236 STUDIES IN ELECTRO-PHYSIOLOGY: 



latter. Beneath it is a pin, with a milled head (Fig. 125) to 

 which the suspension is attached. Raise this 

 pin, without turning, very gently, until the mirror 

 is exactly in the centre of the opening and 

 the suspension swings freely. Then replace, 

 and adjust the controlling magnet shown 

 underneath the instrument in the figure given. 



To do this take off the screw at the top of the rod and 

 slide the magnet off. Then screw the rod into its seat, 

 replace the magnet due north and south and the screw 

 and the galvanometer is nearly ready for use. 



Should it be necessary at any time to examine the 

 suspension, first take off the two screws which clamp the 

 case to the base, remove the terminals and the ebonite 

 discs below them and the pillar, having first detached 

 the controlling device by sliding off the magnet and 

 unscrewing the rod. The case can now be lifted off 

 bodily. 



The next procedure is to remove the coil connection at 

 the left-hand inner terminal, and, also on the left, there 

 is a screw with a milled head. When this is taken out the 

 front coils will swing to the right on their hinges and expose 

 the suspension. 



Sometimes a hair, a microscopical fragment of silk from 

 the suspension, may connect some part of the latter with 

 the casing and give trouble. Upon opening the coils this 

 may be detected. 



A hole, covered by a slide, at the top of the case is for 

 the insertion of a thermometer. 



As the Kelvin galvanometer is so well known, a tech- 

 nical description of it is unnecessary. There are several 

 points in connection with it, however, to which attention 

 may usefully be called. 



If the instrument is placed in the east and facing west 

 the suspension will, before the controlling magnet is in 



