286 



Scientific Proceedings, Royal Dublin Society. 



Writing D for the deflection of the galvanometer (one division of which 

 was equivalent to 0-0038 volt), the linear graph gives the relation : — 

 (43-6 - D)- 1 = 0-0980^ ni „ + 0'0236. 



Table II shows the correspondence of the values calculated from this 

 equation with the observations. 



Table II. 



Recovery of a Leclanche" Cell, polarised by 0'035 amp. for 16 minutes. 



The agreement is on the whole satisfactory, especially where the deflection 

 is varying rapidly. As in Table I the observed values towards the end of the 

 period of observation rise above the calculated values due to the slow creep 

 which becomes prominent at this stage. The deviations are such as may be 

 expected in the observation of a moving pointer over a scale where tenths of 

 a division have to be estimated instantaneously. Possibly some oscillations 

 of the pointer due to the motion may be superimposed on the deflection due 

 to the change in voltage. At any rate the results justify the expectation 

 that more refined methods of observation would eliminate the irregularities 

 due to the imperfections of the method used in the above experiment. 



We may therefore conclude that the empirical equation put forward to 

 represent the rate of recovery of a Leclanche cell, based as it is on imperfect 

 theoretical considerations, is substantially verified, and that it has a 

 physical significance, which remains to be explored. This conclusion is 

 supported by its application to observations on the polarisation of the 

 Weston cadmium cell, which we shall now consider. 



The Polarisation of the Cadmium Cell. 



The importance of the cadmium cell as an international standard has led 

 to careful studies of its polarisation which have been placed on record by 

 many observers. 1 



1 Barnett, "Physical Review," vol. xviii, p. 104. 1904. Smith, " Phil. Trans. R. S. 

 Lond.," series A, vol. ccvii, p. 393. Wold, " Physical Review," vol. xxviii, p. 132. 1909. 



