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THE POPULAR SCIENCE MONTHLY 



desirable that tins confidence should be accompanied by an under- 

 standing of the conditions under which the evidence is presum- 

 ably 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 pro- 

 cesses. When, some years ago, the American public was con- 

 fronted with the striking phenomena of muscle-reading, the wild- 

 est speculations were indulged in regarding its true modi^s 

 operayidi ; and the suggestion that it was due to unconscious indi- 

 cations 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 ac- 

 counts, and that so many worthy and learned persons were abso- 

 lutely 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 



The Automatograpr. — Wlieu 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 



