DETERMINATION OF WAVE FORM 623 



d>ad-beat moving coil galvanometer of high torque the curve 

 is drawn on a sheet of paper carried by a revolving drum. 



Referring to Fig. 387, two brushes are in metallic connection 

 when they simultaneously rest on the unshaded portion of the 



FIG. 388. Pen mechanism of Hospitalier ondograph. 



commutator; the figure, therefore, shows the connections when 

 the condenser is discharging through the galvanometer. The 

 condenser will be charged when d and d r both rest on the un- 

 shaded part of the commutator, the galvanometer connection 

 then being broken. 



:>,89. Record obtained by Hospitalier ondograph. 



The apparatus is driven by a small synchronous motor with 

 four poles, so geared to the commutator that the latter makes 

 999 revolutions while the motor makes 1,000. The result 11 

 that with each revolution the brushes, though stationary, are 



