PROFESSOR IN BERLIN 313 



that interested me too, for in the long run it is better they 

 should find me too learned, rather than too trivial.' 



This left him little time for researches in electrodynamics 

 and electrochemistry, and this year he only published two 

 very interesting points supplementary to his earlier work in 

 acoustics and optics. 



The discovery of the telephone was a great surprise to him 

 at first, but he soon grasped its scientific principles. 



The thing seemed to him so obvious, he wrote to du Bois, 

 that he had not felt it necessary to form any theory about it ; 

 but then of course he had for years gone to bed and got up again 

 with Fourier's series in his mind, and could not reason from 

 himself to other people in this case. 



Du Bois had immediately after the production of the tele- 

 phone explained the appreciation of timbre by this instrument, 

 by saying that he pictured every sound as analysed into its 

 partial tones, basing his opinion on the fact that each of these 

 partial tones was conveyed to the hearer's telephone by the 

 electrical vibrations of the conducting wire, with alteration of 

 phase indeed, but with the same frequency and relative ampli- 

 tude. Since displacement of phase, according to Helmholtz's 

 earlier acoustical conclusions, is immaterial to the quality of the 

 sound, the timbre of the spoken sounds is not interfered with. 

 Hermann set up an experiment designed for a fresh theoretical 

 verification, in which a current-producing telephone was closed 

 by one wire of a coil wound with two parallel wires, while the 

 second wire, wholly insulated from the first, was either con- 

 nected directly with the observer's telephone, or with a wire 

 from a second double-wound coil, the other wire of which led to 

 the observer's telephone. Now by the known law of electro- 

 dynamic induction, the E. M. F. is proportional to the differen- 

 tial quotients of the current-intensity by the time. But since 

 with the differential quotient of the sine of a linear function of 

 the time, the multiplier of the time participates as a factor in the 

 amplitude, Hermann concluded that in this transfer of electri- 

 cal oscillations by induction in each of the double coils, the 

 amplitude of the electrical oscillations, which correspond to the 

 higher partial tones of each sound, would increase, as compared 

 with those of the deeper, in proportion to their greater fre- 

 quency. Since on the one hand the ratio of the intensities of 



