Apparatus and mode of use \ 29 



joint in it at D, where it is supported by a non-conductor, and where are 

 also hung two small pith balls to show whether B and T are over- or 

 undercharged after the communication is made between them. A and a 

 are the two vials; Ee is a wire communicating with the inside coating of 

 A , aCc a wire communicating with the same coating of a ; and Ff and Gg 

 are wires fastened to the outside coating of a; rRSs is a wire for making 

 a communication between B and the vial A, having joints in it at R and 5, 

 where it is supported by non-conductors, and mMNn is another wire of 

 the same kind for making a communication between T and the vial a*. 



241] In order to try the experiment I proceed in this manner: the 

 wires Dd and D8 are lifted off from the plates B and T so as not to touch 

 them, and consequently so that there is no communication between B 

 and T : the wires Rr and Mm are suffered to rest on B and T, and the 

 wires 5s and Nn are lifted up so as not to touch Ee and Ff. The vials are 

 then charged by means of the wire bt which rests on Ee and Cc, and 

 communicates by the wire Pp with the prime conductor, a communication 

 being made between the outside of the vial A and the ground, and the 

 vial a being made to communicate with the ground by the wire xyz, 

 which rests on Gg, and is suspended from the wire bt by silk strings repre- 

 sented in the figure by dotted lines. When the vials are sufficiently charged, 

 the wire bt is lifted up till xy bears against the bottom of Cc, xy being still 

 suffered to communicate with the ground as before, and the communica- 

 tion between the outside of the vial A and the ground being still preserved. 

 At the same time the wires 5s and Nn are let fall upon Ee and Ff. For 

 the sake of doing this more commodiously I make use of the silk strings 

 represented in the figure by dotted lines and passing over the pulley H. 

 A weight is fastened to the string at w, which is supported while the vials 

 are charging in such manner that the wires 5s and Nn are lifted up so as 

 not to touch Ee and Ff, and the wire bt is suffered to rest on Ee and Cc, 

 and the wire xy on Gg; and when the vials are sufficiently charged the 

 weight is let down, by which means 5s and Nn are suffered to fall down 

 upon Ee and Ff, and the wire bt is lifted up till xy bears against the bottom 

 of Cc. 



242] From what has been said it appears that whilst the vials were 

 charging, the outsides of each of them communicated with the ground, 

 and consequently the inside of each vial is overcharged and the outside 

 undercharged. As soon as the vials are charged the communication of 

 each of them with the prime conductor is taken away, and at the same 

 time the communication between the outside of the vial a and the ground 

 is taken away, so that it is entirely insulated, and, immediately after, a 

 communication is made between its inside and the ground, and at the 

 same time the body B is made to communicate with the inside of the 



* [See plan. Fig. 17, p. 137.] 



c. p. i. 9 



