272 ON GALVANIC PHENOMENA. 



Objection to Bat after having acquiesced with pleasure in the merit 

 3d sectUmT S °^ tnese ^ rst two sections of Dr. Maycoek's paper, I cannot 

 do the same with regard to the third section, nor can I acqui- 

 esce in the consequences he derives from it in your No. 144. 

 But how can it be that Dr. Maycock, though he addresses 

 to you his papers, never mentions five of mine on the same 

 subject/inserted in yourNos. of June, August, October, and 

 December 1810, and January 1811, in which lhave treated, 

 from experiments, all the parts of his system? Whatever be 

 the cause of this singular circumstance, the following dis- 

 cussion of the subject comparatively to his system, which I 

 hope he will see, will certainly contribute to throw light ou> 

 the most important points of electricity and galvanism. 

 He supposes Dr. Maycock begins this subject, in the third section of 

 eleetricalstates nis ^ rst P a P er > ' n *^ e following manner: " It is an esta* 

 of metals tobe " blished fact, that from the contact and separation of dis- 

 theirsT T- " s ' m ^ ar ant ^ insulated metals there is such a change in the 

 tionj *' electrical state of each metal, that, after the separation, the 



" one is found to be positive, the others negative, in relation 

 " to surrounding bodies": Journ. vol. XXIX, p. "25. Before 

 I proceed in this quotation, I must state the question to be 

 decided, in order to direct to it the experiments. Dr. 

 Maycock supposes, that there is no electrical effect pro- 

 duced during the contact of the metals; that it takes place 

 only at their separation: Whereas I shall demonstrate by a 

 but itiscaused great number of experiments, that these effects exist only 

 tact. ' r °° n ' during the contact, and that it is owing to extraneous 



circumstances that siny effect remains after their separation. 

 Dr. May cock's I come now to the experiments by which Dr. Maycock 

 thinks to establish his system. " To determine this point,'* 

 he says, ** in place of the small plate which usually remains 

 ** on my electrometer, I adapted a copper plate about 5 

 '* inches in diameter. It is evident, that, when this appa- 

 «' ratus is placed on a common table, the copper plate will 

 " be connected with the wire of the gold leaves, but will be 

 " in every other respect perfectly insulated; and, conse- 

 " quently, that, whenever a state different from that of the 

 " surrounding bodies is produced in the copper plate, it will 

 " be indicated by the divergence of the gold leaves, 



an.d expert- " The apparatus above described being so circumstanced, 



merits with it. c< ^ a | 



