Many people have collaborated in the attempt to collect raw material for this 1986 Bragg Centenary. It has not been a straightforward task even to attempt to collect complete and accurate data over the 100 years since 1886. There are inconsistencies between Acts, Statutes, decisions by the Council, Registrarial practices and so on, not to mention the (wholly understandable) vagaries of departmental approaches to their origins and histories.

Most of us engaged in this exercise are (well-intentioned) amateurs and, as such, have felt privileged to assemble the material for plundering in good time by the real professionals. We have been awed by the professional expertise by Rod Home, Susan Woodburn and Pamela Runge but we have had to press on, regrettable errors and omissions no doubt notwithstanding. We hope that we have prepared a reasonable base for serious reflection and scholarship.

The graduate list presented herein is that of the Bragg Centenary Commemoration Programme supplemented by those past B.Sc. students who have responded to our public call to identify themselves with one or the other of the three departments involved. With regard to Prize and Scholarship winners we have deliberately restricted ourselves to achievements whilst in Adelaide.

Certain biographical material was available for some of the many graduates and staff who have achieved distinction in other parts of the world. That material is insufficiently complete to justify inclusion. For the time being, it is regretted that names will have to speak for themselves.

The essential criterion applied in the listing of academic staff has been that the positions and incumbents should have been listed in the University Calendars. Records of distinguished visitors are very incomplete and partial listing was judged to be invidious; the same is true of the general staff many of whom served with distinction over many years. It is to be hoped that this regrettable defect will be corrected, and quickly.

The Committee that conceptualized these Celebrations, under the general stewardship of

W.G. Elford, was:‑

P. Berry‑Smith

A. Del Fabbro

A. Ewart

H.S. Green

R.B. Potts

S.G. Tomlin

E.H. Medlin (Chairman)

Thanks are due and acknowledgement is made to the following for their generous services:-

Peter Berry-Smith, Basil Briggs, Don Creighton, Albert Del Fabbro, Graham Elford, Alan Ewart, Maxine Ewart, David Fearnside, Oliver Fuller, Mary Genovese, Wayne Hocking, Rod Home,

John Jenkin, Keith Merry, John Prescott, Pamela Runge, Peter Schebella, Arlene Shaw, Stan Tomlin, Rosemary Vasey and Susan Woodburn. The dedication of Alan and Maxine Ewart, of Albert Del Fabbro and of Arlene Shaw is particularly acknowledged.

The Celebrations have been strongly supported by "The University of Adelaide Foundation" and our gratitude is expressed and hereby recorded.

Finally, the whole occasion has been endorsed as an Official South Australia Jubilee 150 Event. The discipline of physics is now practiced in three buildings. The main Physics Building was the first gift of a building (1926) to the University by the State Government and commemorates its Diamond Jubilee this year. The other two buildings commemorate two of our greatest scholars, namely Sir William Bragg and Sir Mark Oliphant. We are privileged to share our Celebrations not only with the comet but also with the community, which we aim to serve, and especially during this Official Event with our presentations from Professors Stephen Bragg, Frank Close, Paul Davies, Freeman Dyson and Brian Matthews.

Harry Medlin. 1 April 1986.

THE JOHN MURTAGH MACROSSAN MEMORIAL LECTURE FOR 1950*

THE

LIFE AND WORK OF

SIR WILLIAM BRAGG

Sir Kerr Grant

Emeritus Professor of Physics

University of Adelaide

*Reproduced by courtesy of the University of Queensland.

INTRODUCTION

The celebrated autobiography of Benvenuto Cellini begins with the words "it is the duty of all men who during their life‑time have accomplished anything of merit to write an account of their life with their own hand". In default of such a self‑recorded history it may perhaps be said with equal justification that this obligation devolves upon the contemporaries or successors of a famous man to see that the story of his life and deeds is fully and faithfully recorded in order that posterity way know what manner of man he was to whom it owes a debt of service or achievement. This public duty is, in fact, one of those specifically laid down in the terms under which the John Murtagh Macrossan Foundation was established, and it has been previously honoured on many occasions in this series of lectures.

In selecting the "Life and Work of Sir William Bragg" as another to be commemorated under this Foundation, the Professorial Board of the University of Queensland has made no unworthy choice; in honouring me with an invitation to undertake the task, reason was doubtless found primarily in the fact of my succession to him in the Chair of Physics in the University of Adelaide.

The association thus entailed with his former colleagues on the staff of the University, his relatives and friends in Adelaide, and old students who attended his classes does indeed place me in a privileged position to obtain from them and from other sources, first‑hand information concerning the man himself and the details of his life while he lived among them; further, it was, no doubt, assumed that a Professor of Physics might be expected to posses, at the least, a general acquaintance with those aspects of Physical Science, to which, in the main, Bragg's researches and discoveries belong.

I can only hope that such advantages ass I may possess in these respects may serve in some degree to outweigh the disadvantage of my inexperience in the art of literary presentation in this field.

But whether or not the choice of a biographer has been wisely made, it was at any rate a wise decision not to postpone too long the interval between the death of the subject of the biography and the collection and recording of the factual data which must form the foundation for a story of his life.

The apocryphal elements in the life‑histories of many famous men warn us how soon in the absence of reliable temporary records, many things we would wish to know concerning their lives are either irrecoverably lost, incrusted with the lore of legendary fiction or shrouded in the mists of myth. How soon too, does the opportunity pass for the biographer to secure from the relatives, friends and acquaintances of one deceased, direct testimony concerning his personal characteristics, the circumstances of his daily life and all the trivial yet nevertheless significant actions and events without knowledge of which he can at best prepare a mere factual record devoid of the human appeal and living semblance of a "flesh‑and‑blood" portraiture.

Already, in the case of Sir William Bragg, two only of his former colleagues on the staff of the University of Adelaide ‑ Sir William, Mitchell and Sir Douglas Mawson survive, and only two relatives by marriage ‑ Miss L.G. Todd and Mrs. Guy Fisher are now resident in Adelaide.

Sources of Information

His only, surviving son, William Lawrence (now Sir Lawrence) and his only daughter Gwendolen (Mrs. Alban Caroe) are resident in England. Sir Lawrence Bragg has been so kind as to send to me excerpts from an autobiographical statement of his father concerning his early life prior to coming to Australia.

Miss Lorna Todd has furnished me with a most interesting statement setting forth her reminiscences of Bragg's associations with her father, Sir Charles Todd and his family culminating in his marriage to her younger sister. Sir William Mitchell also has told me much concerning his colleague during his tenure of the Chair of Mathematics and Physics in Adelaide University. Sir John Madsen, who was Lecturer of Electrical Engineering in Adelaide during the last years of Bragg's term as Professor of Physics and who co‑operated with him in research work, still recalls clearly the conversation in which Bragg told him of the new point of view at which he had arrived regarding the nature of alpha‑rays, a point of view which subsequently led to a triumphal march of successes in experimental research. Others, whose acquaintance with him was of a more limited character such as that of student to teacher ‑ have contributed items of personal recollection.

My own opportunities of a close personal acquaintance with Bragg were unfortunately few, comprising only one brief meeting in Melbourne shortly prior to his departure to England; subsequently, occasional meetings and conversations during my visits to England in 1919, 1927 and 1931, and occasional correspondence.

Of literary sources available to me the most valuable as a record of his work and picture of his personality is the excellent obituary written by Professor Andrade of London University for the Royal Society of London.

A full appreciation of his scientific achievements could, of course, only be based upon a critical study and evaluation of ‑ the numerous papers contributed by him to the proceedings of scientific journals, or as set forth in the several books in which the contents of these were collected and integrated. It is neither my intention nor my prerogative to attempt more in these lectures towards such an appreciation than to endeavour to indicate the salient points in method and the main results of his researches. Sir Lawrence Bragg has informed me that it is his intention to write a full biography of his father and an account of his scientific work when in a few years time his retirement from office will afford him the leisure to undertake the task.

In the realm of popular exposition Bragg was an acknowledged master. Several lecture‑courses which he gave at the Royal Institution are published in book form. These also aid his biographer in his efforts to attain the difficult goal of "presenting a life‑work in full and significant delineation".

Heredity

William Henry Bragg was the son of Robert Henry Bragg who, at the early age of 25, gave up a post in the British Merchant Navy to purchase and cultivate a farm in the village of Westward near the town of Wigton in Cumberland. His mother, Mary Wood, was the daughter of the Vicar of the parish.

There seems to be little evidence to permit of a decision on the controversial and invidious question as to whether the son owed his outstanding intelligence to his father or to his mother. Moreover, in the light of the science genetics, the question is over‑simplified, the grand‑parents and even

remoter progenitors are claimants also to whatever congenital merit or demerit is assigned to any one of their descendants.

Heredity, despite the mathematical regularities which the work of Mendel and his successors have revealed in its operation, can play strange tricks. The appearance in their off‑spring of characteristics which neither parent is eager to claim as his (or her) donation ‑ I have been told ‑ a not infrequent source of marital altercation; the occasional Emergence of individuals of exceptional ability from a line of undistinguished ancestry (such illustrious names as those of Newton, Faraday and Einstein immediately occur to a physicist) may seem even more inexplicable.

On the other hand there is abundant evidence to show that, in common with other physical and mental characteristics, exceptional ability can and does descend from generation to generation. In England we have as illustrious instances of hereditary scientific genius the families of Darwin, of Herschel and of Huxley. There is already sufficient evidence to justify the addition of the name of Bragg in his honourable gallery.

The possession of exceptional scientific and mathematical ability is fully attested for two generations in the achievements of father (W.H.) and son (W.L.); less well known is the possession of distinctive artistic talent by the father (W.H.), his second son Robert (killed at Gallipoli) and his daughter Gwendolen (now Mrs. Alban Caroe). I learn from Miss Todd that the genes of genius have persisted into a third generation. Sir Lawrence Bragg's eldest son has had a distinguished scholastic career in mathematics at Rugby and at Cambridge, where, in succession which is probably unique, he is a Scholar of Trinity. In the second son the gene of artistic ability is again strongly dominant.

Childhood and Early Education

Both Bragg I s parents died young ‑ his mother when he was only seven ‑ and the responsibility of providing him with a home and education was willingly accepted by an uncle, William Bragg, who lived in the town of Market Harborough in Leicestershire, and had played a part in the re‑establishment of the local grammar school.

In some notes written by himself at the age of 70 concerning his early life, which I owe to the courtesy of Sir Lawrence, Bragg has given an interesting account of his experience at this school. It was not a very large one. " I was one of the six boys", he said "with which it opened. At the end of the first year I was given a scholarship exempting me from payment of fees. At the prize-giving ‑ there were many more than six boys at that time ‑ my name was called out and I went up to the desk to get the scholarship, not knowing what it was. I was puzzled and disappointed to go back empty‑handed."

The precocity which is a common if not an invariable indication of future genius, was not lacking in the school‑boy Bragg. At the early age of eleven he entered for and passed in the "Oxford Junior Locals", the youngest boy in England to get through.

His home life during this period, despite the care and affection bestowed upon him, was perhaps unfortunate in respect of the narrow religious atmosphere which prevailed, with its insistence on an unquestioning acceptance of prevalent orthodox beliefs.

At the age of 13, having probably reached the limit of the school's capacity to go further, his uncle sent him to King William's College in the Isle of Man. Here he rapidly developed a proficiency in his studies ‑ and especially in mathematics ‑ on the one hand and in school sports on the other.

This latter accomplishment was fortunate, for he confesses to having been a shy and retiring boy ‑ though it seems likely that this may have been due mainly to the fact that he was younger than his classmates ‑ and to excel in games was probably then, as now, a school boy's surest passport to popularity with his fellows. He rose, at any rate, to be Head of the school. In 1880 he entered for the examination for Scholarships at Trinity College, Cambridge, and was awarded one, but on advice of the authorities, delayed his entrance for a year.

It was in this year, at the age of 18 ‑ a critical period in the emotional life of an adolescent ‑ that the school he attended was, in Andrade's words, "swept by a storm of religious emotionalism" in which Bragg by reason of the revolt of his reason and sympathy against the irrational and inhuman dogmas of Athanasian theology, was involved so deeply as to recede rather than to progress in his studies and failed at the next scholarship examination to equal his previous performance. Nevertheless, he was awarded a minor scholarship and entered Trinity College, Cambridge University in 1881

In this new environment where ‑ unless the social and intellectual climate of Cambridge was very different then from what it is today ‑ at atmosphere of spiritual freedom and intellectual tolerance envelops the formalities of religious observance and the dogmas of theology this brief unhappy interlude of religious melancholia could not endure, and the young Bragg entered upon a new life full of interest and enjoyment.

He now lived and worked as a student in Trinity College he has told in his own words, written in 1927.

" I went up to Cambridge in 1881, taking the rather unusual course of beginning work there in the Long: I suppose I was in Cambridge six weeks or so, July and part of August. But I forget the exact date. I had rooms in master's Court. I appreciated thoroughly the beauty of the whole place; and I liked going to Routh's classes. It was lonely, because I was doing the unusual thing: and I had no companions. But it was good all the same. As a scholar of the College I went up every Long afterwards: it was always a jolly time. Very few restrictions: just the regular classes three times a week with Routh, and the preparation for them. After that tennis in plenty: boating on the river above Cambridge, and the summer weather, and Cambridge looking its best. I tried during that preliminary long to get through an exam that would excuse me the Littlego: and I failed in Latin, which seems to me now to be very odd, as I had studied Latin from the time I was seven and given a lot of schooling time to it, and worked conscientiously too! I had to take the Littlego, in November after all.

Cambridge gave me a good time, of course: although I might have done mach better if I had known more or been more easily sociable. I ought to have gone to lectures on other subjects than mathematics, and taken an interest in other things. It simply did not occur to me. I could not afford, or thought I could not afford, to join the Union or the Boating Club: which cut of f a good many opportunities. I had none of those experiences of discussion of the world and its problems with other young men, which many men seem to look back upon with so much pleasure. I worked at the mathematics all the morning, from about 5‑7 in the afternoon and an hour or so every evening, and then bed fairly early. Every

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afternoon I played a game, generally tennis, or went for a walk: my tennis was fairly good, so that I always found people ready to play."

There is an omission of a sentence or two in this except which can be made good from Andrade's obituary; it refers to the congratulations received from friends on his success in the Tripos examination. One of these was A.N. Whitehead, later of world‑wide reputation as a mathematician (he offered a derivation of the principle of relativity alternative to Einstein's) and philosopher (he is now Professor of Philosophy at Harvard) "who came and shook me by the hand saying 'may a fourth wrangler congratulate a third."' He had been fourth the year before.

After his crowning success, Bragg continued his mathematical studies and sat for the more advanced examination, Part III of the Tripos, as it then was. of the result of this he says, humorously, "I believe that none of us did too well, but nearly all got Firsts because the Senior Wrangler did not do any better than we did and they could not give him a second."

APPOINTMENT TO THE ADELAIDE CHAIR

Bragg, in his reminiscences, tells the story of how he came to apply for and be appointed to a Professorship in the University of Adelaide. In 1885 the Chair of Mathematics and Physics had been rendered vacant by the resignation of Professor Horace Lamb, who was the first occupant at the date when the University was established in 1874 and who now wished to return to England, where he had been offered the Chair of Pure Mathematics in the Owens College, Manchester. According to a practice still customary, the vacancy was advertised in the English press. Bragg had seen the advertisement but had not though of applying, believing that his youth (he was only 23) and entire lack of teaching experience would make his chance of appointment negligible. However, on his way to a lecture by J.J. Thomas (afterwards famous for his discoveries in the realm of atomic physics) he was joined by the lecturer, with whom he also had social acquaintance. The conversation turn on the Adelaide Chair. As a result of Thomson's advice Bragg telegraphed an application ‑ it was the last day of entry.

There were only a few applicants and Bragg was one of the three on the “short list" selected for interview. The interviewers were Professor Lamb, J.J. Thomson, and the Agent-General for South Australia, Sir Arthur Blyth. They also called in, to assist them in making a final choice, an Adelaide man who happened to be in London at the time. He was Mr. (afterwards Sir) Charles Todd who certainly did not know then that he was helping to bring to Australia not merely a professor but his own future son-in-law.

Another applicant much senior to Bragg was a Senior Wrangler of great ability whose claim to preference was, however, discounted by, his partiality for the contents of the bottle which, if it sometimes cheers, too often inebriates. So the choice fell upon Bragg, to whom it was first conveyed by a telegram from Australia that same evening, worded "As new professor of Mathematics and Physics in Adelaide University would you give some particulars of your career." Bragg's delight in an appointment which offered him, in his own words, "an assured position, a salary beyond all expectation (£800 a year), a new country with all the adventure of going abroad to it, and a breakaway from being a subject, to be now my own master" was tempered by the distress which the prospect of losing him caused to his worthy and benevolent old uncle to whom he was evidently as dear as a son, a distress, however, relieved by pride in "his nephew the professor".

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Fifty years later Bragg could still recall and record the enthusiasm and excitement of the preparations for departure: the novel experiences of the voyage to Australia in the largest vessel of the P. & 0. fleet ‑ the "Rome" of 4,500 tons ‑ and his efforts to learn something about physics (for his studies at Cambridge had been confined to Mathematics alone) during the voyage by reading Deschanel's Electricity and Magnetism!

Long years afterwards, when I paid him a visit in London and congratulated him on his appointment as Fullerian Professor of Chemistry in the Royal Institution, he said with humorous enjoyment: "The joke of it is that I always seem to be appointed as professor in subjects about which I know nothing." It was true, no doubt, that when he went to Adelaide he knew little or nothing of the formal physics of the text book; possibly true that when he took the Fullerian Chair of Chemistry not much more of text‑book Chemistry. But these deficiencies of academic knowledge had the advantage of leaving him with a clean sheet on which to write his own self‑acquired knowledge on these subjects and, as one of his most distinguished disciples (Dr. W.T. Astbury) says: "He had the most amazing faculty of taking up a subject on which he had only the foggiest ideas to begin with and quickly improving it out of all recognition."

From the first day of his arrival Bragg thoroughly enjoyed his life in Australia. He was fortunate in that the acquaintance already made in London with Charles Todd ‑ who was Director of the Adelaide Observatory ‑ immediately opened to him the door of a delightful domestic circle comprising in addition to the father and mother, three daughters and two sons. Very soon he, with a new friend, the late Dr. Alfred Lendon, became a regular Sunday afternoon and evening visitor at the Observatory home. “We were a cheerful party there," writes Miss Lorna Todd (who was eight years old at the time). "Fierce arguments over religious and social subjects were the order of the day amongst the men. The irresponsible and illogical chatter of my sisters" (thus irreverently did this child of eight characterise the conversation of her older sisters) "delighted him most. It was a revelation to a young man who had been taught to weigh every word he uttered, and he blossomed under the cheerful and inconsequent atmosphere."

A very natural and happy sequel to this idyll of domesticity was the marriage in the year 1889 of William Henry Bragg to Gwendoline, third daughter of Sir Charles and Lady Todd.

Of this marriage there was issue to sons, the first, William Lawrence (now Sir Lawrence, Director of the Cavendish Laboratory); the second, Robert, who was killed in the Gallipoli misadventure of World War I, and one daughter Gwendolen (Gwendy) now Mrs. Alban Caroe of London.

Bragg, from the very first, was marked as a born teacher and lecturer. Professor Andrade says (quoting ‑ no doubt from hearsay ‑ some Adelaide source) that in his early days "he was one of the least impressive of lecturers." If there is any justification for all this disparagement it may rest either on his complete inexperience in the art of lecturing or in his disdain of the use of rhetoric in which one of his colleagues, himself a master of that "poison of sincerity" was wont to appraise the quality of another's oratory.

Students who, at a later date, attended his lectures have one and all agreed in crediting him with exceptional powers of lucid exposition, so much so, indeed, that they accuse him of having been able to invest his discourse on abstruse topics with an altogether delusive simplicity. His interest and influence in educational matters soon spread beyond the precincts of the University. The curriculum of the secondary schools in South Australia, as more or less in all Australian States, dominated then as it is now by the public

12.

examinations syllabus, and, in particular, by the subjects demanded for matriculation, was still modeled on that of English public schools with their almost exclusive emphasis on the ancient languages and mathematics. Any scientific subject, if grudgingly permitted an hour or two a week of the timetable, was taught largely as an exercise in memorisation of the text‑book with little or no appeal to observation, lecture‑demonstration or laboratory exercises by the student.

Bragg was not long in raising his voice in criticism of this defect and in pleading the claim of science to be regarded as an educational medium of high practical value.

At the commemoration address which he gave in December, 1889, he concedes, doubtfully, the claim that the classical system of education "may perhaps develop in the younger generation the capability of fulfilling duties in certain traditional ways," but, he continues, "it does not so train their minds that, having a knowledge of the tools that modern science provides and judgement as to what may be done with them they may strike out for themselves new kinds of Work and new methods of working."

In the same address and on subsequent occasions he strongly advocated the introduction of practical work in school physics. "Every year," he said, "I have answers from book‑taught candidates which show a practical ignorance of physics." To emphasise his views he relates an amusing story of a youth's answer to an oral examination to the question:

"What is the use of a compass?"

After much hesitation came the answer:

"To find the latitude and longitude."

on the examiner asking "Could you do it?" the examinee promptly replied: No, Sir, but YOU could."

So far as the schools went, his exhortation, if heeded at all, led only to the casual and perfunctory performance of an extremely elementary type of practical exercises in physics in one or two of the larger schools. But, in his own University classes, systematic practical courses were very soon established, he himself for many years acting as instructor with little or no junior assistance.

His scientific interest seems to have turned, immediately after the assumption of his duties, from mathematics to physics. Indeed the mathematics required for the Cambridge University examinations in those days was perhaps not of a type to inspire many to pursue it further. From the first he found particular pleasure in demonstrating, both to his students in the routine lecture‑courses, and in public lectures and conversaziones, the more novel and spectacular miracle of scientific discovery. In these latter his young wife's social talents proved an invaluable asset.

Success in presenting the results of scientific research to a popular audience, unacquainted for the most part with the basic facts and principles of the special science in question, demands from the lecturer not merely a thorough understanding of his subject but the ability to translate the technical terminology of science into the language of every‑day usage. In this art, Bragg was singularly gifted. In the light of the nature of his subsequent achievements it is interesting to note that in 1895 the subject of a course of extension

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lectures was "Radiation"; in 1896 "X‑rays"; in 1897 "Sound". Undoubtedly the task of preparing these lectures and the experience gained in the technique of experimental demonstration must have served to lay a solid foundation of knowledge and skill which stood him in good stead in his future researches in the fields of radio‑activity and X‑rays.

Bragg also followed with keen interest the news which reached Australia from time to time of the remarkable discoveries and developments which were at this time (1895 and onwards) taking place in Europe in these last‑named subjects and in wireless telegraphy.

But he did more than merely read about them and talk about them. He promptly set about reproducing them by his own efforts with the very slight amount of technical assistance and meagre stock of instruments and apparatus which his laboratory possessed. Especially was his interest aroused by the discovery of X‑rays by Professor Rontgen of the University of Wurzburg in 1895. Rontgen published his discovery in December, 1895; news of it reached Australia in a brief cable in January, 1896.

In common with Professors of Physics in other Australian Universities, Bragg was immediately stirred to find means to produce this new kind of "invisible light".

X‑rays are produced by the impact of an electron stream on any solid object and to realise this all that is essential is an evacuated glass bulb into which are hermetically sealed two metallic electrode, and a source of high tension electricity. The type of vacuum‑tube used by Rontgen when he made his immortal discovery, was first designed and constructed by Sir Wm. Crookes and employed by him in his researches on the passage of electricity through rarefied air; the high‑tension electricity was supplied by a Ruhmkorff induction‑coil. The meagre equipment of the physics laboratory in those days did not include a Crookes tube and to have imported one would have meant a delay of several months. Fortunately Bragg's laboratory assistant, Mr. A.L. Rogers, was skilled in the art of glass‑working and by Bragg's direction at once proceeded with the attempt to construct a small tube. In this he was ultimately successful, but before the first tube was satisfactorily completed a citizen of Adelaide, Mr. S. Barbour, returned from a visit to England bringing with him two Crookes tubes purchased from a British firm. With the co‑operation of Professor Bragg remarkably good radiographs were taken with these tubes.

Subsequently Mr. Rogers made and evacuated many tubes which were successfully employed in medical radiography.

Professor Bragg's eldest son, William Lawrence (now Sir Lawrence) was a child of five at the time of these experiments in which, nevertheless, he was on one occasion a participant. In his foreword to the publication of Messrs. Watson and Sons' book entitled "Salute to the X‑ray pioneers of Australia", Sir Lawrence writes: "I well remember my father's first experiments with X‑ray tubes, although I was only six years old at the time. I think I must have been amongst the first to be employed as a patient. I had smashed my elbow badly by a fall and was taken to a cellar in the University for the exposure. The flickering greenish light, crackling and smell of ozone were sufficiently terrifying to impress the incident deeply in a child's mind. When I think, however, of the early experiments, the interest which they aroused in medical men in Australia is not their chief significance to me! I see them as fore‑runners of my father's interest in the ionisation of gases leading to his experiments with X‑rays from radium and finally the experiments on the diffraction of X‑rays by matter which we carried out together."

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The letter "X" which Rontgen chose to designate this new type of radiation, had reference of course to his confessed ignorance of their true nature. (His tentative hypothesis: "Ought not the new rays to be ascribed to longitudinal vibrations in the ether?" was fallacious.) It was not until 1912 that the experiments of von Laue in Germany, confirmed and extended in the next year by the Braggs, father and son, definitely proved them to be essentially identical in character with ordinary light. But among the apparatus which Bragg left behind him in the Physics laboratory was a large prism made of pure sulphur. On the testimony of Sir Lawrence Bragg, quoted in the publication just referred to, this was made with the special object of testing whether a beam of X‑rays would be refracted in passing through this prism. If this recollection is correct it shows that the problem of elucidating the nature of X‑rays was already occupying the elder Bragg's attention many years before its final solution. (I am personally somewhat doubtful of the correctness of this opinion, recalling the answer given to my question by Professor R.W. Chapman who as a lecturer under Bragg was in a position to have first‑hand knowledge that the prism was used for experiments on the refraction of electric (Hertzian) waves.)

In the same year in which Rontgen discovered X‑rays a young Italian, Guglielmo Marconi, was experimenting in his home town of Bologna on the transmission of signals by means of wireless telegraphy. Coming to England (his mother was Irish) in 1896 he found encouragement, financial support and technical assistance from the British General Post Office, and we all know of the remarkable developments in wireless communication which followed. In 1898 Professor Bragg was granted a year's leave of absence to visit England with a commission to inquire into matters of educational interest. His contacts with many eminent men of science must have created an interest in this new method of communication, for soon after his return he began experimenting in wireless transmission, first within the University and then from a transmitting station in the Observatory grounds to Henley Beach ‑ a distance of about five miles. I quote from Miss Lorna Todd's lively account of this event: "I think I am right," she says, "in saying that the first wireless pole to be erected in Australia was in the Observatory grounds. A receiving pole was put up on the sand‑hills at Henley Beach. My brother‑in‑law did much experimental work there. One afternoon I remember that my father asked me to pack tea and drive down with him to Henley Beach, saying he would send a 'wireless' to say that we were coming. I felt a very 'doubting Thomas' as I packed a specially nice tea and tied paper around the blackened picnic billy‑can (there were no thermos flasks in those days). However, when we got within sight of the tall pole on the sand‑hill there was my brother‑in‑law waving his arms and his cap, as thrilled as any schoolboy that the message had come through. It seemed a miracle. Both he and my father were almost boyish in the delight and the fun of the discoveries then being made so rapidly in science."

FIRST ORIGINAL RESEARCH WORK IN ADELAIDE

It has been a matter of remark by some who have discussed or commented upon Bragg's scientific career that his entry into the arena of scientific research should have been so long delayed.

It was not, in fact, until he had attained the age of 46 and had occupied the Chair of mathematics and Physics in the University for 18 years that he published anything of a quality entitling it to be considered as an important contribution to existing knowledge.

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This long interval during which his genius for experimental research lay latent, is indeed an exception, though by no means a solitary one, to the general rule that creative imagination and scientific activity are at their highest in the spring‑time or early summer of life.

In Bragg's case there are plausible grounds of explanation for a seasonal retardation.

As already stated, his natural interests were those of the physicist, rather than of the "pure" mathematician, yet his whole academic experience previous to his election to the Adelaide Chair had lain exclusively in the former discipline. Thus before he could even glimpse the horizon which bounded the great sea of existing physical science at that date ‑ a horizon more‑over which was expanding so rapidly that it continually receded from the voyager pursuing it ‑ he had an immense leeway to make up.

It is, of course in that unknown land beyond the horizon that lies the realm of scientific discovery, the realm of "research".

But that word had 'not, half a century or earlier ago, even in scientific circles ‑and certainly not in the politics of University finance ‑ attained the portentous significance which to‑day entitled it to vie in blessedness with "Mesopotamia" of sacred utterance.

Research had not yet acquired the status of a professional business. Rather was it then regarded as a natural and unforced by‑product of academic employment and intellectual interest; subordinate, nevertheless, to the performance of the professor's contractual obligation to train his students in the discipline of his special science, and to serve the general public as an authority and consultant on whom reliance could be placed for trustworthy information or wise counsel in all matters relating to his particular province of expert knowledge. It was in such a light, doubtless, that Bragg would view the responsibilities of his post.

His teaching duties at the outset were not onerous ‑ there were in his first year only two students in the laboratory ‑ but he did not hesitate to enlarge them whenever he saw occasion and opportunity.

For the benefit of those who could not attend during the day ‑ mainly teachers in secondary schools ‑ he instituted night‑lectures and practical work, which he conducted.

Sir William Mitchell has told me of the surprise and pleasure which he felt when, on his arrival to occupy the chair of English in 1894, he found that a branch of the British Teachers' Guild in which he had been interested in Scotland had already been established by Bragg in Adelaide. The high esteem in which he was held by the teaching profession and the gratitude and affection which they felt towards him were publicly expressed in tributes paid to him at a Teachers' Conference held in July, 1908, shortly after his decision to accept the invitation from Leeds University had been announced.

It need not be denied that other and distracting human influences competed strongly with the "divine curiosity" which is the stimulus to the task of intellectual pursuits. Bragg was no indoor recluse; he was athletic in body as he was active in mind. He had a love for all healthy outdoor sports and pastimes and indulged his liking in actual participation. By his own account (already quoted) he played tennis well and no doubt, found in it pleasant opportunities of social recreation.

16.

He took up golf and became one of several devotees among his colleagues (Mitchell and Henderson were fellow‑practitioners of that Royal and Ancient game) and become so proficient that in the year 1907 he was beaten in the championship contest only on the last two holes of the course by Henderson. He introduced the Canadian game of lacrosse to South Australia and was for several years captain of the North Adelaide Lacrosse team.

To these athletic proclivites he added artistic talents of no man order. He sketched and painted in water colours with the hand and eye of a true artist. His wife shared with him this delightful talent ‑ her teacher, Mr. H.P. Gill, would speak of her as a "first‑class artist ruined by marriage". During holidays husband and wife would sometimes sketch or paint, in company, a scene that took their fancy.

Gifted with a good musical ear, he not only enjoyed music but was himself a competent performer on the flute, an accomplishment which, on the testimony of Professor Andrade, he still practiced in his later London years.

Possessor of a fine presence and of all the social graces, he was a popular guest at social functions and entertainments whether public or private.

Fortunate in a happy marriage, blessed with and devoted to a family of two sons and a daughter, it might well be thought that he would have found his life in Adelaide so full and satisfying as to exclude all thought or wish of change or adventure either in the world of reality or the world of ideas.

But underneath all the pleasant preoccupation and lighter interests of his life there smoldered the urge to creative intellectual effort, nourished by the news of one great discovery after another in physics, and awaiting only the moment of inspiration to break out in action. Neither was this period of latent activity wholly devoid of all contribution to science.

In 1891 he contributed a paper to the Proceedings of the A. & N.Z.A.A.S. entitled "The elastic medium method of treating electrostatic theorems" and, as a sequel to this, in the following year another on "The energy of the electrostatic field", published in the Transactions of the Royal Society of South Australia. This latter he amplified and presented again at the Brisbane meting of the Association in 1895.

These papers are all in the true Faraday‑Maxwell tradition, in which the mathematical theory of electric and magnetic fields is based on analogy with the state of an elastic medium under stress.

They were essays in mathematical physics which put known results in a new light, ingenious variations on well‑established theory, but they contained no result of importance previously unknown, and they neither reported nor suggested new lines of experimental research.

The occasion initiatory to such suggestion came with the duty of preparing the presidential address to Section A of the A. & N.Z.A.A.S. at the Dunedin meeting of the Association in 1904.

It is a recognised duty of sectional presidents to present to their section a resume of important recent advances in some branch of their special science. This was a time when new and surprising discoveries were revolutionising basic ideas in regard to the nature of matter, of electricity and of radiation and the mutual relations of these entities to one another.

17.

Rontgen in 1895 had discovered X‑rays; J.J. Thomson, in 1897, had experimentally proved the existence of a universal type of electrical sub‑atom or corpuscle (now called the electron); Max Planck of Berlin had shown that light is radiated from atoms only in wave‑pulses carrying energy quanta proportionate in amount to the frequency of the waves. Einstein, in the same year in which he published his epoch‑making paper proving the relative character of space-extension and of time‑duration had also suggested an atomic aspect in the nature of light as a explanation of its power to eject electrons from surfaces on which it fell. Niels Bohr of Copenhagen had successfully applied Planck's quantum theory to solve the riddle of atomic spectra; the Curies, man and wife, following upon Henri Becquerel's discovery of the radio‑activity of the metal uranium, had isolated a new element, radium, a million times more active. Rutherford had analysed the radiation from radium and its products of disintegration and shown that it contained three entirely distinct kinds of rays ‑ which he called the alpha (a), beta (a) and gamma (y) rays.

Into this last, as yet only partially explored territory of the science of radioactivity now entered Bragg. It came about in this way.

He chose as the topic of his presidential address, "Some recent advances in the theory of ionisation".

Ionisation is a phenomenon which, as he states, "furnishes one of the principal methods by which the strange new properties of radioactive substances are made manifest and studied".

Neither air nor any other gas in its normal condition conducts the electric current. But, when irradiated by a beam of ultra‑violet light, or of X-rays, or of any of the three kinds of radiation emitted by radioactive substances, or when traversed by fast‑moving electrons, a small fraction of the molecules of a gas normally uncharged or neutral may acquire either a positive or a negative charge by losing or gaining one or more electrons. These electrically charged molecules are termed "ions", the gas is said to be "ionised" or in a state of "ionisation", and if a voltage difference is applied between two rods or plates of metal immersed in the gas, the ions drift under the influence of the electric force towards one or the other, thus effecting the transfer of electricity which constitutes an electric current.

Already in 1904 a vast amount of experimental work had been carried out by scientists in investigating the nature and properties of ions, the laws of the ionisation‑current and the properties of the various kinds of ionising agencies, in particular, the so‑called alpha, beta and gamma rays of radium. and other radioactive substances

Bragg made a critical examination of the information thus available on the penetrating and ionising powers of these three kinds of radiation (alternatively, of the absorption which they undergo in passing through matter) . He came to the conclusion that there was a radical difference in these respects between the alpha rays and the other two, concluding that whereas the main reason for the reduction in intensity and ultimate extinction of a beam of beta‑rays in passing through matter lay in the scattering of its moving electrons due to the repulsive forces exerted upon them by the fixed electrons of the atoms through which they passed, the alpha rays, by reason of their being nearly 2000 times as massive as an electron, suffered little or no such deviation from this cause and thus pursued a straight path until their initial velocity and energy were exhausted by the work done in ionising ‑ or at least "exciting" ‑ atoms through which they passed.