Mil. S. W. J. SMITH ON THE NATURE OF ELECTROCAHLLARY I'lII.NoMl-NA. 53 



in the experiments in question had on approximate value of 10 megohms. The 

 ;u ran^cinent was as in the diagram : 



-it- 



The graphite resistance could be cut out of the circuit by means of the key K. 

 For each E.M.F. applied, the direct reading with R' cut out of the circuit (as in thr 

 ordinary method of determining capillary curves), was taken ; the "indirect" reading 

 with R' in the circuit was then observed. The results for a solution of sulphuric acid 

 are shown in fig. 1. The ordinates are the scale readings of the summit of the 



Fig. 1. 



mercury column of the electrometer, and the abscisste denote the values of the 

 resistances unplugged in the resistance box W 2 . 1000 ohms correspond approxi- 

 mately to 0'28 volt. These depolarization experiments were made in June, 189G, 

 with an electrometer slightly different from that described later in the paper.* 



* These experiments were described in a Dissertation presented at Trinity College, Cambridge, in August, 

 1896. I have since fotiml that WIEDEBURO has also indicated, theoretically, the effect of depolarization. 

 ' \Viol. Ann.,' 59, 1896 (October). WIEDEWIUJ'S conclusion concerning the possible magnitude of the 

 depolarization effect is not supported by the experimental results contained in this paper. For example, 

 when the surfiice tension has its maximum value at the capillary electrode in an electrometer containing 

 a normal solution of potassium iodide, ho suggests a possible potential fall of about 0'25 volt within the 

 electrometer solution (due to n depolarization current) as a means of reconciling certain results, mentioned 

 l.-itor, with tin- ordinary I.i|>|uiiaiin Hclinholt/. theory. The actually observed dojxilurization current for a 

 KI solution is far smaller than that required to substantiate WiKDEUl'Kd'.s suggestion, and, apart from 

 this the relations established later are at variance with his view. 



