Production of Fluorescent Rontgen Radiation. 

 Table I. 



365 



Intensity of fluorescent 



X-radiation from 



radiator I. 



[gold leaves separated]. 



B. 



Intensity of fluorescent 



X-radiation from 



radiator II. 



[gold leaves together]. 



A. 



Ratio 

 A 

 B* 



Mean 

 X 



— in Al 

 9 

 of 

 primary. 



100 



100 



1-00 



1-8 



100 



104 



1-04 



0-8 



100 



96 



•96 



11 



100 



99 



•99 



41 



100 



99 



•99 



3-9 



100 



97 



•97 



7'5 



100 



100 



100 



4-8 



Taking mean value 

 Intensity of fluorescent X-radiation from radiator II. _ >qc . 

 Intensity of fluorescent X-radiation from radiator L 



— in Al of gold characteristic radiation experimental = 20*6 



Standard value = 21*6 



Penetrating Power of the Primary Radiation. 

 The X-ray bulb furnishing the exciting primary radiation 

 was fitted with a palladium side tube, which enabled the rays 

 leaving the bulb to be made of any desired degree of hardness. 

 The value of the mean penetrating power of the radiation was 

 obtained by finding the absorbability of the radiation scattered 

 by a thin carbon sheet, the scattered radiation from carbon 

 being almost identical with that or' the primary radiation. 

 In order to obtain the very hard rays, not only was the bulb 

 worked at its maximum hardness, but in addition thick 

 aluminium ("19 cm.) was placed in the path of the primary 

 beam so as to absorb all but the hardest rays from the bulb. The 



values for the absorption coefficient I — J in aluminium of the 



primary beam are given in column 4 of Table I. 



The importance of knowing the order of the penetrating- 

 power of the primary beam is clear from the work of Cooksey*, 

 Innes |, Sadler t, and Beatty §, which shows that the velocity 



* Cooksey, Amer. Journ. Sci. (4) xxiv. (1907). 

 t Innes, Proc. Roy. Soc. lxxxix. (1907). 

 X Sadler, Phil. Mag. March 1910. 

 § Beatty, Phil. Mag. Aug. 1910. 



Phil. Mag. S. 6. Vol. 25. No. 147. March 1913. 2 C 



