Prof. S. P. Thompson on Binaural Audition. 383 



a . 



but it does not follow that — is also equal to this ratio, unless 



the value for y when £ = is the same in each case. 



A number of experiments were made to determine f(&)\ but 

 as the temperatures ranged only from 18° to 22° C, and they 

 are rather incomplete, I refrain from giving them fully ; the 

 results, however, seemed to indicate that f{6) = 6 2 , or that the 

 rate of change varies as the square of the temperature from 

 the zero-point ; and on this hypothesis the point of no action 

 was found to range from +2° C. to —2° C, or about the 

 temperature at which the solution would become ice. 



In conclusion, I may state that the following experiments 

 were made. An increase in the amount of H 2 S0 4 accelerates 

 the change, still obeying the law. Ferrous chloride, in pre- 

 sence of HC1, is oxidized by KC10 3 , at 18° C, approximately 

 according to the law y(a + t) = b, the discrepancies in this 

 case being caused by the difficulty of accurately determining 

 the iron by permanganate in presence of free hydric chloride. 

 Ferrous sulphate in hydric sulphate is only very slowly acted 

 on by potassic nitrate in the cold, probably being too near 

 the zero-point. 



I hope soon to give the results of some experiments on the 

 rates of change for the various chlorates, as potassic against 

 sodic chlorate, and possibly get some relation between the 

 dynamical equivalences of those salts. 



Glasgow, August 1878. 



L. Phenomena of Binaural Audition. — Part II. By SlLVANUS 

 P. Thompson, D.Sc, B.A., Professor of Experimental 

 Physics in University College, Bristol*. 



1. TN a paper read before Section A of the British Associa- 

 -L tion last year (1877) on Binaural Auditionf , the author 

 communicated the discovery of two phenomena : first, the exist- 

 ence of an interference in the perception of sound ; secondly, 

 an apparent localization of simple sounds at the back of the 

 head when led to the two ears in such a maimer that the vibra- 

 tions reached the ears simultaneously in opposite phases. The 

 present paper recapitulates the former experiments, and gives 

 some further account of the phenomena and of new methods 

 of experimentation. 



2. The existence of an interference in the perception of 



* Communicated bv the Author. 



t Rep. Brit, Assoc.' Plymouth, 1877, p. 37 ; Phil. Mag. October 1877, 

 p. 274. 



