46 



BIOPHYSICALLY ACTIVE X-RAYS 



of the calibrated transparent scale situated below the eyepiece. This 

 scale is calibrated to read 0-25 r in half r units. It is illuminated from 

 below by the small lamp L connected to a small dry cell. The whole 



Fig. 1-18. Detailed construction of the Victoreen condenser r-meter. Small 

 thimble ionization chamber attached at C. String electrometer F is charged by 

 frictional electricity from wheel A. Huygens' eyepiece with transparent scale cali- 

 brated in roentgens inserted above T. Lamp L illuminates F and calibrated scale 

 through low-power objective 0. 



Thimble ionization chamber 

 U — 2.5 cm- 



Amber 



Amber 



^Graphite 

 Thin Bakelite 



Fig. 1-19. Removable thimble ionization chamber of the Victoreen condenser 

 r-meter. 



weighs 10 pounds. Most of the weight is attributable to the lead- 

 shielded construction. 



After the string electrometer has been charged, to read zero on the 

 r scale, the charged chamber tube (condenser), Fig. 1-19, can be removed 

 and placed in the path of the x-ray beam whose intensity one wishes 

 to measure. The x-ray tube is then activated for 1 minute. The cham- 



