234 EXPERIMENTAL INVESTIGATIONS. 



being of amalgamated zinc, &c. &c. By this means, and 

 with a small battery of the description I am about to indi- 

 cate, a traveller may carry in his pocket an electro-chemical 

 laboratory. 



I have constructed a small battery, of a circular shape, 

 consisting of seven liqueur-glasses and seven pipe-bowls ; the 

 diameter is four inches, the height one inch and a quarter ; this 

 pocket battery gives about one cubic inch of mixed gases in 

 two minutes. The form of this combination is in effect that of 

 Mr. Daniell ; the connexions, however, never need adjustment 

 but when the worn-out zinc is renewed ; and in a battery 

 which M. Becquerel and myself are about to construct I hope 

 to remedy another defect, viz. the necessity of pouring solu- 

 tions separately into each cell, which is troublesome and inju- 

 rious, from the inequality of strength which results. I have 

 entirely remedied this in a copper and zinc constant battery ; 

 but though the process be simple, it would require more 

 words to describe than a matter of such minor importance is 

 worth. 



ON VOLTAIC REACTION, OR THE PHENOMENA 

 USUALLY CALLED POLARISATION. 



Philosophical Mag.) 1840. Report of Royal Institution Lecture. 



MR. GROVE detailed the first experiments of Volta, Erman, 

 Ritter, and Davy, the more recent ones of De la Rive, the 

 explanation of these by Becquerel, and the confirmation of 

 this latter philosopher's opinion by the experiments of Dr. 

 Schcenbein, Mr. Matteucci, and Mr. Grove himself; all which, 

 as well as the experiments of Mr. Grove on the inactivity of 

 amalgamated zinc, which he proved to be due to the same 

 order of causes, have been already given in full in various 

 numbers of the ' Philosophical Magazine.' All the effects 

 which have generally been included under the term polarisa- 

 tion were proved by Mr. Grove to be traceable to one prin- 

 ciple, viz. the electrolytic transfer of elements having for 



