The Theory of Binaural Audition. 181 



heat communicated, the inequality would depend on the diver- 

 gence of the lines of flow — although my explanation, so far as 

 it went, was quite consistent with such a necessity. 



The importance of this divergence became clearer to me in 

 November 1877 ; and I had no sooner recognized it than I 

 perceived a general connexion between the phenomena in 

 question and other phenomena of gases, particularly that of 

 transpiration, or diffusion through porous plugs. I did not 

 then publish any account of the theoretical investigation, be- 

 cause the theory indicated the existence of other phenomena 

 beyond those already known, and I wished to verify these in- 

 dications of the theory by experiment. 



These experiments have occupied considerable time ; but 

 they are now completed, and their result is (1) to verify the 

 theoretical revelations as to the existence of a class of very 

 marked and important phenomena which were, so far as I 

 know, previously unsuspected, (2) to establish certain general 

 laws which apply equally to the phenomena of transpiration 

 and those of the radiometer, and (3) to afford an absolute 

 proof that gas possesses dimensional structure (i. e. that it is 

 not a continuous plenum), the results of the experiments 

 agreeing with those deduced from the theory in the most de- 

 finite manner. A paper containing an account of both the 

 theoretical and experimental investigations has been forwarded 

 to the Royal Society. 

 January 28, 1879. 



XXXIII. The Theory of Binaural Audition. A Contribution 

 to the Theory of Sound. By Anton Steinhauser*. 



[Plate IX.] 



Introduction. 



THE theory of Audition may be divided into two portions — 

 that of Monaural Audition, or of hearing with one ear, 

 and that of Binaural Audition, or of hearing with both ears. 

 The former, already treated of in every textbook of Physics, 

 is concerned with explaining the arrangement of the human 

 ear, the function of its separate parts, and, lastly, how the ear 

 is instrumental in the faculty of hearing. The second branch 

 of the subject, which has never, to my knowledge, been yet 

 developed!, has to discuss the general question of hearing, 



* Translated and communicated by Prof. Silvanus P. Thompson. 



t [For the literature of the subject see: — 



Luca, A. — Virchow, Archiv, xxv. 1862 : "Zur Physiologie und Patho- 

 logie des Gehbrorganes." 



Rayleigh, Lord.— Proc. Mus. Assoc. 1875-76 : " On our Perception of 

 the Direction of a Source of Sound." 



Thompson, S. P.— Rep. Brit. Assoc. 1877: '" On Binaural Audition, 

 Phil. Mag. S. 5. Vol. 7. No. 42. March 1879. P 



