1856. J and Transformations of Motive Potver. 203 



showed that the chemical combinations taking place in a galvanic 

 battery may be directed to produce a large, probably in some forms 

 of battery an unlimited, proportion of their heat, not in the locality 

 of combination, but in a metallic wire at any distance from that 

 locality ; or that they may be directed not to generate that part of their 

 heat at all, but instead to raise weights, by means of a rotating engine 

 driven by the current. Thus if we allow zinc to combine with 

 oxygen by the beautiful process which Grove has given in his bat- 

 tery, we find developed in a wire connecting the two poles the heat 

 which would have appeared directly if the zinc had been burned in 

 oxygen gas ; or if we make the current drive a galvanic engine, we 

 have, in weights raised, an equivalent of potential energy for the 

 potential energy between zinc and oxygen spent in the combination. 



The economic relations between the electric and the thermo- 

 dynamic method of transformation from chemical affinity to avail- 

 able motive power were indicated, in accordance with the limited 

 capability of heat to be transformed into potential energy, which the 

 modification of Carnot's principle, previously alluded to, shows, and 

 the unlimited performance of a galvanic engine in raising weights 

 to the full equivalent of chemical force used, which Joule has estab- 

 lished. 



The transformation of motive power into light, which takes place 

 when work is spent in an extremely concentrated generation of 

 heat, was referred to. It was illustrated by the ignition of platinum 

 wire by means of an electric current driven through it by the 

 chemical force between zinc and oxygen in the galvanic battery ; 

 and by the ignition and volatilization of a silver wire by an electric 

 current driven through it by the potential energy laid up in a 

 Leyden battery, when charged by an electrical machine. The 

 luminous heat generated in the last-mentioned case was the com- 

 plement to a deficiency of heat of friction in the plate-glass and 



" On the Heat evolved by Metallic Conductors of Electricity, and in the 

 cells of a battery during Electrolysis." — Phil. Marj. Oct. 1841. 



" On the Electrical Origin of the Heat of Combustion." — Phil, Mag. 

 March 1843. 



" On the Heat evolved during the Electrolysis of Water," Proceedings of 

 the Literary and Philosophical Society of Manchester, 1843, Vol. vii. Part 3, 

 Second Series. 



" On the Calorific Effects of Magneto-Electricity, and on the Mechanical 

 Value of Heat," communicated to the British Association (Cork), Aug. 1843, 

 and published Phil. Mag. Oct. 1843. 



" On the Intermittent Character of the Voltaic Current in certain cases of 

 Electrolysis, and on the Intensity of various Voltaic arrangements." — Phd. 

 Mag. Feb. 1844. 



"On the Mechanical Powers of Electro-Magnetism, Steam, and Horses." 

 By Joule and Scoresby. — Phil. Mag. June 1846. 



" On the Heat disengaged in Chemical Combination." — Phil. Mag. June 

 1852. 



"On the Economical Production of Mechanical EflFect from Chemical 

 Forces."— PAt7. Mag. Jan. 1853. 



