iAi^ ON THE ELECTRIC CxOLlTMH. 



the pile; but with the coluimi, these effects do not take 

 place. 

 Exp. 10. Exp. 10. The tube of the above kind, which serves in 



this experiment, is represented in the^^Kre, as suspended 

 at the point 7; its wire, 8, having a hook, held up by a silk 

 thread, which, passing over the pulley, 10, descends to a 

 thin brass plate, 11, fixed to the base of the instrument. 

 This brass piece bends forward at the top, and the silk, en- 

 tering into a notch of this projection, is stopped there by a 

 bead fixed to it. The other wire, Q, of the tube, is hooked 

 en the projecting wire, 6. In this situation of the tube, it 

 does not affect the electroscopes of the column, they conti- 

 nue to diverge as if the tube were not connected with one of 

 1 them; but when, the silk being disengaged, the hook of 

 the wire, 8, comes to vest on the hook, 5, of the column^ 

 the circulation of the electric jiuid produced through it be- 

 tween the extremities A and B is so rapid, that the rfe- 

 vergence entirely ceases in the electroscopes ; and it returns 

 oidy, when the extremity of the wire, 8, is again lifted up. 

 This shows, that the glass lubes of this kind are sensibly as 

 good' conductors an metals. 

 Permeability of T'he different conducting faculties of bodies proceed from 

 boaies to eiec different degrees of adhesion of the electric Jlnid to them : 

 ^* but beside this difference among bodies, there is another, 



which relates to permeahditi/. All the bodies, which I have 

 tried, are permeable to \\\e whole oi the electric Jiuid, ex- 

 ce{)t those that can he charged; which are impermeable \.q 

 the electric matter, and permeable only to the vector. This 

 ChavTed bo- operation, called charge, as I have explained and proved in 

 dies, my works, consists in accumulating the electric matter only 



on one side of the lamince made of these substances, by 

 occasioning a proportional diminution of its quantity on the 

 opposite surface, which is an operation of the «ec/or; and 

 the reason why other bodies cannot be charged is, that, the 

 electric matter pervading them, thougli slowly in some of 

 them, no sensible difference in the quantity ot electric mat- 

 ter can be produced between their opposite surfaces. 

 Gla^-simper- Glass, in this respect, is a remarkable substance. It is 



ftn'xd but i't ^ absolutely impermeable to the electric matter, and, being a 

 novesaloiigits solid body, it is used for insulating pillars in our electric 

 ^"^''^*' apparatusses ; 



