DETERMINATION OF WAVE FORM 621 



A dead-beat galvanometer with a good law of deflection and 

 a well-defined zero is used. 



The record is made on a photographic plate which is moved 

 vertically by a fine wire wound on a drum, seen in Fig. 384, just 

 in front of the lower worm-wheel. This drum can be thrown in 

 gear by a pin clutch. 



FIG. 386. General Electric Co. wave meter. 



The adjustable condenser allows one to adapt the apparatus 

 varying conditions, so the e.m.f. curves may be taken directly, 

 id the current curves by the use of a drop wire, as indicated in 

 j. 385. 



The General Electric Co.'s wave meter 5 is in effect similar 

 the above device. The motion of the brushes and of the pho- 



