i68 THE POPULAR SCIENCE MONTHLY. 



back to a very remote date) has been appealed to for answers to ques- 

 tions of very diverse character. 



When, however, "Odyle" came to the front, and the world of 

 curious but unscientific inquirers was again "possessed" by the idea 

 of an unknown and mysterious agency, capable of manifesting itself 

 in an unlimited variety of ways, the j)e9idnle explorateur was brought 

 into vogue, under the name of odometer^ by Dr. Herbert Mayo,* who 

 investigated its action with a great show of scientific precision ; start- 

 ing, however with the foregone conclusion that its osciHations were 

 directed by tlie hypothetical " odyle," and altogether ignoring the 

 mental participation of the operator, whom he supposed to be as pas- 

 sive as a thermometer or a balance. By a series of elaborate experi- 

 ments, he convinced himself that the direction and extent of the 

 oscillations could be altered, either by a change in the nature of the 

 substances placed beneath the " odometer," or by the contact of the 

 hand of a person of the opposite sex, or even of the experimenter's 

 other hand, with that from which it was suspended. And he grad- 

 ually reduced his result to a series of definite laws, which he re- 

 garded as having the same constancy as those of physics or chemis- 

 try. Unfortunately, however, other experimenters, who worked out 

 the inquiry with similar perseverance and good faith, arrived at such 

 different results, that it soon came to be obvious that what astro- 

 nomical observers call the "personal equation" of the individual has 

 a very large share in detei'miniiig them. A very intelligent medical 

 friend of my own, then residing abroad, wrote me long letters full of 

 the detailed results of his own inquiries, on which he was anxious for 

 my opinion. My reply was simply : " Shut your eyes, or turn them 

 away, and let some one else watch the oscillations under tlie condi- 

 tions you have specified, and record their results ; you will find, if I 

 do not mistake, that they will then show an entire v:ant of the con- 

 stancy you have hitherto observed." His next letter informed me 

 that such proved to be the case; so that he had come entirely to 

 agree with me as to the dependence of the previous uniformity of his 

 results on his own expectancy. 



A curious variation of the " odometer " was introduced by Mr. 

 Rutter, the manager of the gas-works at Brighton, under the name 

 of " magnetometer," which was simply a gallows-shaped frame, 

 mounted on a solid base, having a metallic ball suspended from its 

 free extremity. When the finger was kept for a short time in contact 

 with this frame, the ball began to oscillate, usually in some definite 

 direction, changing that direction with any change of circumstances, 

 after the manner of Dr. Mayo's " odometer." To many persons, as 

 to Mr. Kutter himself, it appeared impossible that these oscillations 

 could have their origin in any movement of the operator ; but every 

 one who knows how difficult it is to prevent vibrations in the sup- 

 1 "The Truths contained in Popular Superstitions," 1851. 



