30 LOCALIZED ELECTRIZATION. 



acutely excited ; the property that I liave made known as being 

 peculiar to tlie current of the second helix. The experiment was 

 tried as follows : — 



Ex23erimeiit. — I mounted the two helices used in the preceding experiment, 

 and made a second fine helix, the same as the former, to cover the helix of 

 larger wire. Into the latter I conducted an intermitting current of the same 

 electro-motor. The force of the current of the second helix, when iiroduced 

 by the induction of the first, was very considerably augmented (as would be 

 foreseen). In order to compare the special properties of this second helix, 

 yielding an induced current, with those of the similar helix, yielding only 

 an extra current, I caused the current of the former to pass through a 

 water regulator, until it was impossible, with the moist hand to distinguish 

 one current from the other. They might therefore be thoiight to be per- 

 fectly equal, with regard to their i:)hysiological action upon the sensibility of 

 the skin. But on limiting their action to the surface of the skin, and test- 

 ing them alternately, the induced current of the fine wire was found to 

 produce much more sensation than the fine-wire extra current. 



We have therefore seen in this experiment, that a helix made 

 of wire 1000 metres in length, and one sixth of a millimetre in 

 diameter, and of which the power, as the source of an extra cur- 

 rent, scarcely equalled that of a helix made from a wire 200 

 metres in length, and one millimetre in diameter, acquired an 

 enormous increase of power, as regards the cutaneous sensibility, 

 when excited by an inductive helix of the thicker and shorter 

 wire. 



It will doubtless have been observed that in the foregoing 

 experiments I refrained from placing the soft iron in the centre 

 of the inductive helix ; that is to say, that magnetism had no 

 influence upon the phenomena of induction that I have described. 

 My experiments were conducted in this manner for the purpose of 

 showing how little foundation there is for the opinions of certain 

 writers, who have ascribed the special action of the current of the 

 second helix to the influence of magnetism. " There is," says 

 M. E. Becquerel, "another observation that should be made. M. 

 Duchenne, by jdacing in his instruments a second helix over the 

 first, has thought he obtained from it only a current of a superior 

 order to tliat of the first. But, from such an arrangement, the 

 result is very complicated : because, in the second helix, as in 

 the first, the predominant action is due to the influence of the 

 central magnet." 



This opinion is valueless, in the face of tlie experiments above 

 recorded ; because in them the differential action of the two 

 currents was displayed quite independently of the presence of 

 the temporary magnet. If I had placed a bar of soft iron in the 

 centre of the inductive helix of large wire, the iron would have 

 become strongly magnetic, and would have re-acted upon the in- 

 duced current of the lielix, increasing its power, as may easily be 



