54 J. G. MACGREGOR ON ELECTROMOTIVE FORCE OF POLARIZATION. 
Besides this unnecessarily laborious test, I more frequently applied the other, arranging 
the connections so that both cells produced deflections in the same direction and rocking 
the commutator so rapidly that, if the polarization of the cells A and B were equal, there 
must be no change in the position of the Electrometer light spot on the scale. 
In many cases in which I had got the plates to start in a satisfactory condition, although 
I kept rocking the commutator from side to side and therefore bringing the cells A and B 
alternately into connection with the Electrometer, the light spot slowly descended the 
scale, giving not the slightest indication of the moments of change from A to B. This 
could only happen in the event of the equality of the difference of potentials of the electrodes. 
In these experiments, I have restricted myself to platinum electrodes and to dilute 
sulphuric acid of various strengths. I hope by further experiments to obtain a more 
general result. 
I have to thank Prof. Tait, of Edinburgh, in whose laboratory these experiments were 
carried on, for his kindness in allowing me the use of the necessary apparatus, and his 
assistant, Mr. Thos. Lindsay, for many kind services rendered. 
