214 



DR. W. GEOFFREY DUFFIELD ON THE 



160 



I2 



100 



60 



3 60 



40 



DIAGRAM 2 



COPPER 



LEAD 



x ft 



4000 4200 4400 



Wave-lengths in Angstrom units. 



460O 



If we assume that the origin is on the curve representing this relation, we are 

 forced to the conclusion that the displacement varies with a higher power of the 

 wave-length, and Table IV. shows the calculated values of the constants on the 

 assumptions that the displacement varies as the 1st to the 7th powers of the wave- 

 length. 



TABLE IV. 



The smallest maximum deviation appears for the 4th power of the wave-length. 

 For higher powers there are abnormally high values for the line n ; omitting these 

 from the last three columns the values are : 



