Faraday's first communication on self-induction, in the Philosophical 

 Magazine of November, 1834, does not state the matter very clearly. 

 A more detailed paper read before the Royal Society on January 29, 

 1835, clearly presents the matter, including the following quotation: 



"The case, therefore, of the bright spark and shock on disjunction may now be 

 stated thus: If a current be established in a wire, and another wire, forming a complete 

 circuit, be placed parallel to the first, at the moment the current in the first is stopped 

 it induces a current in the same direction in the second, the first exhibiting then but a 

 feeble spark; but if the second wire be away, disjunction of the first wire induces a 

 current in itself in the same direction, producing a strong spark. The strong spark 

 in the single long wire or helix, at the moment of disjunction, is therefore the equiva- 

 lent of the current which would be produced in a neighbouring wire if such second 

 current were permitted." ^* 



It is interesting to note that Faraday ascribed the momentary char- 

 acter of the induced current in a secondary conductor to the develop- 

 ment in that conductor of an "electro-tonic" state, which tended to 

 oppose the flow of current. The following interesting statement is 

 made in a paper read on November 24, 1831: 



"The current of electricity which induces the electro-tonic state in a neighbouring 

 wire, probably induces that state also in its own wire; for when by a current in one 

 wire a collateral wire is made electro-tonic, the latter state is not rendered any way 

 incompatible or interfering with a current of electricity passing through it (62). If, 

 therefore, the current were sent through the second wire instead of the first, it does 

 not seem probable that its inducing action upon the second would be less, but on the 

 contrary more, because the distance between the agent and the matter acted upon 

 would be very greatly diminished." " 



Faraday then quoted experiments on an electrical conductor designed 

 to detect "a return current . . . due to the discharge of its supposed 

 electro-tonic state." These experiments were, however, unsuccessful. 

 In view of the failure of the experiments, these speculations are not 

 considered to constitute an anticipation of the discovery of self-induc- 

 tion made by both Henry and Faraday at a later date. 



Another reference which is of interest regarding early observations 

 of self-induction is the following published in the Philosophical Mag- 

 azine in 1804 under the heading "Intelligence and Miscellaneous 

 Articles." 



" Velocity of the Galvanic Fluid 



" Vassali-Eandi has lately made some experiments on this subject, as Beccaria did 

 in regard to the velocity of the electric fluid. The fluid of a pile of twenty-five pairs of 

 plates traversed in a second thirteen metres (forty-two feet and a half) of gold cord. 

 In another experiment with a pile of fifty pairs, the fluid passed along a copper wire 

 plated with silver, three hundred and fifty-four metres (1151 feet) in length, in a time 

 incommensurable: the shock in this case was three times as strong as that experienced 

 by immediately touching the two extremities of the pile." -" 



i« Experimental Researches in Electricity by ?^Iichael Faraday, Volume 1, paragraph 

 1092. 



^^Experimental Researches, Volume 1, paragraph /4. 

 20 Volume 18, p. 374. 



14 



