NATURAL PHILOSOPHY. 137 



result occurs with others ; for I have had two boards arranged, separ- 

 ated, not by rollers but by plugs of vulcanized rubber, and with the 

 vertical index : when a person with his hands on the upper board is 

 requested to press only downward, and the index is hidden from his 

 sight, it moves to the right, to the left, to him and from him, and in 

 all horizontal directions : so utterlv unable is he strictlv to fulfil his in- 



V +' 



tention without a visible and correcting indicator. Now, such is the 

 use of the instrument with the horizontal index and rollers : the mind 

 is instructed, and the involuntary or quasi involuntary motion is 

 checked in the commencement, and therefore never rises up to the 

 degree needful to move the table, or even permanently the index it- 

 self. 



The subject of the table movement has been also brought before the 

 French Academy, in a paper by M. Seguin, one of the members. 

 The subject, as might be supposed, found no favor with Arago, who, 

 after the reading of this communication, intimated, in brief but some- 

 what vague terms, that his belief was, that the movement of the 

 tables is caused by muscular action. And he proceeded to say : 

 " What is most extraordinary and most difficult to explain in the phe- 

 nomenon is the circumstance, that with impulsions, so to speak, in- 

 finitely small, imprinted on the table with the fingers, we in time can 

 communicate to it active movements, (ties mouvernens considerables") 

 This, however, he alleged, is no novelty, as " Mr. Elliot, a watchmak- 

 er, relates in the ' Philosopical Transactions ' of some years ago, that 

 two clocks having been hung to a wall, a foot apart, one of which was 

 going, the other standing, the latter after a while began going too, 

 being set in motion by the imperceptible vibrations transmitted from 

 the other through the solid body between them and it even contin- 

 ued going after the first one was stopped." 



INFLUENCE OF THE MIND ON MUSCULAR AND NERVOUS 



ACTION. 



The following letter on the subject of magnetization, &c., was ad- 

 dressed to the illustrious savant, Ampere, by M. Chevreuil, a member 

 of the French Academy, and was first published in the Revue des 

 Deux Mondes, in the year 1833. It was in 1812 that several persons 

 affirmed that a pendulum formed of a heavy body and a flexible 

 string would oscillate when held by the hand over certain substances, 

 although the arm should remain stationary, and they urged M. Chev- 

 reuil to make the experiment. 



" The pendulum I used (says M. Chevreuil) was an iron ring sus- 

 pended by a flaxen thread ; it had been arranged by a person who 

 was very anxious that I should verify for myself the phenomenon 

 which appeared when it was placed over water, a block of metal, or a 

 living being --a phenomenon which I saw appear in his hands. It 

 was not, I confess, without surprise that I saw it reproduced when, 

 having taken hold with my right hand of the pendulum's string, I 

 placed it above the mercury reservoir of my air-pump, an anvil, sev- 



