1912.] 



on the Uii'jiii of Radium. 



101 



active substance in question. This height is magnilied and connnuni- 

 cated l)y pulleys and cords to a crayon-holder moving vertically over 



Inches 



A. LOCK-NUT. 



B. RUBBER-TYRED DISC. 



C. DISC KEPT FROM 

 TURNING WITH NUT. 



Fig. 2. 



a paper roller geared to the main shaft, the paper moving horizontally 

 in a vertical plane. The rubber-tyred nut is constantly being turned 

 down on the screw by a rough cone, driven at constant speed from 



