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



The intensity of reflexion is that from a rock-salt face, 

 determined as described in a previous paper. It would be 

 perhaps more accurate to compare e with Q, but the com- 

 parison has been made in this way in order to facilitate the 

 application for the correction for e to our results. 



Fig. 6. 











s< 













c 



) s' 









fo 











20 40 SO 60 



Relative values of £oj 



In fig. 6, yLt is plotted against the intensity of reflexion. 

 It will be seen that the points, with the exception of (200), 

 lie on a straight line which cuts the y axis at 10*80, a value 

 very close to the normal coefficient of absorption 10' 70. 

 We may therefore assume, without introducing any large 

 error, that we can calculate for any reflexion from the 

 formula 



fJL=fJL + kl, (6) 



the value of h being determined from the slope of the 

 curve. 



The Relation between Regularity of Structure and 

 Intensity of Reflexion. 



7. An interesting point was observed in measuring the 

 intensities of reflexion through the crystal plates. In 

 the case of certain plates, the intensity was found to be 

 abnormally high. In fig. 4, the points corresponding to 

 these plates which gave the high values are denoted by 

 crosses instead of circles. This abnormality is much more 

 marked in the case of the (100) reflexions than for those 

 which are less intense. 



This effect was traced to a greater irregularitv in structure 

 of the crystal plates. In every case in which the value came 

 to be abnormally high, it was found that the crystal gave 

 reflexion over a wide range of angles. It was also found 

 that this irregularity could be produced artificially by 



