EXPERIMENTS WITH THE TOPLER MACHINE. 141 



ner as the principal discharges, and hence operate to 

 make the potential of 6 Y , receiving its charge from 

 above, higher than that of Z>, receiving its charge from 

 below. This residual is not sufficient of itself to bring 

 the machine into action, but it creates a slight differ- 

 ence in favor of (7, sufficient to sustain a reversal of 

 potential when the direct rotation is resumed. 



THE F ARABIC CURRENT. The faradic current con- 

 sists of a series of electric impulses following each other 

 with great rapidity. It is obtained from the battery 

 and coil by a spring vibrator, which opens and closes 

 the circuit; and from the magneto-electric machine by 

 a revglving electro-magnet and commutator. 



Both these instruments have, for many years, been 

 extensively used in medical practice ; but the use of a 

 static machine for this purpose is quite recent, and the 

 switch, on the machine here represented, affords special 

 facilities for producing and utilizing this current. In 

 Fig. 42 are shown two sockets, on the front edge of 

 the base, connecting with the terminals of the switch, 

 into which are inserted the tips of conducting cords, to 

 the outer extremities of which may be attached metal 

 handles, as shown, or other electrodes suitable for the 

 use of this current, for medical or scientific purposes. 



As already explained, when the machine is in oper- 

 ation there is a constant movement of electricity 

 through the switch and its connections, from 1) to (7, 

 while the charge is accumulating; and the counter dis- 

 charge through them, from to D, is simultaneous with 

 the discharge above, from R to P. When the switch is 

 open and the cords attached, as shown, this discharge 

 must either force its way through the kiln-dried wood, 

 or pass out through the cords and any object connected 



