There are but six syllables in the Mercurial language, each syllable being represented by a corresponding key. The way these syllables were fingered gave the words. As they could be combined and repeated and combined again, the vocabulary of the boxes was practically unlimited. The syllable notes were of resonant quality and of such divergent timber as to be quickly and easily recognized. The syllable for Key 1 was synonymous with our personal pronoun "I," and was the most assertive and determined note in the whole gamut of the box. The seventh key emitted a sound so utterly unlike the other sounds as to be in a class by itself. It was used for spacing between words, for exclamatory purposes and for the audible expression of laughter and grief. It was likewise the expletive or swear-key; for these small egotists had all the passions of other mortals, and Key 7 acted as a sort of safety valve. The manner in which the key was used gave it its versatility. Day by day our lessons proceeded, the professor learning with a rapidity that was marvelous. He was well along in the polysyllables while I was struggling with the basic tones and acquiring some facility in spacing and in the expression of the feelings. Our ears kept pace with our fingers, and in a fortnight the professor was so eloquent with his word-box that he could now and then play off a metaphor, or some other frill, to the great delight of himself and his auditors. Next to a wonderful jimmy invented by a cracksman named "Cricket" Doniphan, whom I knew well, and who, at that period, was doing time in Stillwater, I take off my hat to that Mercurial word-box as the most marvelous contrivance ever evolved by a thinking mind. I have a very good memory, and when sufficiently proficient with the keys I practiced by repeating passages from "Forty Ways of Cracking Safes," which, as distinguished from "The Sandbagger’s Manual," I considered my _chef d’oeuvre_. I could not discover that my terse English, faulty enough though it was, lost anything in force from translation into the Mercurial tongue. (The word "tongue" is used with reservations, for, of course, tongue that language was not.) Difficulty was experienced in getting a suitable Mercurial equivalent for the good English word "cracksman." Finally, however, I hit upon three quick touches of the swear-key, which made the word intelligible in my own ears if not to any one’s else. Soon I began to observe a little throng gathering across my side of the prison ring, listening intently as I practiced. From day to day the throng increased. Over on the other side of the ring Professor Quinn was absorbed in cutting all manner of scientific capers with his word-box. "The Mutability of Newtonian Law" formed his staple theme, and he was able to put it through the keys with amazing variations.