ON A METHOD OF MEASURING THE 

 INTENSITY OF THE X-RAYS. 



F. W. BRANSON, F.I.C. 



Owing to the fact that aluminium is comparatively trans- 

 parent to the X-Rays, the following method was devised 

 as a convenient one for estimating the intensity of these 

 radiations. 



The method is believed to be the first devised for this 

 purpose. The instrument, which is called an X-Ray 

 meter, consists of a plate of aluminium, on which are 

 superimposed a series of steps of the same metal, each 

 step being i mm. in height. 



Fig. I. X-Ray Meter. 



To take an observation the instrument is superimposed 

 between an X-Ray tube and a fluorescent screen ; the 

 shadows of a series of steps, varying in number according 

 to the intensity of the radiations, may then be counted. 



A photographic plate enclosed in a light-tight envelope 

 may be substituted for the fluorescent screen, and a time 

 exposure given. 



The shadows of the steps will then be registered on 

 the photographic plate. By the above means various 

 forms of apparatus may be easily compared as to intensity. 



