Subsurface Laboratory Methods 211 



increase the resolving power far beyond the best that is available today, 

 but, conversely, this increase in resolving power will be one of the limit- 

 ing factors of the microscope, because by working with very minute objects 

 it is not possible to mount particular specimens for study. Most geologic 

 techniques do not require these extremely high magnifications, however, 

 and things geologic are usually too large for these magnifications. Fur- 

 ther research in strictly geologic fields will have to be limited to par- 

 ticular problems where the microscope can be fully utilized, 



X-RAY ANALYSIS 



N. CYRIL SCHIELTZ 



Today we have developed into the greatest industrial nation in the 

 world with the highest standard of living. This is obviously because, as 

 a nation, we have been able to develop and to accept new scientific 

 methods and tools. Nevertheless, our progress has been greatly retarded 

 because we failed on many occasions to make use of new developments 

 as soon as they were available. This is true particularly of the X-ray- 

 diffraction techniques. Over three and a half decades have elapsed since 

 Laue discovered that X-rays interact with crystalline materials to give 

 diffraction effects; yet a surprisingly great proportion of our scientific 

 and administrative personnel, such as engineers, chemists, and geologists, 

 have so little knowledge concerning it that they are unaware of the possi- 

 bilities that the method offers, especially as a research tool. As a conse- 

 quence, many problems have gone unsolved or have required an excessive 

 amount of time and effort before a solution was obtained. Obviously, this 

 regrettable situation exists, at least in part, because, although the technique 

 required to make the X-ray patterns is relatively simple, rather specialized 

 knowledge and considerable experience are essential before one is able to 

 interpret the data properly. Even today many industries fail to appre- 

 ciate this fact and are attempting to undertake X-ray-diffraction studies 

 with personnel whose training is entirely inadequate to obtain satisfactory 

 results. As a consequence, this otherwise powerful research tool some- 

 times is soon grossly neglected or abandoned because the returns do not 

 justify the cost of installation and operation. In reality X-ray-diflfraction 

 studies have contributed a vast amount of valuable information to indus- 

 try and research; however, most of it has come from the laboratories of 

 our educational institutions, federal agencies, and a few large industries. 



Since this discussion is directed principally toward a reading audi- 

 ence which may have only a limited acquaintance with the method, a brief 

 discussion concerning the mechanism of diffraction appears desirable. All 

 crystalline matter is composed of atoms or molecules arranged in such^a 

 manner that they form definite families of planes in various directions 

 through the crystal. By considering primary X-rays to be reflected by 

 these planes in the face of the crystal, the Braggs were able to reduce 



