10 Prof. W. L. Bragg and Messrs. James and Bosanquet : 



In fig. 4(a), for example, the intensities of the (100) 

 reflexion through slips of various thicknesses are plotted 

 against the thickness of the slip. Since the object of the 

 experiment is to determine the position of the maximum of 



Fiff. 4. 



Thichness t a in cms. 



the curve, the intensities are relative, that given by one 

 of the slips whose thickness was 0'49 mm. being taken 

 as standard in each case. The X-rays were not rendered 

 homogeneous by a previous reflexion ; but this does not 

 affect the curves, since it was found that the allowance- 

 for " white " radiation of neighbouring wave-lengths was- 

 the same for all the slips. Figs. 4(5), 4(<?), and 4 (d) 

 are the curves for the reflexions (110), (200), and (300). 



It will be seen that the maximum of the curve occurs at a 

 progressively greater thickness in passing from one curve to- 

 that below it. Since the curves are placed in order of the 



