310 Mr Shaw, On experiments with mercury electrodes. [Dec. 8, 



plate, and the increasing surface as the copper plate of a voltaic 

 couple." This, it will be noticed, is in the opposite direction to 

 the current observed by Lippmann and Quincke. Varley further 

 states that if the mercury be made the positive pole of a weak 

 battery the motion of the electrodes will no longer give rise to 

 such currents. 



I purpose laying before the Society an account of some experi- 

 ments undertaken in the Physical Laboratory of the University of 

 Berlin at the suggestion and under the direction of Prof. Helmholtz, 

 to whom I take this opportunity of expressing my thanks, to 

 determine whether a mercury surface can be thus completely 

 depolarized and rendered neutral to dilute acid in contact with it, 

 and, if so, by what electromotive force. 



The apparatus employed in the first instance (see Fig. 1) con- 

 sisted of an inverted bell jar J., in which was a funnel F, the stem of 



Fig. 1. 



which passed through the cork at the bottom of A, and was con- 

 nected by means of an India-rubber tube with another funnel, 

 which was in the form of a wide glass tube T, with the end drawn 

 out. The tube Twas provided with a cork, through which passed 

 a glass tube E, having a platinum wire sealed in the end within T. 

 The lower part of the bell jar round F contained pure freshly- 

 distilled mercury, connected with a platinum wire sealed in a 

 glass tube, which protected the wire from the fluid (water contain- 



