78 Galvanism, from Galvani to Ohm. 



J affinity is essentially of an electrical nature. " Chemical and 

 electrical attractions," he declared,* "are produced by the 

 same cause, acting in one case on particles, in the other on 

 masses, of matter; and the same property, under different 

 modifications, is the cause of all the phenomena exhibited by 

 different voltaic combinations." 



The further elucidation of this matter came chiefly from 



- researches on electro-chemical decomposition, which we must 

 now consider. 



A phenomenon which had greatly surprised Nicholson and 

 Carlisle in their early experiments was the appearance of 

 the products of galvanic decomposition at places remote from 

 each other. The first attempt to account for this was made in 

 1806 by Theodor von Grothussf (b. 1785, d. 1822) and by Davy,} 

 who advanced a theory that the terminals at which water is 

 decomposed have attractive and repellent powers ; that the pole 

 whence resinous electricity issues has the property of attracting 

 hydrogen and the metals, and of repelling oxygen and acid 

 substances, while the positive terminal has the power of attract- 

 ing oxygen and repelling hydrogen ; and that these forces are 

 sufficiently energetic to destroy or suspend the usual operation 

 of chemical affinity in the water-molecules nearest the 

 terminals. The force due to each terminal was supposed to 

 diminish with the distance from the terminal. When the 

 molecule nearest one of the terminals has been decomposed by 

 the attractive and repellent forces of the terminal, one of its 

 constituents is liberated there, while the other constituent, by 

 virtue of electrical forces (the oxygen and hydrogen being in 

 opposite electrical states), attacks the next molecule, which 

 is then decomposed. The surplus constituent from this attacks 

 the next molecule, and so on. Thus a chain of decompositions 

 and recompositions was supposed to be set up among the 

 molecules intervening between the terminals. 



* Phil. Trans., 1826, p. 383. f Ann. de Cliim., Iviii (1806), p. 54. 



t Bukerian lecture for 1806, Phil. Trans., 1807, p. 1. A theory similar to that 

 of Grothuss and Davy was communicated by Peter Mark Eoget (b. 1779, d. 1869) 

 in 1807 to the Philosophical Society of Manchester : cf. Roget's Galvanism, 106. 



