202 Faraday. 



the chemical party explained it as a consequence of chemical 

 affinity or incipient chemical action between the metals and 

 the surrounding air or moisture. There is also no doubt that 

 the continued activity of a voltaic cell is always accompanied 

 by chemical unions or decompositions ; but while the chemical 

 party asserted that these constitute the efficient source of the- 

 current, the contact party regarded them as secondary actions, 

 and attributed the continual circulation of electricity to the 

 perpetual tendency of the electromotive force of contact to 

 transfer charge from one substance to another. 



One of the most active supporters of the chemical theory 

 among the English physicists immediately preceding Faraday 

 was Peter Mark Eoget (b. 1779, d. 1869), to whom are due two- 

 of the strongest arguments in its favour. In the first place, 

 carefully distinguishing between the quantity of electricity put 

 into circulation by a cell and the tension at which this electricity 

 is furnished, he showed that the latter quantity depends on the 

 " energy of the chemical action "* a fact which, when taken 

 together with Faraday's discovery that the quantity of electricity 

 put into circulation depends on the amount of chemicals con- 

 sumed, places the origin of voltaic activity beyond all question. 

 Koget's principle was afterwards verified by Faradayf and by 

 De La EiveJ; " the electricity of the voltaic pile is proportionate 

 in its intensity to the intensity of the affinities concerned in 

 its production," said the former in 1834; while De La Kive 

 wrote in 1836, " The intensity of the currents developed in 

 combinations and in decompositions is exactly proportional to 

 the degree of affinity which subsists between the atoms whose 

 combination or separation has given rise to these currents." 



* " The absolute quantity of electricity which is thus developed, and made to 

 circulate, will depend upon a variety of circumstances, such as the extent of the 

 surfaces in chemical action, the facilities afforded to its transmission, &c. But 

 its degree of intensity, or tension, as it is often termed, will be regulated by other 

 causes, and more especially by the energy of the chemical action." Roget's 

 Galvanism (1832), 70. 



t Exp. Res., 908, 909, 916, 988, 1958. 



I Annales de Chim., Ixi (1836), p. 38. 



