The course of instruction was not particularly difficult to memorize. It seemed that for each color of light behind the ground-glass panels one must thrust a finger into a different one of the holes below; hold it there in spite of the pain, till the colored light went out, and then remove it. The process was very hard on the fingers, made of metal though they were. What was it the farmer had shouted down the hall? "Wears your fingers out?" Well, it did that, all right. After an hour or two of it, when he had learned to perform the various operations with mechanical precision and the tip of his index finger had already begun to scale off, the ape-man smiled at him, waved approval and reaching down beneath the black board, pulled out a drawer from which he extracted a finger-tip, made in the same metal as those he already bore, and proceeded to show Sherman how to attach it. As a mechanic, he watched the process with some interest. The "bone" of the finger, with its joint, screwed cunningly into the bone of the next joint below, the lower end of the screw being curiously cut away and having a tiny point of wire set in it. The muscular bands had loose ends that merely tucked in, but so well were they fashioned, that once in position, it was impossible to pull them out until the finger-tip had been unscrewed. The instruction process over, he was returned to his cell, wondering what was to happen next. The poisoned paradise was becoming less of a paradise. He speculated on the possibility of wrecking the car that bore him from place to place, but finally decided that it could not be done without some heavy tool and was hardly worth the trouble in any case until he was more certain of getting away afterward. CHAPTER XIII The Lassan When the car next called for him, it took a much longer course; one steadily downward and around a good many curves as he could judge from the way in which it swayed and gained and lost speed. It was fully a twenty-minute ride, and when he stepped out it was not into a room of any kind, but in what appeared to be a tunnel cut in the living rock, at least six feet wide and fully twice as high. The rock on all sides had been beautifully smoothed by some unknown hand, except underfoot where it had been left rough enough to give a grip to the feet.