Miscellanies. 179 



some of the experiments a plate of tin in lieu of the zinc, and cover- 

 ed their surfaces with a thin coat of varnish. One of these plates 

 was screwed to a gold leaf electrometer. The effect of the mois- 

 ture of the hands was in this manner excluded, and in order to 

 obviate the objection of atmospheric agency, the apparatus was pla- 

 ced under a receiver, and so adjusted that the experiment could be 

 made either in a vacuum or in a dry atmosphere of any kind of gas. 

 It was thus found that whether the electrometer with the condenser 

 was surrounded with common air, moist or dry, with oxygen, azote, 

 carbonic acid, hydrogen, or carburetted hydrogen, the results ivere the 

 same. Under these varying circumstances the electric tension was 

 found to be the same ; and it seems impossible to ascribe the effects 

 to any thing but the contact, and a sound philosophy would lead to 

 the inference that the circumstances which alone did not vary must 

 be taken as the cause of the phenomenon, namely, the recipro- 

 cal contact of the metals themselves. To succeed well in these 

 experiments, the condenser must be very perfect, the metallic plates 

 made very smooth and even, and then covered with a very thin coat 

 of amber varnish. With an instrument which condenses three hun- 

 dred times, and with gold leaves of one sixth of an inch wide and 

 two inches long, Prof. P. commonly obtained a divergence of half 

 an inch. 



To the^e direct proofs that chemical action is not necessary in 

 the production of the electricity of contact, may be added indirect 

 arguments drawn from facts which M. de La Rive has not explained. 

 If it js chemical action exerted upon an oxidable metal which is the 

 source of electricity, whence proceeds the difference of the elec- 

 tric charge of the condenser in employing different plates, such as 

 silver, copper, tin, lead, touched in all cases with the same zinc plate? 

 How shall we explain the series of tensions which the metals, their 

 sulphurets and some of their oxides form, and the fixed law of this 

 series estabhshed by Volta, and confirmed by so many experimen- 

 ters. It is well ascertained that copper is near the middle of this 

 series, the extremities of which, are, on one hand hyperoxide of 

 manganese, and on the other zinc (abstracting the metals of the 

 alkalies and earths which are below zinc). If in the contact of 

 zinc and copper it is the oxidation of the zinc which produces elec- 

 tricity, how is it produced in the contact of copper and gray man- 

 ganese ? Another fact appears irreconcilable with the chemical theo- 

 ry, according to which the energy of the electric current ought to be 



