They disappeared, and the four inspected the place.  As in the other house they had entered, the room was provided with a double row of small windows; some being down near the floor and the others level with the eyes.  These, in addition to two doors, all of which were of translucent material.

On low benches about the room were a number of instruments, some of which looked familiar to the doctor.  He said he had seen something much like them in psychology class, during his college days.  For the most part, their appearance defied ordinary description. [Footnote:  Physicians, biologists, and others interested in matters of this nature will find the above fully treated in Dr. Kinney’s reports to the A. M. A.]

But one piece of apparatus was given such prominence that it is worth detailing.  It consisted of a hollow, cube-shaped metal framework; about a foot in either direction, upon which was mounted about forty long thumb-screws, all pointing toward the inside of the frame.  The inner ends of the screws were provided with small silver pads; while the outer ends were so connected, each with a tiny dial, as to register the amount of motion of the screw.  Smith turned one of them in and out, and said it reminded him of a micrometer gage.

Then Billie noted that the entire device was so placed upon the bench as to set directly over a hole, about ten inches in diameter.  And under the bench was one of the saddlelike chairs.  The architect’s antiquarian lore came back to her with a rush, and she remembered something she had seen in a museum—­a relic of the inquisition.

“Good Heavens!” she whispered.  “What is this—­an instrument of torture?”

It certainly looked mightily like one of the head-crushing devices Billie had seen.  Thumb-screws and all, this appeared to be only a very elaborate “persuader,” for use upon those who must be made to talk.

But the doctor was thinking hard.  A big light flashed into his eyes.  “This,” he declared, positively, “is something that will become a matter of course in our own educational system, as soon as the science of phrenology is better understood.”  And next second he had ducked under the bench, and thrust his head through the round hole, so that his skull was brought into contact with some of those padded thumb-screws.

“Get the idea?” he finished.  “It’s a cranium-meter!”

It did not take Smith long to reach the next conclusion.  “Then,” said he, “our friend Estra is connected with their school system.  Can’t say what he would be called, but I should say his function is to measure the capacity of students for various kinds of knowledge, in order that their education may be adapted accordingly.

“Might call him a brain-surveyor,” he concluded.

“Or a noodle-smith,” added the geologist, deprecatingly.

“Rather, a career-appraiser!” indignantly, from Billie.  “People look to him to suggest what they should take up, and what they should leave alone.  Why, he’s one of the most important men on this whole planet!”