1920] on Crystal Structure 205 



analysed. It may be possible to push the analysis still further. 

 and find in a direct manner the arrangement of the electrons around 

 the nucleus. Experiments on these lines have already been carried 

 out ; for example, Debye's experiments on lithium fluoride. 



17. I have tried to indicate the contribution which the study of 

 crystals has made towards the solution of the problem of atomic 

 structure, and the lines on which it may be expected to afford a still 

 greater insight into that problem in the future. In considering the 

 broadest aspects of the question it has been impossible to avoid 

 generalizations to which many exceptions occur. I hope, however, 

 to have shown that crystal structure has a wider significance than 

 may perhaps be obvious at first sight. In a crystal the atoms 

 and atomic groupings are ranged in perfect geometrical regularity, 

 and it is by observing their concerted effects on the X-rays that we 

 can investigate the intimate structure of solid bodies. 



[W. L. B.] 



