AN OSCILLOGRAPH FOR TEN THOUSAND CYCLES 



87 



of the wheel interrupt the light from the lamp every thousandth of a 

 second and thus trace timing lines across the sensitized paper. Every 

 tenth spoke is thicker than the intermediate ones to indicate with a 

 heavier line the hundredths second divisions. Rulings on the cylin- 

 drical lens mark horizontal lines a twentieth of an inch apart on the 

 exposed paper to give a convenient measure of the amplitudes of the 

 oscillations. 



Fig. 13 — Galvanometer element of rapid record oscillograph. 



Two motors operate the exposing, and the developing and fixing 

 mechanisms. One rotates the main drive roll, which pulls the strip 

 of paper from the unexposed roll through the light beam, and pushes 



