Abstract
THE choice by the British Association of Sir William Bragg as its president for the Glasgow meeting is a particularly happy one. His genial personality, simple yet charming style of exposition—an especially important qualification in view of the great tradition behind the inaugural address—and his connexion with one of the greatest advances of scientific knowledge in our time, fit him pre-eminently for the presidential chair. Those who had the privilege of hearing his first Friday evening discourse at the Royal Institution after his return from occupying (1886–1908) a chair at the University of Adelaide, and while Cavendish professor at the University of Leeds (1909–1915), when physicists were still struggling to understand the true nature of X-rays and inclining rather to a corpuscular than to the electromagnetic undulatory explanation, will remember how clearly the position was set forth (as afterwards in 1912 in his book “Studies in Radioactivity”), and how the advent of some great impending discovery was foreshadowed which would clear up the mystery. It was not long in coming. For in the same year, 1912, that the book was published, occurred the famous discussion in the rooms of Dr. von Laue at Munich—where the University at that time included in its scientific coterie Röntgen, Groth, Sommerfeld, and Ewald—which resulted in the epoch-making experiment being tried by the two assistants, Friedrich and Knipping, of passing X-rays through a crystal and receiving the issuing rays on a photographic plate. Not only did this successful experiment fulfil the suggestion of Dr. von Laue, that the differently orientated parallel series of planes of atoms composing a crystal should act as a space-grating towards X-rays, which latter on reflection should afford some indication of the crystal symmetry, but also at once decided that the X-rays were of an undulatory nature, with wave-lengths of the same order as the dimensions of the chemical atoms.
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News and Views . Nature 122, 324–327 (1928). https://doi.org/10.1038/122324a0
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DOI: https://doi.org/10.1038/122324a0