23 NOVEMBER 1945, Page 14

FIFTY YEARS OF X-RAYS

SIR,—Dr. E. Ashworth Underwood's article on the above subject will confirm the layman in his common misconception that it is chiefly, or even exclusively, in the realm of medicine that Roentgen's great dis- covery has found application. The history of science is likely to show, however, that it is in the field of crystallography that by far the most fundamental consequences have resulted. The use of X-rays in this field is entirely distinct from their diagnostic and therapeutic applications and arises from the fact that atoms in crystals, and therefore in almost all solid matter, are arranged in a regular pattern, the details of which can be revealed by X-ray analysis. X-rays have lifted the study of the structure of the solid state from the realm of speculation to that of direct observation and have profoundly advanced our understanding of the nature of matter, whether it be the metals of industry, the minerals of the earth's crust, or the proteins of our bodies. It is no exaggeration to say that as a result chemistry has been completely revolutionised, and we are now for the first time in a position to understand why different materials possess their own distinctive and often profoundly different properties. This in its turn is the first step towards the syn- thesis of basically new materials with combinations of properties hitherto unimagined. Until this century the materials at our disposal have been fundamentally no. different from those available in the Iron Age. In modern plastics we see the first example of something basically different, and many examples will arise in the future from the understanding which X-rays have made possible. Well has it been said " If the im- portance of a discovery is to be measured by the consequences to which it gives rise, the discovery of X-ray diffraction must be ranked as one

of the most important in the history of science." We may be proud to think that, although the discovery was German, it was in this country that its application in the field of crystallography was first systemati-