"Finally comes the Holden Machine. The helmet makes contact with the skull in those spots where the probes of the encephalograph are placed. When the brain is stimulated into thought, the brain waves are monitored and recorded, amplified, and then fed back to the same brain-spots. Not once, but multifold, like the vibration of a reed or violin string. The circuit that accepts signals, amplifies them, returns them to the same set of terminals, and causes them to be repeated several hundred times per millisecond without actually ringing or oscillating is the real research secret of the machine. My father's secret and now mine." "And how do we use it?" "You want to memorize a list of ingredients," said James. "So you will put this helmet on your head with the cookbook in your hands. You will turn on the machine when you have read the part you want to memorize just to be sure of your material. Then, with the machine running, you carefully read aloud the passage from your book. The vibrating amplifier in the machine monitors and records each electrical impulse, then furnishes it back to your brain as a successive series of repetitious vibrations, each identical in shape and magnitude, just as if you had actually read and re-read that list of stuff time and again." "And then I'll know it cold?" James shook his head. "Then you'll be about as confused as you've ever been. For several hours, none of it will make sense. You'll be thinking things like a 'cup of salt and a pinch of water,' or maybe, 'sugar three of mustard and two spoonthree teas.' And then in a few hours all of this mish-mash will settle itself down into the proper serial arrangement; it will fit the rest of your brain-memory-pattern comfortably." "Why?" "I don't know. It has something to do with the same effect one gets out of studying. On Tuesday one can read a page of textbook and not grasp a word of it. Successive readings help only a little. Then in about a week it all becomes quite clear, just as if the brain had sorted it and filed it logically among the other bits of information. Well, what about that cookbook?" "Yes," said Mrs. Bagley, with the air of someone agreeing to have a tooth pulled when it hasn't really started to hurt, "I'll get it." * * * * *