628 Prof. W. H. Bragg and Mr. S. E. Peirce on the 



it becomes more obvious when the logarithms of the various 

 figures are set side by side. This is done in the next table. 



Table II. 

 Logarithms of atomic absorption coefficients ( + 22). 



Wave- 

 length X 10 8 . 



Absorber. 



Al. 



Fe. 



m. 



Cu. 



Zn. 



Pd. 



Ag- 



Sii. 



Pt. 



Au. 



0-491 



1-934 



1-114 



1-235 



1-338 



1-369 



2-064 



1-260 



1-377 



2-176 



2190 



0-508 



o-ooo 



1-209 



1-318 



1-369 



1-428 



1-301 



1-342 



1-473 



2-223 



2-2274 



0537 



086 



1-248 



1-354 



1-422 



1-479 



1-350 



1-394 



1-513 



2-245 



2-272 



0554 



0-079 



1-272 



1-382 



1-444 



1-510 



1-377 



1-403 



1-549 



2-312 



2 328 



0-576 



0149 



1-330 



1-446 



1-508 



1-561 



1-452 



1-477 



1-591 



2-377 



2-387 



0-615 



0196 



1-377 



1-490 



1-557 



1-619 



1-498 



1-545 



1-658 



2-386 



2-405 



It will now be seen that the differences between the figures 

 of any two columns are in the main independent of wave- 

 length, the exceptions being probably due to experimental 

 errors. The differences are set down in the next table. 



Table III. 



Wave- 

 length xio 8 . 



Fe-Al. 



Ni-Fe. 



Ou-Ni. 



Zn-Cu. 



Pd-Zn. 



Ag-Pd. 



Sn-Ag. 



Pt-Sn. 



Au-Pt. 



0-491 



1-180 



0121 



0-103 



0031 



(-695) 



-0-804 



0-117 



0799 



0-014 



0'508 



1-209 



0-109 



051 



0059 



-0-127 



0041 



0131 



0-750 



0051 



0-537 



1-362 



0-106 



0068 



0-057 



-0-129 



0-044 



0-119 



0-732 



0-027 



0-554 



1-193 



o-iio 



0-062 



0-056 



-0-133 



0-026 



0-146 



0-763 



0-016 



0-576 



1181 



0-116 



0062 



0053 



-0-109 



0-025 



0114 



0-786 



0010 



0615 

 Average ... 



l'ISl 

 1-183 



0-113 



0-067 



0062 



-0-131 



047 



0-113 



0-728 



0019 



0-112 



0-069 



0-053 



-0-126 



0036 



0'123 



0-760 



0023 



41ogN 1 /N a 



1-204 



0-128 



0-060 



0-060 



0-743 



0036 



108 



0-760 



0-024 



It will be observed that in general there is a decrease in 

 proceeding from Pd to Ag. This is an example of a rule 

 already known, viz., that the characteristic rays of any sub- 

 stance are absorbed on a higher scale by substances of lower 

 than by substances of higher atomic weight. The wave-lengths 

 of the rays here investigated are those characteristic of Ag, 

 Pd, and Eh, and they are absorbed on a higher scale by the 

 substances Al, Fe,*Ni, Cu, Zn, than by Ag, Su ; Pt, Au. " The 



