426 Prof. Connell on the Voltaic Decomposition of Water. 



the electricity actually is distributed almost uniformly over a 

 great portion of the Franklin's plate ; and near the rim, where 

 this is not the case, the principal action on the points in the 

 glass must be ascribed to the neighbouring parts of the coatings, 

 so that the conclusions before made will be approximately true*. 

 Herefrom we learn, not only that with the same quantity of 

 charge a greater electric moment is produced with the thicker 

 glass, but also that at different places the action on the glass will 

 be different ; so that the manner in which the concealed residue 

 produced by the electric moment disposes itself, cannot be very 

 different from the distribution of the electricity which is pro- 

 duced underneath the coating by the disposable charge. 



What has here been said of the Franklin's plate may, with 

 modifications suited to their forms, be oa the whole repeated of 

 the common Leyden jar ; hence it would appear that the phfe- 

 nomena of the electric residue may be completely explained by 

 the electric moment, particularly under the hypothesis that the 

 change in the glass affects its individual particles only. 

 [To be continued.] 



LXVIII. On the Voltaic Decomposition of Water. By A. Con- 

 nell, F.R.S.E., Professor of Chemistrtj in the University of 

 St. Andrews-\. 



I HAVE learned during the last few months, from that excel- 

 lent French periodical the Cosmos, that some experiments 

 lately made by M. Leon Foucault and others, showing a differ- 

 ence in the amount of hydrogen evolved from two negative poles 

 placed in water by the same galvanic current under certain 

 varieties of circumstances, particularly where the current passed 

 through acidulated water and distilled water, have been attract- 

 ing a good deal of attention, and that the appearances have 

 been thought by M. Foucault and some others to lead to some 



• The above must not be confounded with the fact, that the thinner the 

 glass is, the stronger the charge which the same constant source of elec- 

 tricity will impart to the Franklin's plate. Here, as in the condenser, the 

 theorem holds, that if the distances between the plates are very small in 

 comparison to then- magnitude, their charges ai-e almost inversely propor- 

 tional to theii- (hstances asunder ; a residt which agrees very beautifully 

 with the calculations of Clausius in his able memoir " On the distribution 

 of electricity on a single, very thin plate, and on the two coatings of a 

 Franklin's plate" (Poggendoi-ff's Annalen, vol. Ixxxvi. p. 198, x.). What 

 we have considered above is a quite different question to the one, how 

 much eleetricit)' must be present on plates, at different distances asunder, 

 in order that its potential, in reference to their interior, may ever}-where 

 be exactly the same. 



t Communicated by the Author. 



