The following note refers to some experiments instituted at the request of Mr Dewar, who asked me to determine the polarisation of the Palladium electrodes whose singular behaviour he recently described to the Society.

I had just obtained one of Sir W. Thomson's most recent forms of quadrant electrometer, and it occurred to me that this must be the proper instrument for determining polarisation, as its indicacations are not affected by electric resistance, and give directly—that is, without assuming the truth of Ohm's law for reverse electromotive forces, and the consequent necessary determinations of resistance—the quantities required.