Some Acoustical Experiments. 147 



the action of the cell about 15 c must be as follows : — 



Pt j ClCrCl 2 | ClCr01 2 | ClCrCl 2 | Sn, 



becoming, after connexion, 



Pt,ClCr | Cl 3 ClCr | Cl 2 ClCr | Cl 2 Sn. 



This view of the action leaves the ion CICr polarizing the 

 cell. Now if a depolarizer acts so as to remove this ion, the 

 cell will go on producing a current. The excess of chromic 

 chloride might perforin this function, forming with this ion 

 chromous chloride : 



CrCl + CrCl 3 =2CrCl 2 . 



The behaviour of the cell shows that this does not take place 

 readily. 



A similar view of the action in the cell at about 100° indi- 

 cates the presence of chromium ions as the polarizing agent. 

 At this temperature there is not much polarization ; so that 

 it appears the following chemical change takes place readily : 



Cr+2CrCI 3 =3CrCl 2 ; 



XLIII. Some Acoustical Experiments. By Chakles V. 

 Burton, D.Sc, Demonstrator in Physics, University Col- 

 lege, London*. 



I. Subjective Lowering of Pitch. 



1. A YEAR or two ago, in the physical laboratory of 

 JljL Bedford College, London, the professor, Mr. Wo- 

 mack, called my attention to the fact that a tuning-fork which 

 was being used by a student appeared to rise perceptibly in 

 pitch as the vibration died away. It then occurred to me 

 that the effect observed might be a subjective one : that one 

 result of increasing the intensity of a musical note without 

 changing its frequency, might be to depress the pitch as esti- 

 mated by ear. To determine this point I have made experi- 

 ments upon myself, and on others whose perception of musical 

 intervals was known to be reliable. 



2. Let a tuning-fork mounted on a resonance-box be 

 strongly excited by bowing, and immediately let the open end 

 of the resonance-box be brought very close to one ear, the 

 other ear being preferably closed. After a second or so, let 

 the fork and box be moved away from the ear and held at 

 arm's length, then brought close to the ear again, and so on, 

 backwards and forvvards, two or three times. If there is any 

 * Communicated by the Physical Society : read March 22, 1895. 



