6z Toha en Anmal Eh&ricily. 



aqueous conduftors : but then the powers from right to left, 

 and from left to right, are again completely Oppofed to each 

 Other; confequently the eledlric ftream is impeded, and the 

 firog remains without any movement. It is, therefore, abfo- 

 lutely neceflary that two diflferent metals or conductors of the 

 firft clafs (hould be in immediate contad with each other, 

 o« the one fide, while wilh their oppofite ends they touch 

 conduftors of the fecond clafs. 



We might confider this mutual contaft of two different 

 metals as the immediate caufe which puts the eleftric fluid 

 in motion, inftead of afcribing that power to the contaft of 

 the two metals with the moift conduiSors. Thus, for ex- 

 ample, in fig. I, inftead of admitting two different a<Slions, 

 at Icaft, in regard to the magnitude of the power, one where 

 A comes in contact with a, and another where Z comes in 

 contact with a alfo, by which an eleftric current arifes in 

 the direftion from Z to A, we might fuppofe only one ac- 

 tion at the point where A comes in contaft with Z^ which 

 impells the fluid in that direction. In both fuppofitions the 

 refult, as may be cafily feen, is the fame. But though I 

 have reafons for adopting the firfl; as true rather than the fe- 

 cond, yet the latter reprcfents the propofition with morefim- 

 plicity, and it may be convenient to adhere to it in the ex- 

 planation, as it aflbrds a readier view of it. We may then 

 fay, that in the cafes of fig. 3, 4, 5, 6, 7 and 10, no efiedl 

 will be produced, becaufe here there is no mutual contaft of 

 different metals : that the efleft alfo, according to fig. 8, will 

 be null, becaafe A, on two oppofiie fides, is in contaft with 

 Z and Z, and the actions therefore are in equilibrium ; and 

 lafilvj that an eleftric current will be occafioned in fig. 9, by 

 the aftion which arifes from the conta6l of A and Z, and 

 which is cnunterafted by np other contaft of the like kind. 



Having feen the refult of eniployins; three pieces of metal, 

 or condurtors of the fird clafs, viz. two of one kind and one 

 of a different, when coir.bined fometimes in one way and 

 fometimes in another wilh condudtors of the fecond clafs^ 



6 we 



