250 EXPERIMENTAL INVESTIGATIONS. 



The action lowered considerably after the first few minutes, 

 but was in some degree restored every time the tubes were 

 raised so as to wash the surface of the platina, and again 

 lowered. After twenty-four hours the water had risen half an 

 inch in the tube containing hydrogen, and three-eighths of an 

 inch in that containing oxygen. In two other tubes, without 

 platina, but with the same gases, and immersed in acidulated 

 water for the same time, the water had scarcely perceptibly 

 risen ; the effect therefore could not have been due to solution. 

 The same sheets of platinum were exposed to atmospheres of 

 common air and of similar gases, i. e. both to oxygen or both 

 to hydrogen, &c., but without affecting the galvanometer. The 

 platinum in the hydrogen was made the positive, and that in 

 the oxygen the negative electrode of a single voltaic pair ; the 

 water now rose at the rate of three-eighths of an inch per hour 

 in the hydrogen tube, and proportionally in the oxygen ; when 

 the platina was not assisted by a pair of metals the oxygen 

 was absorbed in more than its relative proportion. I hope, 

 by repeating this experiment in series, to effect decomposition 

 of water by means of its composition. 



EXPERIMENTS ON VOLTAIC REACTION. 



ON the weekly evening meeting of the Royal Institution for 

 March 13, 1840, I communicated some experiments and ob- 

 servations on certain phenomena which I collated under the 

 general term Voltaic Reaction. I then stated, that in certain 

 (probably in all) cases of the development of a voltaic current 

 a reaction was induced by the voltaic force itself, and that 

 upon the cessation of the initial force the reacting force was 

 apparent in an opposed direction. I showed, moreover, that 

 the diminution or removal of this reaction was one means of 

 increasing the power of the initial current This*, reaction in 

 electrolytes (though it is by no means confined to electrolytes) 

 is what has been generally called polarisation. 



It recently occurred to me, that as one method of increasing 

 the power of the initial current was to diminish (or, as it were, 



