X-Rays and their Applications

Abstract

RöNTGEN'S discovery of X-rays at the end of the year 1895 began a new era in the history of scientific investigation. Few discoveries have so speedily been followed by important benefits to mankind in connexion with medicine and surgery, and by equally important theoretical advances. It is no exaggeration to say that our present knowledge of the structure of the atom dates from 1895, for not only did the X-rays provide a convenient means of producing ionisation in a gas, but also by their penetrating power they suggested that search for other penetrating radiations which resulted in the discovery of radioactivity. Yet on looking back it seems somewhat strange that there should have been such a long interval—about seventeen years—between the first discovery of X-rays and the introduction of a crystal as a three-dimensional diffraction grating for the analysis of the rays. We may recall the fact that there was a slightly longer interval a century earlier between the invention of the voltaic cell and the discovery of the magnetic action of the current by Oersted. To the intuition of von Laue (1912) we owe the X-ray spectrograph and the marvellous developments which have followed from its introduction by the Braggs and its improvement by other workers.

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