the Absorption of X-Rays. 197 



wave-length. Now, as the mean wave-lengths employed in 

 my experiments have only comprised a relatively limited 

 wave-length range (A- = # 38-0'30), the said experiments do 

 not afford sufficiently safe starting-points for judging the 

 connexion between absorption due to the outer electrons 

 and the wave-length. Barkla and White have in their 

 above-mentioned work given the results of a set of obser- 

 vations regarding — for Cu, Al, and H 2 0, comprising a 

 very large wave-length range. In the table below we find 

 again both the values taken from the said work for — of 



Cu and H 2 and the values of ^ Cu / H q ai *d q calculated 



by that means. The last-mentioned values have been 

 obtained by aid of the value of ~k ,« for Ou and 0, 



Table XII. 



"■Cu/HjjO 



a.uu V v,c 



j 



L 11 Ulll til 



O UfclUlC KJL 



jjcii ivia c 



X. 



p Cu- 



~E 2 0- 



K Cu/H 2 



Q- 



? p Cu 



0-504 



18-10 



0-539 



118-7 



-0-011 





0-499 



17-7 



0524 



119-4 



-0-012 





0-477 



15-4 



0-479 



113-6 



-0 005 





0-468 



1455 



0-473 



108-7 



+0-002 





0-460 



13-75 



0-436 



111-5 



-0-002 





0-454 



1310 



0411 



112-7 



-0 004 





0-437 



11-6 



0-400 



102-5 



+ 0-011 





0-433 



11-2 



0-388 



102-0 



0012 





0-419 



9-98 



0-371 



95-1 



0-024 





0-409 



9-28 



0349 



94-0 



0024 





0-400 



855 



0329 



921 



0030 





0-390 



7-82 



0-302 



91-5 



0-031 





0-387 



7-61 



0-312 



86-2 



0042 





0376 



6-90 



0335 



72-8 



0-078 



0-538 



0-359 



5-87 



0-311 



66-7 



o-ioo 



0-587 



0-346 



517 



0314 



58-2 



0137 



0*709 



0320 



4-54 



0270 



59-4 



0131 



0-594 



0-299 



3-71 



0-271 



48-4 



0-196 



0-727 



0-283 



3-20 



0-253 



44-7 



0-226 



0-723 



0-266 



2-77 



0-226 



43-3 



0238 



0-660 



0-250 



233 



0229 



35-9 



0-320 



0-722 



0-229 



1-86 



0-203 



32-4 



0-376 



0699 



0-222 



1-71 



0-204 



29-6 



0-423 



0-723 



0-187 



1-20 



0-196 



21-6 



0-645 



0-774 



Phil. Mag. S 



6. Vol. 



37. No. 



218. Feb. 



1919. 



Mean. 



> 0-678 



