574 



Mr Whiddington, Preliminary note on the 



Preliminary note on the properties of easily absorbed Rontgen 

 Radiation. By R. Whiddington, B.A., Allen Scholar, St John's 

 College. (Communicated by Prof. Sir J. J. Thomson.) 



[Received 2 August 1910.] 



The present note is intended to give a brief outline of results 

 obtained by the writer during the course of investigating the 

 properties of very soft Rontgen radiation and to indicate the 

 direction which the research is taking. 



A study of the literature bearing on primary Rontgen radiation 

 revealed the fact that what little work has been done on the subject 

 did not include quantitative investigations into the properties of 

 such soft radiations as are to be referred to below. Apparently 

 the softest radiation ever quantitatively studied is the character- 

 istic chromium radiation of mass absorption coefficient in 



aluminium 



(^) 



136^ 



The form of apparatus used in the experiments on the softest 

 radiation is indicated in the figure -j-. 



When the tube is evacuated to a convenient point a potential 

 applied between G and A — G being the cathode — produces a 

 stream of cathode rays which strike the anticathode A. A is one 



* Barkla, Phil. Mag. 1909, vol. xvii. p. 749. 



t For potentials higher than 4000 volts a different form of tube is found to be 

 convenient. 



