the Absorption of X-Rays. 181 



in Table TV., for which the absorption coefficients of the 

 constituent parts are more elaborately determined than in 

 respect to other elements and for which the agreement of 

 observed and calculated coefficients is also the best possible. 

 The deviations from the said law that certain authors think 

 they have found may probably be due either to the error 

 of neglecting the absorption of the lightest elements or else 

 to experimental errors. 



For reasons previously mentioned (p. 170) the values 



of fc ,tt r» found for the different elements have been re- 



a/n 2 \J 



calculated for the purpose of obtaining corresponding- 

 coefficients in relation to the atomic absorption coefficient 

 of copper ; # Cu is arbitrarily put equal to 100. For the 



elements Li-V, besides the values found directly from the 

 observations, the corrected values are also stated, which have 

 heen obtained in a way that is stated more in full below 

 (p. 187). The values given in parentheses are not included 

 in the calculated mean values. 



Table YIII. 



Atomic absorption coefficients for the elements below in 

 relation to the atomic absorption coefficient of copper. 



Z. Element. I. II. III. IV. Mean. 



1 H obs. 0-067 0090 0136 0-195 



corr. 0-00 000 000 O'OO 0-00 



3 Li obs. 0-27 0-38 0-52 0-68 



corr. 007 Oil 011 010 010 



4 Be obs. 0-39 017 073 116 



corr. 012 011 019 0"38 0"20 



5 E obs. 0-63 0-72 0'97 L24 



corr. 0-30 027 019 0-26 025 



6 O obs. 0-58 0-72 0-89 110 



corr. 0-31 0'36 0-34 032 0'33 



7 N obs. 0*75 099 L32 1-66 



corr. 0-28 0-36 037 0-29 032 



8 O obs. 113 1-30 1-46 1*67 



corr. 0-86 0*94 0'92 0'89 0*91 



9 F obs. 1-81 1-99 2'24 2-36 



corr. 118 154 L56 1-37 1'60 



11 Na obs. 2-74 2-96 3-25 313 



corr. 2-27 2-33 2*29 2*06 2'24 



12 Mg obs. 330 311 3-58 315 



corr. 3-03 305 304 267 2'95 



13 Al obs. 517 510 5*61 576 



corr. 4-84 4*95 493 478 4-87 



Phil. Mag. S. 6. Vol. 37. No. 218. Feb. J 919. O 



