ELECTRICAL APPARATUS. 319 



Fig. 374. 



C- 8 



also t\\ isted round the outer coating of the inner tube, which 

 projects outwards sufficiently to touch the inner coating of 

 the phial. On the outer coating of the phial is fastened a 

 hook, marked c, for the convenience of attaching a chain. 

 E F G H (Fig. 3*74) is a medical electrometer; its use is to 

 regulate the strength of the shock, for this depends upon the 

 intensity with which the phial is charged, no less than the 

 size of the phial itself. H, is a socket, and a wire attached 

 to it laterally. Into this socket is cemented a bent glass 

 tube, G ; at the opposite end of this is a second socket of 

 metal, also cemented to the glass. A hole is made through 

 this socket to admit the wire, which holds the brass balls E 

 and E. This wire is capable of sliding backwards and for- 

 wards, parallel with the horizontal part of the glass tube. 

 D, is supposed to be the prime conductor. When in use, to 

 the outer ball, F, of the electrometer, and also to the hook, 

 c, of the bottle, are attached chains, leading to a pair of glass- 

 handled directors ; the upper part of which is seen in Fig. 

 374, and a pair of directors complete in the Fig. 375. 

 We will now show the use of this apparatus. The direct- 



