Dr. G. Bird on certain Properties of Platina Electrodes. 379 



tive or negative divergence. The discharge took place in both 

 my cases on a leaf of writing paper moistened with distilled 

 water, which was applied to the inferior plate of the condenser, 

 while another leaf of moist paper covering the upper plate was 

 touched with the fingers in order to make everything alike on 

 both sides with respect to the condenser. The most simple 

 form of the experiment might however be this ; that a zinc 

 condenser plate should be immediately touched with the moist 

 fingers, which, as others have already observed, is sufficient to 

 produce a negative shock. I do not say that this experiment 

 is as yet explained agreeably to the contact theory, but as little 

 could any one find in it a proof of the chemical theory. More- 

 over, this may be viewed in connexion with other much more 

 important experiments which promise at least a partial ex- 

 planation of it, of which, however, it is not now my intention 

 to treat. 



L. Observations on some peculiar Properties acquired hy 

 Plates of Platina^ 'which have been used as the Electrodes 

 of a Voltaic Battery. By Golding Bird, M.D.F.L.S. F. G.S.y 

 Sfc, Lecturer on Natural Philosophy at Guy's Hospital. 



THHE influence of platina positive electrodes in effect- 

 ^ ing the combination of oxygen and hydrogen are well 

 known to philosophers ; some phsenomena which may be pro- 

 bably referred to the same class have lately fallen under my 

 notice, and are interesting from their appearing to prove that 

 metals which have served as electrodes retain a polar state 

 long after connexion with the battery is broken. 



It was stated some time ago in a philosophical journal that 

 when the platina plates of the ordinary apparatus used for ex- 

 hibiting the decomposition of water by voltaic electricity on 

 the lecture table, were placed in conducting communication 

 with a piece of zinc immersed in the acidulated water with 

 which the apparatus was filled, the hydi'ogen evolved at the 

 surface of one plate was twice the volume of that given off" at 

 the other. The author of this statement added that he was 

 unable to give any explanation of the fact, nor did he offer 

 any remarks upon it. This phaenomenon appeared to be of 

 sufficient interest to deserve a more extended examination, 

 and 1 have had the pleasure of observing several curious facts 

 in connexion with it. 



Exp. 1. A glass basin was furnished with two equal sized 

 plates of platina passing through its bottom 1 '5 inches apart, 

 each connected by copper wires to a brass cup for holding 



