ON THE ELECTRIC COLUMN. 17 1 



This great diminution in ihe frequency of the sinkings. Alteration 

 made me think of connecting the ia// 18 with the w<?g-n/ire suggested, 

 extremity of all the columns, in order to see what increase 

 it would make in the frequency : but luckily at the same 

 time it occurred to me, that, by producing a speedy manner 

 of changing this connexion of the ball for that with the 

 ground, and inversely, it would be a mode of discovering 

 variations in the electric state of the latter, by comparing in 

 a short time its effect on the strikings, with that oi the nega- 

 tive extremity of the columns. This was the occasion of the 

 last change which I made in the apparatus, as represented 

 in the Jigure, which part 1 am now going to describe. 



On the lead base 19, 19, I fixed two insulating pillars ajj.- * 

 "^' ' . . Addition to 



27, 27j and on these a brass piece 28, at one extremity of -the apparatus 

 which is fixed the ball 18, and at the other the machinery 

 for moving the horizontal silver wire 21. By this insulation 

 of the parts against which the bead and its silver ivire come 

 to strike, I can place them in a moment in communication 

 with either the ground or the yiegative extremity of the co- 

 lumn, by only changing the position of a brass wire 29, hook- 

 ed to the extremity of the horizontal brass piece. In the 

 position of this wire, as represented in the Jigure, the ball 18 

 and the silver wire 21 are in communication with the ground ; 

 and when it is wanted to make them communicate with the 

 negative extremity of the columns, I have only to take up 

 the movable wire, and to lay its end on the projecting brass 

 piece of that extremity. I was surprised to find so little 

 difference of effect between the communication of the ball 

 18 with the negative extremity of the columns, and with the 

 ground, which is a standard between the negative and posi- 

 tive states of bodies; and upon the whole this kind of ob- 

 servations opens a new and interesting field of researches. 

 Therefore, though I had but a short time to follow these 

 observations, the following journal will show at least the na- 

 ture of this phenomenon : 



May 



