THE ADDITIVE EFFECT 



53 



signal. So long as the current is flowing, the writer 

 remains in the up-position and draws a horizontal line 

 (fig. 20). At the time of make it will be noticed that, 

 owing to inertia, the writer was momentarily jerked some- 

 what above the level of this up-position. This jerked 

 line, therefore, always marks the moment of make, and 

 the horizontal line at the higher level the continuation 

 of the current. When the current is broken, the writer 

 falls suddenly to its original level. Thus a jerked up-line 

 indicates the moment of the application of the make-shock, 



Figs. 20, 21. — Records showing greater efficiency of break-shock ; 

 frequency of vibrating recorder is 20, Signal below shows 

 by up movement ' make ' and by down movement ' break.' 



and the down-line the application of the break-shock. In 

 the two accompanying figures are given records of the 

 effects of make- and break-shocks. 



Greater Effectiveness of Break-shock 



In the record (fig. 20) the secondary coil was placed at 

 the reading of 75 unit. It will be noticed that at ' make ' 

 there was no response. But there was response at ' break,' 

 which took place 'i second later, the delay being due to 

 the latent period. In the next experiment, with the same 

 plant, the coil was pushed into the reading of i. It will 

 be seen (fig. 21) that excitation was here effective at ' make/ 



