1840.] The Galvanic Battery. 1173 



tion was determined by the chemical properties of the fluid, with which 

 they were placed in contact. Facts like these were quite irreconcil- 

 able with Volta's hypothesis, and pointed clearly to the very important 

 relation which obtained between the chemical action of the fluid on the 

 immersed metals, and the development of the Galvanic energy. Dr. 

 Wollaston, by whom chiefly Volta's theory was shewn to be untenable, 

 conceived that the current of electricity was originally determined by 

 the oxidation of the zinc, that the fluid of the circle served both to 

 oxidise the zinc and to conduct the electricity which was excited, and 

 that the contact between the plates served only to conduct electricity, 

 and thereby complete the circuit. Succeeding philosophers, did not 

 receive Dr. Wollaston's views as thus stated, and Sir Humphry Davy 

 proposed another theory intermediate between that of Volta and the 

 preceding. He adduced many experiments in support of Volta's state- 

 ment, that the electric equilibrium, is disturbed by the contact of differ- 

 ent substances, without any chemical action taking place between them. 

 He acknowledged however with Wollaston, that the chemical changes 

 contribute to the general result, and he maintained that though not the 

 primary movers of the electric current, they are essential to the conti- 

 nued and energetic action of every Voltaic circle. The electric excite- 

 ment was hegun^ he thought, by metallic contact, and maintained by 

 chemical action. 



Such was the state of the question, when, in 1834, Sir Michael 

 Faraday undertook the investigation of the source of the electricity in 

 the Voltaic or Galvanic Battery. The contradictory evidence, the 

 equilibrium of opinion, and the variation and combination of theory, 

 which he found to characterise the labours of all preceding writers on 

 this subject, forced him to repeat and examine the facts stated, and use 

 his own judgment upon them in preference to receiving that of others. 

 His previous discoveries of the identity of electricity and chemical afli- 

 nity, of the power derived from the action of the Battery, with the 

 power to be overcome in any body subjected to its influence, gave him 

 the means of examining the question with advantages not before 

 possessed by any, and of which he has made such admirable use, that 

 doubt can no longer be said to obscure the subject. 



Faraday had always coincided in opinion with those who maintained, 

 that action of the Battery was continued by chemical action, and that 



