J53 OH THE ELECTKIC COLUMN. 



purpose, the column is terminated at the top by a sianlar 

 plate, on which presses a screw in the common manner used 

 for the pile. The top of this column, which is it« positive 

 extremity, was to be connected with the negative extremity 

 of the horizontal column, and this required, that the bdx 

 containing the latter should be opened in front: I therefore 

 placed only a pane of glass on the side where the bead 

 hangs, in order to guard it against the motions of the air. 



The first use which I made of this additional column with 

 larger plates was for the following experiments. 



Fxp. 16. Exper. \6. Placing the negative (or lower) extremity of 



the column composed of the large square plates, in com- 

 munication with the ground; I connected its positive ex- 

 tremity with a gold leaf electroscope, and after having 

 observed the maximum, soon produced, of its divergence, I 

 substituted for this column 300 of the small groups of the 

 horizontal folumn, by placing the communication with the 

 ground at its middle point: this produced the same di- 

 vergence as the former, but it required more time. 



I could not compare directly the effects of the two columni^ 

 with respect to xhe. frequency oistrikings of the bead, because 

 at that time 300 groups of any size were no longer sufficient 

 for producing them; but I compared the effects of the two 

 columns, for this purpose, in thp following manner. 



Exp. 17. £xper. 17. I first repeated the observation of the strik- 



ings with the horizontal column of 600 groups, its negative 

 extremity being in communication with the ground: there 

 were 3 strikings in 5 minutes. I then took off the commu- 

 nication of this column with the ground, and connecting its 

 middle point with the positive extremity of the column of 

 300 groups of the square plates, I placed the negative 

 extremity of the latter in communication with the ground. 

 This was again 600 groups, but 300 of them were oflarger 

 plates, and there were then 7 strikings in the same time; 

 and thus was confirmed what I had judged of the effect of*^ 

 larger plates for increasing the frequency of the strikings. 



I.xp.19. Exper. 18. I now connected the new column of 300 



larger plates with the 600 groups of the horizontal column, 

 leaving the communication with the ground at the negative 

 extremity of the former. This was in a more favourable 



moment; 



