438 Mr Olasson, Secondary Rontgen Mays from Metallic Salts. 



absorbed by the screen (I). If a curve is plotted, having as 

 ordinates the percentage drop caused by the fixed screen (II), and 

 as abscissae the amount previously absorbed by screen (I), then 

 if the beam is absorbed exponentially, the curve obtained will be 

 a straight line parallel to the cc axis. 



■th. 



,to tells. 



200 volls. 



Fig. 1. 



III. 



Some of the curves obtained in this manner are shown in figs. 

 2, 3, 4, and 5. 



The curves obtained when the radiator ^ is a pure metal 

 are straight lines. These are inserted for comparison. The 

 curves obtained with metallic salts are all of the same Sfeneral 

 nature. They are initially horizontal and then tend downwards. 

 The point at which the curves begin to show this downward 

 tendency depends on the salt used and on the hardness of the 

 bulb. 



