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William Henry Bragg

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William Henry Bragg (1862-1942)

Father of W. Lawrence Bragg

1942 Obituary [1]

Sir WILLIAM HENRY BRAGG, O.M., K.B.E., LL.D., D.Sc., Sc.D., D.C.L., M.A., F.R.S., who was elected an Honorary Life Member of the Institution in 1934, in recognition of his distinguished services to science, will be remembered at the Institution for his brilliant Thomas Hawksley Lecture on "The Application of X-rays to the Study of the Crystalline Structure of Materials", which he delivered in 1927. His great services to the nation were all the more valuable because of their unusually wide scope. Thus he not only made personal contributions of the very highest importance in purely scientific fields, but also continued throughout his remarkable career to give a very full and highly effective support to scientific research generally; and finally he so thoroughly mastered the art of presenting scientific phenomena to the layman that his lectures at the Royal Institution became a means of disseminating the discoveries with which he was associated to an exceptionally wide and varied audience.

Sir William was born in 1862 near Wigton, Cumberland, and received his education at King William's College, Isle of Man. He then gained a scholarship to Trinity College, Cambridge, where he graduated Third Wrangler in the Mathematical Tripos in 1884. Shortly afterwards he was appointed Professor of Physics and Mathematics at the University of Adelaide, and a few years later became associated with Sir Charles Todd, Postmaster-General and Astronomer Royal for South Australia, who had erected a transcontinental telegraph, and had begun experimental work with wireless telegraphy. It was at that time that Sir William began his first experiments with X-rays.

Early in the present century he turned his attention to radioactivity, and acquired a small quantity of radium which he used for his researches, publishing his first paper in 1906. In 1909 he was appointed to the Cavendish Chair at the University of Leeds, where he carried out further experiments on ionization in relation to X-rays. During the years 1912 and 1913 he reviewed the results of his work in the light of investigations made in Germany by von Laue and of checks on this work carried out by his son, who had recently graduated at Cambridge. As a result of these researches, Sir William devised the first spectrometer for X-rays and for the first time was able to make observations on X-ray spectra. His son (now Sir W. L. Bragg) joined him in this work and together they were able in a comparatively short time to announce the principles of X-ray spectroscopy. An immediate result of this brilliant research was the inauguration of X-ray analysis of crystal structure as a new branch of applied science.

In 1915 the Nobel prize was awarded jointly to father and son, in recognition of the importance of their discoveries. During the war of 1914-18 Sir William was engaged on anti-submarine devices, and on apparatus for the detection of submarines, working for the Admiralty at Aberdour, Scotland, and at Harwich, and returning in 1918 to London as consultant to the Admiralty. For his services he was awarded the C.B.E. in 1917 and was created K.B.E. in 1920. In the same year he was made an Honorary Fellow of Trinity College, Cambridge. After the war he became Quain Professor of Physics at University College, London; although the appointment dated from 1915, the war prevented his taking it up earlier. During the ensuing four years he continued his work on the X-ray analysis of crystals.

In 1923 he received his most important appointments: Director of the Royal Institution; Fullerian Professor of Chemistry, Royal Institution; and Director of the Davy-Faraday Laboratory. Here much of his most valuable work was done, and here also the inspiration which he provided in encouraging others in scientific researches led to the publication of a multitude of important papers on the work done at the Royal Institution. During 1929-30 Sir William was keenly interested in the rebuilding programme which was carried out there and in the following year he was the moving spirit in the Faraday Centenary arrangements. In 1931, too, he was awarded the O.M.; and through a long period of years he received a great number of high honours from universities and technical and scientific societies, both at home and abroad.

He was elected President of the Royal Society in 1935, holding that office until 1940. His life-long advocacy of scientific research was recognized in 1937, when he was made a member of the Advisory Council for Scientific Research. He continued his work as Director of the Royal Institution until his death, which occurred in London on 12th March 1942.

1942 Obituary [2]

SIR WILLIAM HENRY BRAGG, O.M., K.B.E., M.A., D.Sc, F.R.S., Faraday Medallist and an Honorary Member of The Institution, died on the 12th March, 1942, at the age of 79, and by his death the scientific world loses one of the most distinguished of its members.

Sir William was born in 1862 and educated at Trinity College, Cambridge. He went out to Australia in the early eighties to succeed Horace Lamb as Professor of Mathematics and Physics at Adelaide University. He heard quite accidentally of the post from J. J. Thomson when walking with him down King's Parade, and telegraphed his application on the last day of entry. To his great surprise he was chosen although he had no knowledge of physics. He worked hard at it on the boat going out to Australia and his success can be judged by his later contributions. He stayed in Australia until 1908 and played a large part in building up Adelaide University. In the last few years there he became interested in radio-activity, following on a request to speak on the subject at a meeting of the Australian Association for the Advancement of Science. For the first time he took up research; he carried out experiments on the distance the alpha-particles from radioactive materials travel through air; he showed that the ionization produced by gamma-rays was due not to direct action of the rays but to electrons ejected by the gamma-rays from matter. He thought of the gamma-rays as little bullets which projected electrons when they collided; thereby he foreshadowed the quantum hypothesis. He came to England to take the chair of Physics at Leeds vacated by Stroud, and there continued measurements of ionization.

In 1912 a famous paper on the scattering of X-rays by crystals was published by Laue. During the course of a discussion between Laue and Ewald (now Professor at Belfast) Laue was led to ask what would happen if electric waves much shorter than light waves were to be passed through crystals. He realized that such rays might be in the X-ray region and got two of his students to try a long shot and place a crystal in an X-ray beam. Their first attempts at reflection were unsuccessful, but a last shot at passing the rays through a crystal on to a photographic plate produced a pattern of spots showing the regular reflection of X-rays from crystal planes, which thereby laid the foundation of X-ray analysis of crystals. These experiments aroused intense interest in all countries and amongst others the Braggs, father and son, took up the work. At C. R. T. Wilson's suggestion, W. L. Bragg, then working in Cambridge, tried the experiment of reflecting X-rays from the cleavage plane of a crystal. The experiment was tried with mica, and there was tremendous excitement in the Cavendish Laboratory when a mirror reflection was obtained.

Sir William joined wholeheartedly in the research; he proved that the reflected rays were also X-rays; he built the first X-ray spectrometer to examine crystals systematically; he made the fundamental discovery that each metal used in an X-ray tube as a source of radiation gives a characteristic X-ray spectrum of definite wavelength. He measured the characteristic wavelength of these X-rays from metals and showed that they got shorter with in- creasing atomic weight. For these fundamental discoveries the Braggs were jointly awarded the Nobel Prize for Physics.

Early in the last war, Sir William was invited to go to University College, London. During the war he directed the acoustic work on submarine detection with great success. In 1923 he was appointed to the Royal Institution. While Director he was responsible for opening up the study of organic molecules by X-rays. These organic compounds are, for the most part, composed of carbon, oxygen, nitrogen and hydrogen. The hexagonal ring of 6 carbon atoms is a basic unit of many molecules, and Sir William's elucidation of the structure of naphthalene and anthracine provided the key to subsequent research. Many of us have been present at the evening discourses at the Royal Institution over which he presided for 19 years.

He had a clarity and charm of exposition which made him everywhere liked. His Christmas Lectures, "The Universe of Light," "The World of Sound," "The Nature of Things" and "Old Trades and New Knowledge" have been translated into many languages. His last work was to organize for the British Council a series of overseas broadcasts in science, and in these he took a personal part. Retaining to the end his enthusiasm for the spread of knowledge, he was, in his 79th year, still a great leader of science. We are all the poorer for his death.

1942 Obituary [3]

Sir William Bragg, O.M., K.B.E., M.A., D.Sc., F.R.S., for long the acknowledged leader of the English scientific community, died on March 12 last in his 80th year, eighteen months after completing a strenuous five-years term as President of the Royal Society.

It was difficult to realize that he had reached such an advanced age, for he retained his freshness of mind and unrivalled powers of exposition to the last, and continued, not only to direct a team of research workers, but to make from time to time original contributions of his own. A brilliant investigator in a new field of physics, he was also the most effective spokesman and advocate of the practical application of science, and an interpreter of scientific discoveries to the general public. Few men have been held in such affectionate regard by so wide a circle. Many honours came to him, but they never affected his natural modesty, and he remained one of the most accessible of men. It was fitting that he should be the recipient of the first Platinum Medal of this Institute.

William Henry Bragg was a native of Cumberland, and after attending a village school he became a pupil of King William's College, Isle of Man, where he won a scholarship to Trinity College, Cambridge, and studied mathematics, becoming Third Wrangler in 1884.

Shortly afterwards he was appointed to the chair of Physics and Mathematics at Adelaide University, although the subject of physics was new to him, and had to be studied from books on the voyage. He remained at Adelaide for 22 years, but strangely enough did no experimental research until the latter part of that period, when he became interested in the novel phenomena of radioactivity, and obtained some unexpected results, which were published in 1909.

In that year he returned to England as Cavendish Professor of Physics in Leeds University and carried out research on X-rays. The discovery by von Laue of the diffraction of X-rays by crystals in 1912 opened up a new field, but the interpretation of the patterns observed was difficult.

Bragg's son (now Sir Lawrence Bragg), working at Cambridge, gave a much simpler explanation of the phenomena, based on reflection from atomic planes, and so made a new path for the investigation of crystal structure. The elder Bragg then devised the ionization spectrometer, which proved a most powerful tool in this field, and father and son joined forces in work that became the foundation of the new science, which has rendered such great services to metallurgy and to mineralogy in revealing the way in which solid phases are built up, and in making it possible to follow the transformations which they undergo. His writings are essential sources of information on the subject.

The two authors were jointly awarded the Nobel Prize in 1915. In that year Bragg was appointed to the Quain Chair of Physics in University College, London, but he was unable to take up the post until after the war, being actively engaged in important work for the Admiralty, mainly on submarine detection. When he was able to resume teaching he again undertook research on crystals and X-rays, until he was appointed to the Directorship of the Royal Institution, which combined with it that of the Davy-Faraday Laboratory and the Fullerian Professorship of Chemistry. This position afforded full scope for Bragg's special qualities. He gathered around him a group of active scientific workers, among whom were many who have since become leaders of research in their turn, and the laboratory gained a great reputation for its steady output of brilliant and accurate original work. The Royal Institution is unique, and its function as a centre for the popularization of science was actively developed under Bragg's leadership, to which his qualities as a host largely contributed. His own lectures, including the Christmas lectures for children which have been one of its features since the time of Faraday, were marked by the utmost clarity, and were illustrated by fascinating experiments.

Bragg had the faculty of explaining even complex and difficult scientific matters in the simplest of language. This was noticeable even in his communications to learned societies, when the clear expression and entire absence of technical jargon set a standard which one would like to see reached more often.

Bragg never spoke, even at a public dinner, without saying something worth hearing, and he did much to bring home to politicians and industrialists the value of the services which science could render to the community. His audiences never felt that they were being talked down to, and he must be held responsible for much of the progress which has been made in this country in the industrial applications of science.

Sir William Bragg was appointed C.B.E. in 1917 and K.B.E. in 1920, and in 1931 he received the high honour of the O.M. He had many other honours from this and from foreign countries. To accept the duties of the Presidency of the Royal Society at the age of 74 meant a serious tax on his energies, but no choice could have been more appropriate, and under his guidance the Society came more and more to occupy its proper place as the representative body of British science, especially when the war emergency made such representation so important.

Sir William Bragg gave the Institute's sixth May Lecture in 1916, his subject being "X-Rays and Crystal Structure, with Special Reference to Certain Metals." He was elected an Honorary Member of the Institute in 1937, and, as already mentioned, it was to him that the first award of the Institute's Platinum Medal was made in 1938. - C. H. DESCH.

1942 Obituary [4]

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