ELECTRICAL APPARATUS. 



267 



of the phial these are shown in the cut at c and D. A 

 wire is also twisted 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 F, for the convenience of attaching 

 a chain. Price, $2.50. 



289 - Discharging or Medical Elec- 



trometer. A Ley den jar will 

 endeavor to throw off its elec- 

 tricity from the inside to the 

 outside, the more as it becomes 

 charged with greater intensity ; 

 and if the two coatings be placed 

 so close to each other that the attraction between the two 

 coatings overcome the resistance of the glass, a discharge 

 necessarily takes place. On this fact the discharging elec- 

 trometer is constructed. A is supposed to be a cross sec- 

 tion of the prime conductor of an electrical machine. B is 

 a brass cap, forming the end of the electrometer. It is made 

 with a wire beneath to fit the hole of the conductor. C is a 

 bent glass tube. D a brass ball at the end of it. E is a 

 wire with a brass ball at each end, which wire is movable 

 backwards and forwards. When a shock is to be taken, the 

 ball E is placed at a certain distance from the surface of A. 

 A is connected with the inside of the Leyden jar, which 

 communicates the shock, and the chain is connected with 

 the outside of the jar. When the jar is charged to such a 

 degree of intensity as to acquire force enough to strike across 

 from A to E, the discharge will spontaneously take place. 

 The ball at E must be set at a greater or less distance from 

 A, according to the strength of shock required. If a shock 

 is to be given to a company, when this electrometer is to be 

 used, they must form part of the circuit between the outside 

 of the bottle and the electrometer. Price, $2.00. 



Cuthbertson's Balance Electrometer (Fig. 290, next page) 

 is an excellent and elegant regulator of the strength of the 

 charge requisite for fusing different lengths of wire, expe- 

 rimenting on metallic oxides, &c. .It consists of a mahogany 

 base, A B, about eighteen inches long, and six inches wide, 

 in which are fixed two glass supports, mounted with brass 

 balls, the one, c, set in the middle of the base, and the other, 



