154 BELL SYSTEM TECHNICAL JOURNAL 



must be included although it does not properly belong in a paper on X-ray- 

 techniques. Dr. Davisson took an electron diffraction photograph of a 

 quartz plate that had been lapped with 303 § emery, water rinsed, and air 

 dried. The plate was then scrubbed vigorously with soap and water and 

 toothbrush and a second photograph was taken. The two photographs are 

 reproduced in Fig. 13. The first shows a series of continuous rings indicat- 

 ing the presence of a large number of small particles of quartz with random 

 orientation. In the second photograph, these rings have disappeared and 

 there remain only arc-segments associated with spots. The spots are the 

 "reflections" from undisturbed quartz. The arcs represent quartz rotated 

 through a small range of angles from this position, the misoriented material 

 indicated by the Davisson photographs with the single crystal spectrometer. 

 These electron diffraction photographs show that a lapped plate has ran- 

 domly oriented quartz on its surface which may be removed by scrubbing 

 and quartz with limited misorientation which is not removed by scrubbing. 

 No X-ray technique has shown the existence of the randomly oriented 

 material. 



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