TIME-RECORDER. 



173 



the recording surface. This avoids the overlapping of the 

 time curve which otherwise happens. 



On un-short-circuiting the secondary circuit, and breaking 

 the primary one, the muscle contracts, and at the same 

 time the style of the electro-magnet is attracted and records 

 the exact moment of stimulation (Fig. 61). 



5. Time-Recorder (Fig. 67). This is merely an electro-magnet 

 introduced into an electric circuit, and the magnet, B, is so 

 arranged as to attract a writing-style, L. 



vv 



vv 



Fig. 67. Time-Marker. L, Lever ; B, electro-magnet bobbins; S, support; 



W,W, wires. 



6. Deprez' Signal (Fig. 68). This small electro-magnet has so 

 little inertia that, if it be introduced into an electric circuit, its 

 armature, which is provided with a very light writing point, 

 vibrates simultaneously with the vibrations of an electric tuning- 

 fork introduced into the same circuit. Arrange the signal 



EM 



Pt 



Fig. 68. Signal and Vibrating Tuning-Fork in an Electric Circuit. D, 

 Drum ; C, signal ; EM, electric tuning-fork ; Pt, platinum contact. 



and tuning-fork as in Fig. 68. The drum must move more 

 rapidly, the more rapid the vibrations of the tuning-fork used. 



