296 Prof. Daniell on the Cotistatit Voltaic Battery. 



conducteur quelconque au moyen de deux lames metaliiques. 

 Cette polarisation des electrodes a done lieu dans toutes les 

 piles, lorsque les lames qui compose chaque couple plongent 

 dans un meme liquide et dans un meme auge." (Pp. 437-8.) 



This hypothesis, however, though it borders upon the true 

 explanation, is not correct ; for in my first paper upon " Vol- 

 taic Combinations" (Phil. Trans., 1836, p. 116), I have shown 

 that the polarization of the plates, and the rapid decline, and 

 final cessation, of the current in batteries of the common con- 

 struction, is owing to the deposition of metallic zinc upon the 

 conducting plates. This I at first ascribed to the deoxidating 

 power of the hydrogen upon the oxide of zinc, but have since 

 adduced evidence to prove is owing to the direct electrolysis 

 of the sulphate of zinc formed. The deposit I was able to 

 detach from the platinum, upon which it had been precipitated, 

 in plates of considerable thickness. This opposition of zinc 

 to zinc in the acid is sufficient to account for the result with- 

 out supposing " the reaction of alkaline matter transported to 

 the conducting plate upon acid transported in like manner to 

 the zinc plate through the intervening fluid." It is difficult, 

 indeed, to conceive that the latter should not rather increase 

 the power of the direct current, by its action upon the zinc 

 with which it must be in contact, than produce a counter cur- 

 rent by its action upon the alkaline matter upon the distant 

 platinum plate. 



The problem of a constant battery, which M. E. Becquerel 

 says that his father has solved, is thus stated : — 



" Si done on pouvait enlever continuellement les elemens 

 alcalins et acides qui se deposent sur les lames, on aneanti- 

 i-ait le courant secondaire, et la pile aurait une intensite con- 

 stante, en tant cependant que les surfaces des lames resteraient 

 a pen pres aussi nettes et que Taction du liquide sur le zinc se- 

 rait a pen pres la meme." (P. 438.) 



It appears from the statement of M. E. Becquerel, that in 

 the year 1 829 his father contrived an apparatus consisting of 

 a glass cell or I'ectangular vessel, the interior of which was 

 divided into three compartments by two diaphragms of gold- 

 beater's skin, admitting of no communication except through 

 the membranes placed for the purpose of retarding the mix- 

 ture or combination of the liquids contained in each. 



The bottom of the cell was perforated only in the centre 

 compartment by a small opening, so that upon plunging the 

 cell into another vessel containing a conducting fluid, the li- 

 quids in the two extreme compartments would mix with great 

 difficulty : the central aperture admitted also of being closed, 

 and the middle compartment could then be filled with the li- 



