tnere ContaB of condu8ing Suh/Iances. 2C)j 



9 finger Immerfed in the water of the bafon, by tpudiiiig, 

 with the plate crafped in the other hand, the f'ouj th or cvcu 

 third pair of metallic pieces. By toucliiug then the fifth, 

 the fixth, and the red in fucceffion till I come to the la(l, 

 which forms the head of the column, it is curious to obferve 

 how the fliocks gradually increafe in force. But this force 

 is fuch, that I receive from a column formed of twenty pairs 

 of pieces (not more) {hocks which afi'ect the whole finger with, 

 confiderable pain if it be immerfed alone in the water of the 

 bafon J which extend (without pain) as far as the wriR, and 

 even to the elbow, if the whole hand, or the greater part of 

 it, be immerfed J and are felt alio in the wrift ot the other 

 hand. 



I Rill fuppofe that all the neccQary attention has been em- 

 ployed in the conilruC-lion of the column, and that each pair 

 or couple of melallic pieces, relulting from a plate of filver 

 applied over one of zinc, is in communication with the fol- 

 lowing couple by a fufficient ftratum of moilture, confifting 

 of fait water rather than common water, or by a piece of pafte- 

 board, fkin, or any thing of the fame kind well iinpreonated 

 with this fait water. The dilk muft not be too fiuall, and 

 its furface muft adhere clofely to thofe of the metallic plates 

 between which it is placed. This exa6l and exteniive appli- 

 cation of moiilened diil;s is very important, whereas the me- 

 tallic plates of each pair may only touch each other in a few 

 points, provided that their conta6l is immediate. 



All this ftiows that, if the contaft of the metals with each 

 other in fome points only be fufficient (as they are excellent 

 conductors) to give a free pali'age to a modera;e]v ftrong 

 current of eleilricity, the cafe is not the fame with liquids, 

 or bodies iAipresrnated with moifture, which are conductors 

 much lefs perfect ; and which, confequently, have need of 

 more ample conta6l with metallic conductors, and (till more 

 with each other, in order that the electric fluid ni^^v cafiiy 

 pafs, and tluit it may not be too much retarded in its courfe; 

 trpecially when it is moved with very little iorce, as in the 

 prefent cafe. 



In a word, the efleets of my apparatus, that is to lav, the 

 ^iocks felt, are couiiderably more feafible in proportion as 



the 



