“But how can you tell when it is properly set,” I asked.

“Put it on, and I’ll show you,” the earthman from Neptune replied. I did so, the flexible band encircled my forehead, with the knob in front, the electrodes in the rear.

“Now turn the micrometer screw until you notice something unusual.”

My clumsy fingers found the little mechanism, twisted it slowly. Nothing happened. I was beginning to fear it was some Neptunian jest, when suddenly my usually halting thought processes clarified. Instead of vague chaotic tags and shreds of thought flitting through my mind, consecutive ideas came to me, clear cut, sharp edged, crystalline.

I stopped short with an exclamation of surprise. Never before had I felt my brain so keen, so brilliant.

“Ah, I can see you have found the proper vibration series,” said Arkon, who had heen watching me closely.

“What is it, how did you know when to stop?” clamored Sid, bursting with curiosity.

I described my sensations, Arkon nodding his head the while. “That is so. Your thought vibrations are now completely shielded from the fest of the world, you see, by forming a wall of neutralization, the waves of thought pressing behind are thrown back upon themselves, and they reinforce and amplify so that the sensations, the ideas they represent, are made more vigorous, more intense.”

“There is only one thought-shield,” came the grave voice of Arkon.

“Then I’m elected,” said Sid, and he tried to grab the circlet off my head. I ducked just in time.