36 Prof. H. F. Weber on the Inductions 



the currents I or again inserted. One could thus investigate 

 in succession the action of the currents I, the action of the 

 currents I l7 and the resultant action of the oppositely directed 

 currents I and I lt It was found that the direction of the cur- 

 rents I x was always the opposite of that of the currents I, that 

 the currents I x exerted a somewhat feebler action in the tele- 

 phone than the currents I, that the resultant action of the cur- 

 rents when in the same direction amounted to nearly double 

 the action of each singly, and that the resultant action of the 

 oppositely directed currents was nearly equal to nil. M. Her- 

 mann concludes from these experiments that the phases of the 



77" 



oscillating currents I and I x cannot be displaced -x in relation 



to one another, that much rather they must nearly coincide. 



M. Hermann has, he believes, made it evident by these ex- 

 periments that neither the amplitudes nor the phases of the 

 partial tones of a sound are sensibly altered by the induction 

 that passes in the telephone, and, accordingly, that the above- 

 stated inferences from the theory of M. Dubois-Reymond do 

 not correspond with the facts ; whether, and how, the results 

 of his experiments can be brought into accordance with the 

 general law of induction he leaves undecided. 



The following communication is intended to show that the 

 experimental results obtained by M. Hermann are in most per- 

 fect accordance with the general law of induction, and can be 

 adduced as new and interesting evidence for the universal 

 validity of that law. This perfect accordance is attained as 

 soon as all the inductions that take place in the telephonic 

 circuit are taken into account. Dubois-Reymond has neg- 

 lected the induction of the telephonic circuit in regard to itself 

 as unessential ; it results from the following considerations 

 that this induction is really the determining moment in the 

 telephonic process. 



Let a telephone be in a closed circuit, and a second tele- 

 phone be inserted in another closed circuit ; let both circuits 

 be so constituted and placed that they exert upon each other a 

 powerful reciprocal induction. 



(a) For that one of the two closed circuits which contains 

 the exciting telephone T, let 



W signify the resistance of the circuit, 



I the current-in tensity of this circuit, 



Q the electrodynamic potential of this circuit upon itself, 



P the electromagnetic potential of the magnetic masses 

 in the telephone T referred to the conduction of the 

 current ; 



