letter or figure is indicated where the fly stops. The most sphinx-like problem ever presented to the public for solution was the second-sight mystery. There have been many exposés of “mental magic,” and some of the best of them are described in “Magic: Stage Illusions and Scientific Diversions, Including Trick Photography.” We have now to concern ourselves with “mental magic” where the results are obtained by clever tricks. There have appeared, from time to time, before the public, individuals who generally work in couples, termed “operators” and “subjects,” who have given performances which were termed mental wonders, silent second-sight, etc. The operator invariably tries to impose on the public with the idea that he possesses some mysterious power over the “subject” by which he is enabled to communicate information to her by his will power over her mind, without a word being spoken. There are, of course, various methods of performing this trick, as by a code of predetermined signals in which sentences like the following are used: “Say the number. Well? Speak out. Say what it is.” But these methods are not comparable with the mechanical means which we are about to describe. The “operator,” after informing the audience of the wonderful powers of divination which the subject possesses, introduces the “subject,” who is invariably a lady. She is seated on a chair near the front of the stage, in plain view of the audience. Her eyes are heavily bandaged, so she cannot see. A committee is invited to go upon the stage to see that the lady has had her eyes properly blindfolded, and also, ostensibly, to help the operator. A large blackboard is placed at one side of the stage, behind the lady. One of the committee is requested to step to this blackboard and write on it, with chalk, some figures, usually up to four or more decimal places; and after he has done so he resumes his seat. The lady immediately appears to add up the number mentally, calling out the numbers and giving the results of the addition. Each member of the committee is invited to step to the blackboard and touch a figure. No sooner has he done so than the lady calls out the number. Other tests of a similar nature are given, such as the extraction of square and cube root, etc. They all prove that the lady has a thorough knowledge of the numbers on the blackboard and the relative position which they occupy. It is, of course, proved beyond a doubt that the lady cannot see the blackboard. The question then arises, How does she obtain the information? There are two methods of performing this trick. In either case her information is obtained from a confederate, who is generally concealed under the stage, who has the blackboard in sight, and who transmits to the lady the desired information. [Illustration: Fig. 23.--The Foot Telegraph.]