x 



174 Mr. E. H. M. Bosanquet on the 



(3) Directly as the mutual attraction of the two conductors 

 that limit the field, or 



(4) Directly as the electric tension of the dielectric, a quan- 

 tity that was conceived long ago very clearly by Faraday, and 

 introduced afterwards definitely into the Mathematical Theory 

 of Electricity by Professor Clerk Maxwell. 



Faraday's and Clerk Maxwell's views as to the action of the 

 dielectric in the transmission of electrostatic force, and as to 

 the state of molecular constraint that is associated with and 

 essential to that action, are very strongly confirmed by the new 

 facts of electro-optics. The dioptric action of an electrically- 

 charged medium is closely related to the electric stress of the 

 medium, the axis of double refraction coinciding in every case 

 with the line of electric tension, and the intensity of double 

 refraction varying, certainly in CS 2 and probably in all other 

 dielectrics, directly and simply as the intensity of the tension. 



Glasgow, January 22, 1880. 



XXIII. Note on the Measure of the Intensity of Sound. By 

 E. H. M. Bosanquet, Fellow of St. John's College, Oxford. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



I AM happy to say that my proposal for the establishment 

 of an acoustic laboratory* is in a fair way to be realized, 

 and I hope shortly to get to work. But I reserve all account 

 of this for the present. 



The object of this note is to present certain considerations 

 as to the expression of the measure of sound-intensities, with 

 a deduction of Fechner's law in a manner which I do not re- 

 member to have seen before. The point was suggested to me 

 by a criticism, in which it appeared to be supposed that the 

 measurement of differences of sensation arising from differ- 

 ences of intensity by the ratio of the mechanical intensities 

 was inconsistent with Fechner's law. 



The first and simplest hypothesis concerning the difference 

 of the sensations due to two mechanical intensities is, that the 

 difference of the numbers which express the measure of the 

 sensation is proportional to the difference of the mechanical 

 intensities. (The variations due to difference of pitch are 

 throughout disregarded, as that question forms a distinct 



* Phil. MW. Oct. 1879. 



