his brain wanted to reject the evidence, but no reluctance to believe diminished the comfortable hard reality of that transparent shell holding back the airless emptiness and the cold. The dome was there, and its solid existence spurred his uncertain search for understanding.
The theory of exchange forces might help again, he thought - that concept of the ceaseless pulsation of identity between one atomic particle and any of its innumerable twins.
Because every particle, conceived as a wave of probability, existed everywhere.
That fact had suggested a provisional answer to the puzzle of teleportation, and now he saw that other equally staggering wonders were also implied - even to the mental creation of this curious refuge.
Because all the chemical and physical properties of matter were determined, obviously, by particular patterns of atomic identity.
Any change of pattern, clearly, would also be a change of property - a transmutation.
And all existing patterns were nothing more than functions of exchange force probability.
Probability!
Itself an unsolved riddle, that must be the answer.
Jane Carter had proved many times that her mind could govern probability, to explode unstable atoms or to change her place in space.
And Lucky Ford had made a simpler demonstration, he recalled, long ago at Dragonrock, with only a pair of dice.
There - somewhere - must lie the truth.
Forester felt reassured by that flicker of understanding - until its brief illumination faded.
For Mark White's unanswered questions came back then to haunt him.
What was the stuff of the mind?
How could it grasp anything, even probability?
What were the laws, and where the limits?
Baffled, he studied the miraculous slide rule in his hand, and nodded with an absent approval.
The sections slid easily, and there were four special scales he recalled once thinking he would like to have for rhodomagnetic problems.
"I suppose I really made it." He put down the rule, turning slowly back to the troubled child. "But still I don't know how."
"You must try to remember," she insisted desperately.
"Please - try awful hard!
The black machines still have Mr. White and the others.
We've just got to help them." "We'll try."
He nodded, his lean jaw set.
Effort furrowed his thin face, but all the escape from Wing IV and the building of the shelter remained darkly mysterious as the dead landscape beneath that leaning arch of frost.
Wearily, he shook his head.
"Can't you think how you learned?" Jane whispered anxiously.
"Can't you remember what you were thinking - just before you forgot?"
"Of course!" He started as it came to him.
"That equation of equivalence."
Why hadn't he thought of that before?
Lying in his cage beneath the machine's suave alertness, he had been excitedly elated with the infinite promise of that final prima materia.
It was far too important, certainly, to be so casually forgotten.
Wondering at the blind spot that had so oddly blotted it out of his mind, he snatched a pencil and hastily set the equation down - taut with a fresh sense of the limitless implications of it, and chilled with curious apprehension that it might somehow slip away again, beyond that inexplicable barrier of oblivion.
"Now?" Jane whispered hopefully.
"Can you remember?"
"Not much." He shook his head, trying not to see the disappointment in her eyes.
"But I think this equation ought to be the key - if I just knew how to use it.
Because it gives the constants of equivalence for ferromagnetic and rhodomagnetic energy, both of them in terms of platinomagnetism - which is also the energy of mind."