184 Experiments with a new EUffrical or Galvanic Apparatus. 



our enquiries together, I conftrufted an apparatus for my own ufe. Zinc was laminated 

 to the twenty-fourth part of an inch in thicknefs, and pure filver to the one-thoufandth 

 part of an inch, that is to fay, as thin as our flatting mills can bring it. 



Of thefe metals I made two fets, namely, fixteen pieces of filver of two inches in dia- 

 meter, and fixteen pieces of 1.8 inch diameter, with their correfpondent plates of zinc and 

 wetted card. The fmall pile was firft prepared, and whether it were that thefe thin pieces 

 were more difpofed to admit the water between the metallic faces of contaft, or from 

 whatever other caufe it may have arifen, it did not appear by any experiment, that the 

 whole fet, though fo greatly exceeding the pile of half-crowns in furface, was capable of 

 doing more in the decompofition of water, or in communicating the fhock. But this, with 

 other fafts, feems to (hew, that the repetition of the feries is of more confequence to this 

 adion, than the enlargement of furface ; and alfo that the thicknefs of the plates, though 

 it may be attended with convenience, moft probably affords no addition to the force. I muft 

 alfo add, that I have no reafon to recommend my pile, though at firft fight it feemed to 

 poffefs cheapnefs and convenience. The plates of zinc are too thin to bear frequent clean- 

 ing or renewing after corrofion of the furface, and the filver, though it is fcarcely a£ted on 

 in this fituation, is too thin to be conveniently wiped or handled. 



The fpontaneous eledricity of the doubler prefented an obje£lion to the ftridl fidelity of its 

 refults j whence I thought it defirable to give my pile a trial with the condenfer. The foot 

 oT ft and of my eleftrometer is a brafs plate truly flat, and 3.8 inches indiameter. A piece 

 of thin Perfian filk was tied fmoothly upon the face of this plate, and it was then placed 

 upon another brafs plate, upon which it was moved about horizontally, in order to accu- 

 mulate eleftricity by friflion ; the eleftrometer itfelf being ufed as the handle by grafping 

 the top. It was found that this treatment produced very weak figns of eledricity when the 

 cleclrometer was lifted up. The lower brafs plate was then placed on the top of the fmall 

 pile, and the condenfing eledrometer placed upon it. A communication was then 

 made, by means of a wire from the lower or filver end of the pile to the upper plate 

 of the condenfer, or foot of the ele£l:rometer. In this fituation it is. evident, that the 

 charge of the pile was employed in producing oppofite ftates of eleftricity in the condenfer, 

 which would be fliewn when the plates came to be feparated. The wire of communication 

 being taken away, the eleftrometer was lifted, and the leaves diverged and ftruck. It be- 

 came necefTary, therefore, to repeat the experiment, taking care to lift the ele£lrometer 

 more gradually. The divergence took place as before, and it was increafed by prefenting 

 excited fealing wax towards the bottom of the eleftrometer. And as the top of the pile 

 had by compenfation diminiftied the fame divergence, it is clear that the ele£lricity of the 

 top of the pile, viz. of the zinc, was contrary to that of fealing wax ; that is to 

 fay, the zinc was in the plus ftate. After a number of repetitions of this experiment with 

 the fame invariable refult, the pile was then carefully ovtrfet, without difturbing the rela- 

 tive arrangement of its parts ; fo that the zinc was now at the bottom, and the filver at the 



top. 



