Page:Popular Science Monthly Volume 40.djvu/766

744 desirable that tins confidence should be accompanied by an understanding of the conditions under which the evidence is presumably valid and when likely to mislead. Sense deceptions, faulty observation, exaggeration, neglect, fallacy, illusion, and error abound on all sides and emphasize the need of a calm judgment, a well-equipped intellect, a freedom from haste and prejudice, an appreciation of details and nice distinctions, in the determination of truth and the maintenance of mental health.

For these and other reasons it is important to demonstrate experimentally the readiness with which normal individuals may be made to yield evidence of unconscious and involuntary processes. When, some years ago, the American public was confronted with the striking phenomena of muscle-reading, the wildest speculations were indulged in regarding its true modus operandi; and the suggestion that it was due to unconscious indications skillfully interpreted was ridiculed, mainly for the reasons that this explanation was hardly applicable to certain extreme instances involving considerable good fortune, other and subtler modes of interpretation, as well as some exaggeration in the accounts, and that so 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 modes of reasoning that do not

 —When in use a screen is interposed concealing the apparatus from the subject. There is also a sheet of paper on the upper glass plate, which has been removed to show the glass balls.

carry great conviction to the ordinary mind. To supplement this evidence by a clear exposition of the naturalness and regularity of these involuntary movements is our present task.

Inasmuch as the movements in question are often very slight, delicate apparatus is necessary, the description of which may properly precede an account of the results. There is first a strong