480 



Professor W. Stirlmg 



[May 10, 



even a fraction of a second, between the emission of the sound by 

 the talking machine and the movement of the lips of the speaker, 

 there is a special arrangement called the " differential " (Fig. 6) by 

 means of which any want of accord between the Phonograph and 

 camera can be immediately rectified. The differential gearing, which 

 is placed on the shaft between the Cinematograph and its motor and 

 is actuated by means of a special small motor, is provided with a 

 reversing commutator which enables the operator to control the speed 

 of the Cinematograph — either hastening or slowing its movements. 

 The speed of the Phonograph remains constant, so that all correction 

 in speed, in order to synchronise the two machines, is done by 



Arrangement for Simultaneous Production op the Cinematograph Film and 

 THE Sound Record. The " control board " is above the Phonograph or 

 Gramophone. 



accelerating or retarding the speed of projection by means of the 

 Cinematograph. By means of the differential any accidental dis- 

 placement of the Phonograph needle during the projection can in- 

 stantly be rectified. 



Fig. 7 is a schema showing the installation for projection. 1 is 

 a small dynamo with its axis prolonged to the right with its four 

 rings ; 2 is the differential gear just described, and which is driven 

 by the small dynamo 2 bis ; 3 is the clutch of the electric engaging 

 apparatus 3 bis ; while 4 is a spring arrangement for diminishing 



