4:68 Mr. Gr. H. Livens on the Intrinsic 



the word clamping is often used in a sense not sufficiently 

 clearly defined. When, however, he implies that the varia- 

 tion of: the sharpness of resonance with a change in pitch, 

 the coefficient of resonance remaining constant, has hitherto 

 been disregarded, I beg leave to offer a slight correction. In 

 several works on the resonance-theory of hearing * I have 

 suggested essentially the same definitions and distinctions 

 with regard to damping that Prof. Barton now offers. I have 

 in particular frequently availed myself of the fact that the 

 sharpness of resonance, the coefficient of damping remaining 

 constant, increases with the proper frequency of the 

 resonator. 



Whereas Helmholtz in his theory of hearing assumes that 

 all the resonators of the ear have the same logarithmic decre- 

 ment, that they have, therefore, disregarding certain neg- 

 ligible factors, the same sharpness of resonance, I have 

 suggested and critically examined the hypothesis that it is 

 not the logarithmic decrement, but rather the damping co- 

 efficient of all the resonators of the ear for the ordinary 

 compass of the audible scale, which remains approximately 

 the same. 



In working out this theory I have calculated quantitatively 

 the dependence of the sharpness of resonance on the proper 

 frequency of the resonator, and should like to remark in 

 this connexion, that all observed facts which have come to my 

 notice agree better with my theory than with that of 

 Helmholtz. 



LIU. On the Intrinsic Optical Activity of Isotropic Media. 

 By G. H. Livens f. * 



TflHERE are three different possible forms of the electron 

 A theory of the intrinsic optical rotatory power found to 

 be associated with certain substances ; the first is that given 

 by Drude in his Optik (ch. vi.): the second is a mixture of 

 this one and the third, which was developed by the author, 

 following a suggestion from Prof. Lorentz J. The object of 

 the present paper is to decide which of these three satisfies 

 most satisfactorily the test of experiment. Such a decision 



* E. Waetzmann, Die JResonanztheorie des TIdrens als Beitrag zur 

 Lehre von den Tonempjindungen, Vieweg u. Sohn, Braunschweig, 1912 ; 

 Bemerkvng iiber die Diimpfung der Ohr-resonatoren, Sitzung der Schles- 

 ischen Gesellschaft vom 28 Mai, 1913. 



t Communicated by the Author. 



X Livens, Phil. Mag. June 1913. 



