When some years ago, the American public was confronted with the striking exhibitions of muscle-reading, the wildest speculations were indulged in regarding its true _modus operandi_; and the suggestion that all that was done was explicable by the skillful interpretation of the unconscious indications given by the subjects, was scouted or even ridiculed. It was not supposed that such indications were sufficiently definite for the purposes of the "mind-reader," or were obtainable under the conditions of his tests. Again, it was urged that this explanation was hardly applicable to certain striking performances, which in reality involved other and subtler modes of thought-interpretation, and the accounts of which were also exaggerated and distorted. And furthermore, it was argued, too many worthy and learned persons were absolutely certain that they had given no indications whatever. For a time the view that mind-reading was muscle-reading rested upon rather indirect evidence, and upon a form of argument that carries more weight with those familiar with the nature of scientific problems than with the public at large. But the development of experimental research in the domain of psychology has made possible a variety of demonstrations of the truth and adequacy of this explanation. It was with the purpose of securing a visible record of certain types of involuntary movements, that the investigation, the results of which are here presented, was undertaken. [Illustration: FIG. 1.--THE AUTOMATOGRAPH. When in use a screen (not shown in the illustration) cuts off the view of the apparatus from the subject. The recording device, which may also be used separately, is shown in outline in half its full size. R is a glass rod which moves freely up and down in the glass tube T, which is set into the cork C. A rubber band B is provided to prevent the rod from falling through the tube, when not resting upon the recording-plate.]