468 



Mr. J. M. Kuehne on the Electrostatic 



(fig. 3), the remainder o£ the circuit being built of best 

 transformer sheet iron. The inner dimensions of the 



Fia:. 3. 



rectangle are: height 26 cm., width 23 cm. The con- 

 denser and the portion of the magnetic circuit passing 

 through it are enclosed in a wooden box (B, B) lined with 

 tinfoil, in order to protect the movable part of the condenser 

 from air currents and electrostatic disturbances. The movable 

 part of the condenser is earthed, the stationary part insulated. 

 The magnetic circuit is energized by means of two exactly 

 similar coils (C, 0) placed around the horizontal parts of the 

 circuit outside the box. The current used is a 110 volt, 

 60 cycle alternating current. The condenser is charged by 

 the secondary of a potential transformer, the primary of 

 which is connected in parallel with the magnetizing coils. 

 The charging E.M.F. is thus very nearly 90° out of phase 

 with the magnetic field. The effect of the magnetic field on 

 the charging current passing to and from the movable part 

 of the condenser along the suspension wire and frame is 

 practically avoided by having the magnetic circuit closed so 

 that there is never an appreciable magnetic field along the 

 path of the current. The maximum result which this electro- 

 magnetic force can have is to entirely annul the effect sought 

 for in the present experiment (see p. 463, footnote). In the 

 present arrangement, therefore, it could have no more serious 

 consequence than to reduce somewhat the observed deflexions. 

 That this reduction has in fact been very slight is shown by 

 the results of the experiment. 



