36 



first jar or surface of first plate, in contact with conductor, 

 and outside of last jar or plate in contact with the ground, 

 being considered as the proper opposite surfaces of the pro- 

 per plate, and those on which the electricities evolved by the 

 friction of the cylinder and rubber of the electrifying machine 

 are accumulated or heaped. 



" If we make a pile of the plates coated or not, and charge 

 the outside surfaces by coating thera> and connecting one 

 with the cylinder and the other with the rubber of the ma- 

 chine, we find all the conditions of the experiment complied 

 with. There is no necessity for any connexion with the ground, 

 which in Brand's can act merely as the conductor to convey 

 the negative charge of the rubber to the extreme surface. 



'■ Let us now unpack the pile, and we find that the charge 

 of the intermediate plates diminishes, as we approximate 

 towards the centre of the pile, being greatest near the ex- 

 tremes. At equal distances the charges are equal ; for the 

 charges of the first plate but one, and the last but one, will 

 as perfectly neutralize each other as the charges of the sur- 

 faces of the first and last. The same is found to be the case 

 with the surfaces of the third plates from each extreme, and 

 so on of the others ; but it is not the case with a second and 

 a third, a first and a fourth plate, and so on, no two unequals 

 as to place exactly neutralizing each other. Hence we 

 may conclude, that the charge of the intermediate jars 

 in a series, such as described by Brand, though it really de- 

 pends on inductive agency, is altogether different from that 

 kind he alludes to, which may be inferred from his erroneous 

 representation of the actual fact; and the charge of the 

 extreme surfaces is immediately the result of that action 

 only, which several electricians have called conduction, 

 arising from the connexion of these surfaces with the sources 

 of the free electric forces. 



" The fact here described appears capable of throwing 

 much light on the corpuscular arrangement of the atoms of 



