280 LOCALIZED ELECTRIZATION. 



"We may therefore easily understand that the mechanical 

 variation can only give rise to induced currents that are scarcely 

 appreciable when compared with those that are produced by in- 

 terruption of a current by solution of the circuit. 



" If, on the contrary, we place this extra current in relation with 

 the circuit upon which it can act inductively, it will determine 

 the induced current represented in fig. 65. Its negative part is 

 slightly marked, but it is not the same with its positive part, 

 which may possess a greater intensity, and may present a more 

 sudden variation, than the extra current itself, so that it may also 

 differ from the latter in its effects upon the organism. 



" Such a conclusion would be evidently out of the question, if 

 the circuit of the second coil were only subject to the influence 

 of the first. But would it be the same when the second coil, like 

 the first, is in the presence of a magnet, the magnetization of 

 which is determined by the variations of intensity ? 



" We commenced by observing that, as the second coil included 

 in its circuit the human body, the resistance of which is very 

 great, the inductions due to variations of the intensity of the 

 magnet could develop but a feeble current ; and that, moreover, 

 this current not being subject to interruption by the rheotome, 

 there will be in the wire no sensible extra current, so that I cannot 

 see any condition capable of causing an appreciable disturbance in 

 the effects of the induction produced in the second coil by the 

 extra current of the first. 



" Such is, in my judgment, the proper manner of regarding the 

 phenomena exhibited by electro-magnetic instruments; the induc- 

 tive effect of the extra current of the first coil should he the chief 

 cause of that which passes through the second"^ 



B. — The Bheotome. 



In my instrument, by means of a special mechanism, the inter- 

 mission can be obtained either twice or four times for each revolu- 

 tion of the soft iron, according to the indications. In order pro- 

 perly to appreciate the importance of this arrangement, from a 

 practical point of view, it is necessary to recall the theory of those 

 phenomena which are produced in the common magneto-faradic 

 instruments. 



This theory has been stated in the first chapter. It has there 

 been shown : — 1, that two intermissions of the rheotome, for each 

 revolution of the soft iron, produce four inductions, of which two, 

 powerful ones, occur at the moment of the intermissions ; 2, that 



* F. P. Le Eoux, he. cit., p. 36. 



