140 LIFE AND WORK OF SIR JAGADIS C. BOSE 



of the mercury. But this stops the current. The small 

 electro-magnet thus becomes inert ; the magnetic attraction 

 ceases, and the reed is set free to swing and fall anew towards 

 and into the mercury thus renewing the current and with 



FIG. io. Upper part of the Resonant Recorder. Thread 

 from clock, not shown, passes over pulley (P), letting 

 down recording smoked glass plate (G) ; C, coercing reed 

 which by its vibration sets recorder (V) in sympathetic 

 vibration. The axis of recorder (V) is supported per- 

 pendicularly at centre of circular end of magnet. S S', 

 adjusting screws ; M, micrometer ; T, tangent screw. 



it the magnet, pulling up the reed and so on. Thus the 

 desired rhythm, appropriate to the reed's length, can be 

 maintained steadily, and for any required length of time. 

 So much for the Coercer of Bose's apparatus, which has 

 to set the resonating writer in sympathetic vibration. 



This resonating writer a fine steel wire, with a bent 

 tip, and of length suitable to the required rate of vibration 

 is suspended vertically by means of pivots supported on 



