354 Dr. Williamson on the Dynamics of the Galvanic Battery. 



made in an evening discourse delivered before the British 

 Association at Newcastle, "On the Dynamics of the Galvanic 

 Battery." 



Mr. Napier quotes from my discourse a paragraph illustrating, 

 in the very simple case of aqueous hydrochloric acid, some general 

 facts respecting the atomic motions which occur in electrolysis. 

 He does not deny the continuous evolution of hydrogen at the 

 negative pole, and of chlorine at the positive pole ; nor does he 

 point out any fault in my reasoning upon these well-known facts. 

 But he proceeds to apply what he mistakes for the principle of 

 my explanation to an example of his own selection, and finding 

 himself at fault, endeavours to throw the blame on me. 



His experiment is the passage of a galvanic current through a 

 solution of sulphate of copper divided by a porous diaphragm 

 into two equal portions, one copper pole being immersed in one 

 portion, while the other copper pole is immersed in the other 

 portion. He asserts that, according to my " assumed theory," 

 there must be through this diaphragm a transfer of copper 

 towards the negative pole equal to the transfer of the chlorous 

 element towards the positive pole ; whereas experiment shows an 

 exhaustion of all the salt in the negative division, and a corre- 

 sponding accumulation in the positive division. 



Not only have I made no statement implying an equal velocity 

 of movement of the chlorous and basylous atoms, but I have yet 

 to learn that the existence of such equality would in any de- 

 gree favour my argument, or that the absence of such equality 

 would militate against my argument. 



I said that the atom of hydrogen which has given up its chlo- 

 rine at the positive pole combines with chlorine from the next 

 molecule of hydrochloric acid ; and this is equally true whether 

 it moves towards the chlorine, or whether the chlorine moves 

 towards it. I certainly never took it for granted, as Mr. Napier 

 imagines, that the atoms make equal advances towards each other. 

 Indeed Mr. Napier quotes my very words : " It is unnecessary 

 to discuss at present the particular manner in which this atomic 

 motion takes place, but there is no doubt of the fact," &c. 

 I remain, 



Yours very truly, 



Alex. W. Williamson. 

 University College, London, 

 April 12, 1864. 



