Experimental Researches in Electricity. 108 



trary direction : for it is by virtue of their increased affinity 

 for those particles, combined with their diminished affinity 

 for such as are behind them in their course, that they are 

 urged forward : and when any one particle a (Fig. II.) 



arrives at the pole, it is excluded or set 

 free, because the particle b of the oppo- 

 site kind, with which it was the moment before in combina- 

 tion, has, under the superinducing influence of the current, 

 a greater attraction for the particle a, which is before it in 

 its course, than for the particle a, towards which its affinity 

 has been weakened. 



That the decomposition and transfer of elements were 

 dependent on the chemical affinity of the substances pre- 

 sent, Faraday has shewn very distinctly by experiments on 

 Sulphuric Acid diluted with water, and combined with Soda. 

 " The variation," he remarks, " of electro-chemical decom- 

 position, the transfer of elements^ and their accumulation at 

 the poles, according as the substances submitted to action 

 consist of particles opposed more or less in their chemical 

 affinity, together with the consequent influence of the latter 

 circumstances, are sufficiently obvious in these cases, where 

 Sulphuric Acid is acted upon in the same quantity by the 

 same electric current, but in the one case opposed to the 

 comparatively weak affinity of water for it, and in the other 

 to the stronger one of Soda. In the latter case, the quantity 

 transferred is from two and a half to three times what it is 

 in the former : and it appears therefore very evident, that 

 the transfer is greatly dependent upon the mutual action of 

 the decomposing bodies." 



Having stated in general terms his theory of decomposi- 

 tion, Faraday proceeds to apply it to particular instances, 

 and in the first place shews satisfactorily why, in all ordi- 

 nary cases, the evolved substances appear only at the poles : 

 for the poles are the limiting surfaces of the decomposing 



Fig. 11. 

 ®0 O 



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