DOUBLE-CUKRENT MAGNETO-FARADIC APPARATUS. 277 



upon the second coil like a copj^er tube, and masked, or neutralised 

 its power ; and that the sudden interruption produced by the in- 

 termissions permitted the physiological action produced by the 

 influence of the current of the secondary coil upon the magnet, to 

 display itself in all its force. If such were the influence exerted 

 by the primary upon the secondary coil in my electro-magnetic 

 instrument, no one could regard it as an induction phenomenon. 

 But it has been shown, by experiment, that this is not the case. I 



thicker and shorter, and the second finer 

 and longer. According to M. Duclienne, 

 the curi'cnt produced in tlie former wire 

 is an induced current of the first order 

 (of the primary coil), and the current jwo- 

 duced in the latter wire is determined 

 by the influence of the former, and is an 

 induced current of the second order (of 

 the secondary coil). M. Duclienne is 

 deceived. The currents produced in the 

 two wires are hotlt under the influence of d 

 maynet which destroys the effect iiroduced 

 bij the first icire upon the second, or rather 

 reduces it to something extremelij smoll. 

 The current produced in the first, and that 

 produced in the second tcire, are both 

 induced currents of the first kind ; only 

 the former, produced in the shorter and 

 thicker loire, is a current of less tension 

 than that produced in the longer and finer 

 wire, and consequently produces less ener- 

 getic effects upon the skin and upon the 

 retina." 



Is there occasion to show the small 

 value of the following experiments, which, 

 according to my opponent, prove iucon- 

 testably the truth of his assertion ? 



I. " Around a fixed magnet," he says, 

 " roll, by snijerposition, two wires of equal 

 diameter and length, and cause the arma- 

 tui"e of the soft iron to act by rotation ; an 

 induced current of the first order will 

 be produced in each wire." 



Yes, if the circuit of the first coil is 

 neither completed nor interrupted by solu- 

 tions of contact produced in its wire by a 

 commutator, as in my double-coil instru- 

 ment ; but then tlie experiment proves 

 nothing against my theory. But if, on 

 the contrary, my learned opponent were 

 placed in the same conchtions that obtain 

 in my magneto-electric instrument, after 

 the explanations of its mechanism and of 

 its action th:it I liave given above, he 

 would doubtless abandon his opinion as 

 untenable. In his experiment, tlien, the 

 current of the second wire evidently 

 receives the influence of the current of the 

 first wire, resulting from the simultaneous 

 action of the magnet, and of the solutions 

 of contact in this wire, as I have already 

 explained. 



ir. After having related the foregoing 

 experiment, M. A. Becquerel adds, " the 

 current of the first wire will be more in- 

 tense than that of the second, the ciurent 

 of the second less intense than that of the 

 j first, by reason of its greater distance 

 j from the magnet. The current of the 

 : second wire will no longer produce the 

 I special efl'ects of the so-called currents of 

 the second kind." 



From the last point of view, this experi- 

 ment proves absolutely nothing, for many 

 reasons : 1. Why change the ordinary 

 conditions of tlie electro-medical instru- 

 ments of which we have to study the 

 special properties? How is that an instru- 

 ment of double induction the wires of 

 which are of equal diameter ? 2. There is 

 no maker of volta-faradic instruments who 

 does not know that one of the principal 

 conditions for obtaining great physio- 

 logical power in the secondary (induced) 

 coil is, tliat its wire should not only be 

 much finer, but also mm^h longer than the 

 inductive wire. For what reason should 

 it not be the same in a double-current 

 magneto-faradic apparatus ? Let us keep 

 to the que.-ition, which is, to determine 

 the properties of the current of the secon- 

 dary Coil, developed in a wire that is fine 

 and long, as compared with the proper- 

 ties of the current of the primary coil 

 (extra cm-rent) produced in a wire that is 

 tliicker and shorter. I have already proved 

 (see Chap. I., Part III., b, page 30), with 

 regard to volta-faradic instruments, that 

 the physiological properties of the same 

 coil of fine wire differ accordingly as its 

 current, in common language, is an in- 

 duced or an extra ciurent. 



It is hard to understand why it should 

 be otherwise with regard to electro-mag- 

 netic instruments ; and I therefore read 

 with much siu-prise the following asser- 

 tion by M. A. Becquerel. " If a fixed 

 magnet be surrounded by only a single 

 wire, very fine, and very long, it will 

 yield a current of great tension, which 

 possesses all the properties of the so-called 

 currents of the second kind." This asser- 

 tion is in direct contradiction to the facts 

 established by my experimental researches. 



