"I don't quite mean that," said North. "But what chance there is lies through this apparatus you're looking at now. Sit down; I'll explain while I work. You can help later, when I've explained the machine." He began to tinker amidst the maze of wires. "My discovery of trionite was purely accidental. It was empiric; not based on any theory. There were six or seven chemicals, and I recall the identity of only two of them. The others? Well, count the chemicals in the pharmacopoeia! The only way I could re-discover it would be by accident as I did before--and that would involve too many experiments and too much time. But the formula is buried somewhere in my subconscious mind. I _might_ remember it." Roger Kay eyed the box with some misgivings. "You mean this is--" "The memory of everything we've ever done or seen is latent in our minds--in the molecular structure of the brain. Almost, I might say, in concentric layers. When the present crisis arose, I had been studying the human brain and the nature of thought and memory. Do you follow me?" He looked up from his work and as Roger nodded, he saw how haggard and weary was the face of the elderly scientist. "Consciousness is basically electrical in nature. The act of memory is the shift of that electrical impulse back to a buried stratum of the brain. But the shift is never complete; most of the consciousness stays in the present. We never remember anything perfectly." "Then this machine is to--" "To create a magnetic field of such a nature as to shift the consciousness _as a whole_. By shifting the magnetic field's intensity, I can move back the consciousness, or memory, to complete remembrance of any given moment of the past. In other words, under its influence, I hope to send back my memory to the moment when I jotted down the formula. Earlier or later won't do; I didn't memorize it at any time." His interest completely gripped, Roger Kay stared into the intricate mechanism. "But, sir," he asked, "do you know the exact time that was--down to the minute?" "Fortunately, yes. I recall that it was the day Ann was being given a party for her third birthday. My wife had told me to be home at three o'clock in the afternoon. I was a little late--didn't leave the lab until on the stroke of three, and it was two or three minutes before then that I wrote down the formula." "And you think you can hit that exact moment?" "With a couple of preliminary experiments, yes. If I find that given setting of the dial and the vernier adjustments give me a certain date and time of day, I can calculate the proper adjustment for the time I want." "Amazing!" exclaimed Roger. "Frankly, if it weren't for the wonderful things you've accomplished in other fields, I'd say it was visionary."