ON ELECTRICAL EXCITATION. 281 



tween the oxygen and zinc come into play, the induction of the former or oxygen 

 towards the metal cannot be brought on and increased without a corresponding de- 

 ficiency in its induction towards the hydrogen with which it is in combination (for 

 the amount of force in a particle is considered as definite), and the latter therefore 

 has its force turned towards the oxygen of the next particle of water ; thus the effect 

 may be considered as extended to sensible distances, and thrown into the condition 

 of static induction, which being discharged and then removed by the action of other 

 particles produces currents. 



1742. In the common voltaic battery, the current is occasioned by the tendency of 

 the zinc to take the oxygen of the water from the hydrogen, the effective action being 

 at the place where the oxygen leaves the previously existing electrolyte. But Schgen- 

 BEiN has arranged a battery in which the effective action is at the other extremity of 

 this essential part of the arrangement, namely, where oxygen goes to the electrolyte. 

 The first may be considered as a case where the current is put into motion by the 

 abstraction of oxygen from hydrogen, the latter by that of hydrogen from oxygen. 

 The direction of the electric current is in both cases the same, when referred to the 

 direction in which the elementary particles of the electrolyte are moving (923. 962.), 

 and both are equally in accordance with the hypothetical view of the inductive action 

 of the particles just described (1740.). 



1743. In such a view of voltaic excitement, the action of the particles may be di- 

 vided into two parts, that which occurs whilst the force in a particle of oxygen is 

 rising towards a particle of zinc acting on it, and falling towards the particle of 

 hydrogen with which it is associated (this being the progressive period of the induc- 

 tive action), and that which occurs when the change of association takes place^ and 

 the particle of oxygen leaves the hydrogen and combines with the zinc. The former 

 appears to be that which produces the current^ or if there be no current, produces 

 the state of tension at the termination of the battery ; whilst the latter, by terminating 

 for the time the influence of the particles which have been active, allows of others 

 coming into play, and so the effect of current is continued. 



1744. It seems highly probable, that excitement by friction may very frequently be 

 of the same character. Wollaston endeavoured to refer such excitement to chemi- 

 cal action* ; but if by chemical action ultimate union of the acting particles is in- 

 tended, then there are plenty of cases which are opposed to such a view. Davy 

 mentions some such, and for my own part I feel no difficulty in admitting other 

 means of electrical excitement than chemical action, especially if by chemical action 

 is meant a final combination of the particles. 



1745. Davy refers experimentally to the opposite states which two particles having 

 opposite chemical relations can assume when they are brought into the close vicinity 

 of each other, but not allowed to combine-f-. This, I think, is the first part of the ac- 

 tion already described (1743.); but in my opinion it cannot give rise to a con- 



* Philosophical Transactions, 1801, p. 427. t Ibid. 1807. p. 34. 



MDCCCXXXVIII. 2 



