Voltaic Battery, in Reply to Mr. Daniell. 331 



answer that he was not guided by the works of his predecessors 

 in the construction of his battery, and that the principles upon 

 which it rests are different from those which my father had 

 long since admitted. He states, for example, that the rapid 

 diminution, as well as the definitive cessation of the cur- 

 rent in ordinary batteries, are due to the deposition of zinc 

 on the negative plates of each couple. "We agree perfectly 

 upon this point; the annihilating action produced by the 

 presence of the zinc comes under that designated by the term 

 polarization of the electrodes. In my Notice, indeed, I men- 

 tion, p. 438, in the eighth and following lines, that " each 

 negative plate (of copper or of platinum) retains on its sur- 

 face alkaline elements, such as hydrogen arising from the de- 

 composition of water, and bases arising from the decomposi- 

 tion of saline matters dissolved in water." This phrase does 

 not exclude any of the bases ; the zinc therefore arising from 

 the decomposition of the salt of zinc must equally be deposited 

 on the negative plate. This deposition being effected, the 

 action of the liquid on the zinc necessarily gives birth to a 

 counter- current which more and more destroys the action of 

 the first; in order to have an apparatus of continued force, it 

 was necessary to prevent the zinc and the alkalies from being 

 deposited on the negative electrodes. 



Mr. Daniell afterwards says that the passage of the electric 

 current across diaphragms of bladder is well known to expe- 

 rimentalists ; he quotes Dr. Ritchie as having made use of 

 them. To which I reply, that the use of diaphragms in physics 

 is very ancient, since one of the Bernoullis had already se- 

 parated two different liquids by a membrane, in an experi- 

 ment in which he wished to produce an effect of endosmose. 

 Porrett also adopted the same expedient in order to show 

 that in separating, by means of a membrane, a mass of water 

 into two parts, into each of which a plate of platinum was 

 plunged communicating with one of the poles of a battery 

 pile, the water passed from the positive into the negative 

 compartment. 1 might still quote other examples ; but the 

 use of membranes, of diaphragms permitting the current to 

 pass in order to obtain a couple giving a constant current, 

 was brought into use by my father nine or ten years before 

 Mr. Daniell was occupied with this question, and particularly 

 in the experiments communicated to the Academie des Sciences 

 on the 23rd of February, 1829*. 



As to the publication of Dr. Ritchie in the Philosophical 

 Transactions, it is of the month of May 1829, and conse- 

 quently some months later, I therefore look upon Mr.Daniell's 



* Ann. de Vhys. et de Chimie, t. xli. 

 Z2 



