POLARIZATION OF " X" RAYS 5 



each other ; in other words, it is polarized in 

 the complete sense of the term. 



The phenomenon is easy to observe when 

 the spark is well regulated ; this means that the 

 spark must be very small and faint. 



If the focus tube is made to turn about its 

 axis, which is parallel to the cathode rays, the 

 observed phenomena do not change, so long as 

 " X " rays reach the gap. The plane of action 

 is thus independent of the orientation of the 

 anticathode, being always the plane passing 

 through the "X" rays and the generating 

 cathodic rays. 



The spark being kept in this plane, and 

 turned round from the position in which it is at 

 right angles to the "X" rays to that in which 

 it is parallel to them, we observe that the 

 effect of the " X " rays on the brightness of the 

 spark is a maximum in the first position, and 

 diminishes to nothing in the second. 



Now, an "X" ray and its generating cathodic 

 ray only determine a plane when their direc- 

 tions are different. Again, amongst the emitted 

 " X " rays, some are in a direction very nearly 

 the same as that of the cathode rays, being 



