﻿X-ray Wave-lengths and their Absorption Coefficients. 411 



silver depends on the wave-length lie on a straight line 

 within errors of experiment. This was to be expected more 

 or less, because Owen has pointed out that the absorption 

 coefficient by a given absorber varies inversely as the fifth 



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power of the atomic weight of the atom emitting the radiation, 

 and we know that the latter, roughly, is inversely propor- 

 tional to the square root of the wave-length which it emits. 

 Consequently the absorption coefficient by a given absorber is 

 proportional to (wave-length) , and logarithmic plotting 

 should give a straight line. The slope of the lines in the 

 figure gives an index 3 much more nearly than 5/2 ; but the 

 range of wave-lengths in the table is too narrow for an exact 

 deduction. Measurements of the absorption coefficients in 

 terms of wave-length are being made over a much wider 

 range, and will be useful in making a correct determination 

 of the index. 



If we consider the silver curve, we see that the absorption 

 of the silver rays is not remarkable in any way ; the points 

 for the silver wave-lengths lie on the straight line passing 

 through the points for the wave-lengths of palladium and 

 rhodium. Now it is certain that the high absorption which 



