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BIOGRAPHICAL MEMOIRS

John Conrad Jaeger 1907-1979

Introduction Family background Early life and schooling; Sydney University The Cambridge years First marriage Tasmania Carslaw and Jaeger The war years Back to Tasmania: Books Second marriage Canberra and geophysics Personal research at ANU Retirement Personal qualities Conclusion Acknowledgements

By M.S. Paterson

This memoir was originally published in Historical Records of Australian Science, vol.5, no.3, 1982.

Introduction

John Conrad Jaeger was born in Sydney on 30th July, 1907. He lived most of his life in Australia and died in Canberra on 15th May 1979 at the age of 71. He had been a Fellow of the Australian Academy of Science since 1954, being among the group first elected after the foundation of the Academy. He was a member of Council of the Academy in 1957-1959 and Vice-President 1958-1959. In 1970 he was elected a Fellow of the Royal Society. His career was a full one and his interests diverse. However, he was a reticent person in many respects, especially in regard to his personal life and background. Therefore, while the following account will attempt to present the main features of his life, work and personality, some aspects will necessarily be more sketchy than others.

Family background

The Jaeger parental line appears to have originated in Germany. John Jaeger's father, Carl Jaeger, was born in Frankfurt-am-Main in 1869 or 1870; one account says that Carl's parents were visiting relatives in Germany at the time. It is not clear where Carl Jaeger grew up but as a young man he lived in South Africa and fought in the Boer war on the British side. Also it was in Johannesburg that he married Christine Louisa Sladden on 7th November 1905. Carl and Christine Louisa then moved to Sydney where Carl set up as a cigar manufacturer. I have very little information on Carl Jaeger's later life. John Jaeger rarely mentioned his father. However, I have been told of him giving recollections of his father's cigar factory and of the sight of girls rolling cigars on their thighs.

John Jaeger's mother and her family figured much more prominently in his early life and subsequent family contacts. His maternal grandfather was John Spiers Sladden, who came from a Kentish family. John Spiers Sladden ran a private school in Stockton-on-Tees, County Durham, and married Margaret Hannah Martin of that town. They had nine children, of whom John Jaeger's mother, Christine Louisa, was the seventh, born in 1869 or 1870. The first three children were Arthur, Frank and Harry, all of whom became engineers. Arthur Sladden remained in County Durham, living in Norton-on-Tees. John Jaeger spent many holidays in Arthur's household during his time in Cambridge. Miss Margaret Sladden, the second of Arthur's eight children, born in 1896 and still living in the district, has generously given me much of the information about the Sladden family recorded here. Arthur's brother, Harry Sladden, went to South Africa around 1898 and was manager of one of the earliest gold mines in Johannesburg before 1900, after which he started the firm of Sladden and Milne, engineers and importers. His sister Christine Louisa is said to have gone to South Africa for reasons of health, and it was presumably there that she first met Carl Jaeger whom she married. Also Carl Jaeger's sister, Elizabeth, described by Margaret Sladden as the most handsome woman she ever met, married Harry Sladden, thus making a double alliance between the two families. Although the latter marriage was later dissolved, it had as issue a daughter, Doris Sladden, John Jaeger's cousin. She married W.W. Gallie, who took over control of the Sladden and Milne firm after Harry Sladden's death in 1940, and she was frequently visited by John Jaeger in Johannesburg in later years. He is said to have felt very close to her, regarding her almost as a sister. Thus it is seen that the South African connection was an important one in John Jaeger's life, as well as the connection with his mother's family in the Stockton-on-Tees district.

Early life and schooling; Sydney University

John Jaeger was born in Sydney and was an only child. His parents were both aged 37 when he was born and one imagines much attention being lavished on him in his childhood. It is said that even in later years his mother fussed over him a great deal when he visited her. Little is known about the home environment of his childhood although it seems to have been a cultured one. The young Jaeger was at that time known as Conrad, a name which his mother retained for him throughout her life although in later years he became known generally as John, or sometimes Jack, except that to most of his junior colleagues he was 'The Prof'. (Also the German pronunciation of the surname was used in his youth, including in his undergraduate years in Sydney, but after returning from Cambridge he insisted on the English pronunciation).

In 1912, when he was five, John was taken by his parents on a visit to England where they stayed for some time with the Sladden relatives. Margaret Sladden has written the following recollection of John at this time: 'He was an exceptionally bright youngster. At the age of 5 he was interested in any engine; many he knew by name. My father, Arthur Sladden, was secretary of the South Durham Steel and Iron Works; when he realized how interested John was in the Works and engines he gave him one of the South Durham Steel and Iron Works Annual reports, with many photos as well as all the details. The youngster could read and understand a great deal of what he read and asked the most intelligent questions. He knew the various parts of the engines and where they should be placed.' And of John's parents at this time: 'John's mother was charming, like all my father's sisters and brothers well versed in the classics, Greek and Latin. I remember her well when they all came over to England in 1912. She was artistic and full of fun. So was uncle Carl Jaeger, a handsome man.'

Where John was born his parents were living in the inner western suburb of Stanmore in Sydney but they seem to have soon moved to the northern suburbs where John spent his formative school years (his mother lived in Chatswood in later years). He was evidently a very precocious student, taking his Qualifying Certificate at Altham College, Wahroonga, in 1917 at the age of 10, and his Intermediate Certificate at Wahroonga Grammar School in 1919 at the age of 12. After another year, he entered Sydney Church of England Grammar School in February 1921 on a scholarship and spent three years there, where he is recalled as 'a very distinguished scholar'. He was dux of the school in 1923 and during his period there gained an extraordinary number of prizes in subjects ranging from mechanical drawing, through English, mathematics and physics, to divinity. The present headmaster of SCEGS writes that 'apparently he was not a top class games player or the Registrar would have recorded his prowess in this area'. To my knowledge, he was never much interested in organized sport but his very early interests in engineering mentioned previously seem to have persisted during his school days. In the family collection there are photographs dated September 1923 of the erection of a wireless mast, indicating an interest in the early days of radio, and in his private study in later years he had a model steam engine which I believe he made himself in his youth; there is also a 1923 photograph of him in uniform, with a rifle, suggesting that he belonged to a school cadet corps.

In 1924, at the age of 16, John Jaeger entered Sydney University where he was to have a brilliant record. He was enrolled in the Faculty of Engineering during 1924 and 1925, achieving high distinctions in most of his subjects and being awarded the principal prizes and scholarships in physics and mathematics, including the Barker Scholarship No. 1 for Mathematics II. In 1926, he changed to the Faculty of Science, probably already as a result of the influence of Professor H.S. Carslaw, the professor of mathematics, who subsequently played an important role in his life. He continued his studies in mathematics and physics for another two years, being awarded first class honours and the University Medal in Mathematics in 1926 and first class honours and the University Medal in Physics in 1927, jointly for which the degree of Bachelor of Science was conferred on him in April 1928. He was also awarded the Barker Graduate Scholarship which was to take him to Cambridge. In the course of his studies in physics, he carried out experimental research under Professor V.A. Bailey on the motion of electrons in pentane which led to his first publication.' He also demonstrated in physics in the latter part of his period at Sydney University; a student of that time, Dr Germaine A. Joplin, remembers him as tall, slim and 'terribly shy', especially with the women students.

The Cambridge years

Jaeger, now 21, travelled to England in 1928 for further mathematical studies at Cambridge University, where he entered Trinity College. In Cambridge he studied for two years for the Mathematical Tripos. In Michaelmas Term 1928 he was listed at Trinity College as a 'Dominion and Colonial Exhibitioner' but in 1929 he was elected to a Senior Scholarship and was awarded a Walker Prize in 1930. He completed Part II of the Mathematical Tripos in 1930, being listed as Wrangler (Class I) with special distinction in subjects in Schedule B (b*) and awarded the Mayhew prize for proficiency in Applied Mathematics. The b* evidently gave Carslaw great satisfaction because several contemporaries have mentioned to me his elation in Sydney on receiving the news of it.

After his Tripos success, Jaeger stayed on in Cambridge to do research in theoretical physics, although at some time in the year following his completion of the Tripos he is said to have had a visit back to Australia. In 1931 he was elected to a Research Scholarship at Trinity College. In 1933 he was a candidate for a Research Fellowship at Trinity College but was unsuccessful, losing out to S. Chandrasekhar, the celebrated astrophysicist. Jaeger never took out a PhD degree, although the competition for the Research Fellowship required the submission of a thesis describing original research. He took out an MA in 1934 but in Cambridge this does not require further academic examinations.

Jaeger's research at this time, under R.H. Fowler, seems to have been mainly on the theory of metals, in particular the photoelectric effect, but he was also involved with research on the propagation of electromagnetic waves in ionized media and on circuit theory. It was evidently, on the whole, rather unsuccessful. In references, Fowler speculates that there was a 'lack of drive' or possibly 'bad luck' and Carslaw that 'he has perhaps suffered by the eagerness with which he has followed modern work in many fields'. However, Jaeger stayed on and his last two years in Cambridge, 1934 and 1935, under grants from the Royal Society and DSIR, were more successful. Fowler describes him as then having been 'most industrious and cheerful'. He worked in part as an assistant to Fowler but also to some extent independently and in collaboration with H.R. Hulme, and a number of publications resulted on interactions amongst electrons and positrons. Fowler describes the work as 'computing work of a nature far removed from "routine" [which] could only be undertaken by an accomplished mathematician...able to face laborious calculations with equanimity'.

In describing his Cambridge work when seeking appointment in the University of Tasmania, Jaeger wrote that, while his research there had been almost entirely in quantum mechanics, he had also read extensively in both pure and applied mathematics, in the latter chiefly in hydrodynamics and elasticity and in the former in differential and integral equation theory, analysis and the theory of Bessel and general hypergeometric functions. He pointed out that it was in the application of these branches of pure mathematics to problems of applied mathematics that his chief interest lay. He had already acted as a supervisor in mathematics at Emmanuel College for three years from about 1931 to 1934 which would have helped to sustain these mathematical interests.

Regarding his more general interests at this time I have very little information. One contemporary, Sir Mark Oliphant, remembers him as a 'loner' and another, Dr E.G. Bowen, as 'very shy', although he was known amongst the Cambridge-London Australian fraternity in the early thirties. He seems to have had an interest in archaeology, including that of Sutton Hoo. There also exists a lengthy description, in his hand, of a journey in the Middle East which encompassed such places as Baghdad, Damascus, Aleppo and Istanbul, as well as Bulgaria and Yugoslavia; and he made other visits to Europe. In later years he mentioned from time to time his vacation visits to his mother's relatives in Stockton-on-Tees, which he enjoyed very much during his Cambridge years; thus I have heard him speak of old customs surviving in that part of the country, such as beer for breakfast, and he obviously found the family environment congenial.

First marriage

Before leaving England for the Tasmanian post, Jaeger was married to Sylvia Percival Rees. The marriage took place in St. John's Church, Notting Hill, London on 23rd December 1935 and the newly-wed couple left the same day for Australia. Sylvia's address was given as a London one but it has been suggested that she originally came from the north country of England. The marriage did not turn out to be very successful in the long term and it is now difficult to learn much about it. Jaeger is recalled by one acquaintenance as having said of Sylvia that she 'insisted on marrying' him and as having remarked that he 'married her in a peasoup fog; it was a great mistake'. To my knowledge Jaeger never spoke about his first wife in later years and some of his Canberra colleagues were unaware of the earlier marriage. He did not even list it in his 'Who's Who in Australia' entry, although it was listed later in the British 'Who's Who'. There seem to have been no children of the marriage.

Early acquaintances in Hobart remember Sylvia as being 'very nice' and 'very pretty' but 'of a different world' and 'out of place in academic circles', 'more interested in ballroom dancing'. It is recalled that she kept a dog (Jaeger's passion was for cats). She lived with Jaeger for a time in Hobart but seems to have returned to England some time in the later thirties, coming back to Tasmania again when World War II broke out. It is not clear where she lived during the war but, judging from remarks in Carslaw's letters to Jaeger about 'the Lady Sylvia', she was involved in the Land Army in Tasmania and later lived for some time with Jaeger in Sydney during his period there in the wartime. She evidently returned to England again after the war and divorce proceedings were completed in 1950 following Jaeger's study leave in England in 1949.

Tasmania

In August 1935, Jaeger applied for a post as lecturer in mathematics at the University of Tasmania. His mathematical interests motivating this step have already been mentioned but it would seem also to have been influenced by the attraction of Tasmania itself. He had had a three-day sojourn in Hobart while en route to England in 1928 and, as he wrote when accepting the appointment, he had thought it 'one of the most delightful places in Australia'. In choosing to go to such a small university there may also have been an element of reaction to his Cambridge experience but it must be remembered as well that jobs were scarce in the mid-thirties. In December Jaeger received a cable confirming the appointment and he and Sylvia set out late that month for Australia, sailing in S.S. Moldavia from Marseille to Burnie in order to take up the appointment by February 15, 1936.

Thus in Hobart in 1936 Jaeger joined Professor E.J.G. Pitman to make up the staff of two who constituted the whole Mathematics Department of the University of Tasmania until the post-war years. Jaeger's arrival in Hobart also began a close association with Tasmania which continued, despite the later years away in Sydney and Canberra, for the rest of his life.

The Jaegers at first lived next door to the Pitmans in Davey Street, Hobart, and shared social life with them, including games of tennis. However, the relationship between Pitman and Jaeger never became a close one, even though they shared the same office until the post-war years. Each spent such time at the university as was necessary for teaching or administration but otherwise generally worked at home, and there was very little communication between them about their own researches. Pitman recalls that 'they got on well by not worrying each other' and that he was even unaware that Jaeger was writing a book at one time when he was working on one. To their contemporaries the relations between Pitman and Jaeger appeared to be rather distant, especially in Jaeger's later years at University of Tasmania, but the two men had a high professional respect for each other and remained in touch after Jaeger moved to Canberra, where on at least one occasion Pitman stayed with Jaeger when visiting there, and there were other contacts.

In the pre-war years, Pitman and Jaeger shared the whole teaching of both pure and applied mathematics and complemented each other very well. Pitman recalls that they each gave some 16 lectures per week. Jaeger enjoyed teaching and his lectures were popular. Although he mainly taught applied mathematics in the advanced years, he gave the lectures in first year pure mathematics. However, he regarded the latter very much as pure mathematics for engineers and presented it with the aid of many examples. As will be remarked upon further later, he is remembered by his former students as an excellent lecturer and teacher.

After settling down in Hobart, Jaeger continued with some of his interests in quantum mechanics and published a few short notes and papers following up his Cambridge work, but he stated at the time of his appointment to a chair in 1950 that his work was pursued 'with difficulty and much of it was never published because of the war'. However, after returning to Australia, Jaeger's links with Carslaw, although never broken during the Cambridge years, became closer and there began the famous collaboration on operational methods in applied mathematics and on the mathematical theory of the conduction of heat. Beginning with a joint paper with Carslaw in 1938, a remarkable upsurge in Jaeger's output occurred, setting a pattern for the remainder of his career. We must therefore now consider the connection with Carslaw more closely.

Carslaw and Jaeger

In an address at the 1975 celebration of the centenary of Carslaw's birth, Jaeger paid tribute to Carslaw in these words: 'I, of course, owe more than any other person to him. He was the ideal Mentor, human, kindly, knowledgeable about everything, interested in the problems and advancement of his students'. Clearly Carslaw was the most important figure in Jaeger's professional formation and would seem also to have been a powerful influence in the development of his personality.

Horatio Scott Carslaw (1870-1954), a Scot by birth, was educated in Glasgow and Cambridge, worked for a year under Sommerfeld in Göttingen, lectured in mathematics at Glasgow University for a few years, and became a Fellow of Emmanuel College, Cambridge, before being appointed to the Chair of Pure and Applied Mathematics in the University of Sydney in 1903. He held this post until retirement in 1935. He had married in 1907 but his wife died within a year of his marriage and he never remarried. One can speculate that his students became, in a projected sense, his family and the one to benefit most from this was John Jaeger, whose contact with Carslaw presumably began in his first year at the University of Sydney. In his obituary of Carslaw in The Australian Mathematics Teacher, Jaeger writes:

Carslaw's attitude to all students was one of combined kindness and firmness, so that one always knew precisely where one was. In my first and second years I was told that it was just possible that I had mathematical ability – I was not to get any exaggerated ideas about this, it was just possible, but only just – and certainly I would have to work a great deal harder than I was doing. At the end of third year, the prospect of a scholarship to Cambridge appeared, and with it the touch of the iron hand in the velvet glove: I must not complete my engineering course, but must do physics honours – engineering would spoil my mathematics.

In fourth year I learnt a little from Carslaw of the enormous amount of reading and experiment which goes into the understanding of any branch of rnathematics. He was working on the third edition of his Fourier's Series and in particular on the Appendix on the Lebesgue integral; for perhaps three months he worked through a treatment of L.C. Young's tract, and four times a week he would write out in front of me his treatment of various aspects of this. It was a wonderful education for an impatient youth who felt that he ought to be able to understand anything in a week or two.

In Cambridge like many other Australian students including many who were not mathematicians, I profited on two of his sabbatical leaves from his habit of taking us with him on motor tours as chauffeur-companions.... On these trips everything was settled – you drove to such and such a place, stayed in the right hotel, were supplied with the right books to read, and drove along to the accompaniment of a continuous series of random reminiscences of mathematics and things in general.

In later years this education in serene living was continued for many of us with visits to his home at Burradoo.... I was fortunate in enjoying working in the garden and the wood heap and was more valued as an axeman than as a mathematician. Everything went comfortably to rule....'

The active collaboration in mathematical research that began in the prewar years arose in the context of operational methods, a topic marked with controversy since the time of Heaviside. Jaeger writes that their collaboration dates from Carslaw's sending him a copy of a manuscript for criticism: 'Now I had been to Jeffrey's lectures and read his book and a good deal else on the subject but was never happy with it. I can still remember reading Carslaw's manuscript and everything suddenly appeared simple – this was the good treatment at last.... From this time, Carslaw and I collaborated extensively and soon decided to write our own book'. This was in about 1937 and eventually led to their joint book Operational Methods in Applied Mathematics, published in 1941 which 'was intended to show off the paces of the Carslaw method with the minimum of theory and the maximum number and range of examples. Carslaw was responsible for the "Pure" chapters and that on conduction of heat. He remarked that "the discerning reader" would be able to decide on the authorship of the various chapters by their literary style and, in particular, punctuation'.

From 1938 to 1941 Carslaw and Jaeger wrote a number of joint papers on the application of the Laplace transformation method, a particular operational method, to problems on the conduction of heat. This work represents the beginning of Jaeger's long-continued involvement with the conduction of heat, an involvement that he thus inherited from Carslaw whose publications on the topic date back to 1902. Concurrently with the Carslaw and Jaeger papers, Jaeger also wrote several papers on other applications of the Laplace transformation method. Jaeger's own work on the theory of the conduction of heat continued during the war years and for the remainder of his years in Tasmania with a series of papers on the solution of specific problems of practical interest, making extensive use of the Laplace transformation methods. In many of these papers numerical results were an important feature, again revealing Jaeger's skill and perseverance in computation using manual machines, although by now he had some assistance in this work.

In the later war years, the collaborative efforts of Carslaw and Jaeger tapered off, presumably due to failing health and advancing age on Carslaw's side and increasing involvement in wartime work on Jaeger's side. Thus, at the end of the war, when the task of preparing a new book based on Carslaw's Introduction to the Mathematical Theory of the Conduction of Heat in Solids (1921) was taken up in 1945, it was Jaeger who carried the main responsibility. In a letter written to 'My dear Jaeger' on 28 July 1945, Carslaw says 'I felt that K.S. [Sisam] should know that I am really only by courtesy one of the authors of Carslaw and Jaeger's Conduction of Heat.... It is true that it is to be a continuation of Carslaw's Conduction of Heat and in that sense it is fitting that my name remain with yours; but, as I have impressed on you, the work will really be yours.... I shall be happy to go through the finished script and to give my views on changes and so forth, when you ask for them. I am ever so glad that you have taken on the job and that my old work will live again, thanks to you'. The new Conduction of Heat was published in 1947. From 1948 Carslaw's eyesight began to fail, limiting his activities, and there seems to have been no further active mathematical collaboration with Jaeger up to Carslaw's death in November, 1954. In a letter to Jaeger on July 30, 1949, Carslaw responds to the receipt from Jaeger of a copy of his just-published An Introduction to the Laplace Transformation by saying 'I am greatly pleased with it and very much touched by the inscription J.C.J. to his Master H.S.C. Thank you very much for this and also for the joy work with you has given me always but most of all, since 1937 when our C and J co-operation started'.

The war years

In the perverse way in which war often enlarges opportunities for individuals, the Second World War years saw Jaeger involved in a number of projects of an applied nature which gave scope to his deeply-rooted interest in engineering, rather neglected since he was diverted at the University of Sydney into the direction of mathematics and physics. The practical projects and consulting connections that now arose were also to establish something of a pattern for the post-war years. In the earlier years of the war, the two main problems that he became involved in were, first, the production of charcoal and, second, the fracture of sandstone rollers used in newsprint production. Later he transferred to Sydney to work for the Council for Scientific and Industrial Research (CSIR, the predecessor of CSIRO) in applied theoretical work.

The scarcity of liquid fuels during the war years had led to the use of gas producers on motor vehicles, which required supplies of suitable charcoal. Research in this area had been initiated by Professor A.L. McAulay and others in the University of Tasmania in 1940 or earlier, before McAulay became involved in the well-known optical munitions work at the university, and laboratory space had been made available in the Physics Department. Jaeger's participation in the work around 1940-1941 was centred on the properties of the charcoal itself and their dependence on the methods of production. Apart from laboratory work at the university, the project also involved actual production of charcoal in pits in the country. Much of the latter work was done on 'Lottah', near Nubeena on the Tasman Peninsula, the family property of the Clarkes, where Patty Clarke, whom he was to marry later, had grown up. With the aid of Miss Cynthia M. Johnson (later Mrs Alexander) as laboratory assistant and a grant from the Tasmanian Technical Committee on Fuels, the work led to two publications, one on the ash content of charcoal from various Tasmanian timbers and the other, more sophisticated, on the internal temperatures attained during carbonization; he was able to show that control of the temperature history within the piece of wood through control of the size of the log and of the external temperature was vital in determining the size and friability of the pieces of charcoal produced, properties that are important in its use in gas producers. He also later did some work on methods of measuring the dust content in the gas.

When the Australian Newsprint Mills began operations in Boyer, Tasmania, in 1941, trouble was soon experienced with cracking of the grindstones used, which at that time were made of a natural sandstone. Through Professor A. Burn, professor of engineering at University of Tasmania, Jaeger was contacted by Mr J.L. Somerville, then chief chemist of the Mills, and asked to study the problem since it was thought to involve the effects of heat production in the grinding, a matter that had not previously been worried about in this connection. Jaeger's attack on the problem took two directions. On the one hand, he used the theory of the conduction of heat to calculate the temperature profile developed in the grindstone in operation and from this calculated the thermal stresses, and on the other hand he conducted experiments on the mechanical properties of sandstones under the water-saturated conditions (again with the aid of Miss Cynthia Johnson). Apart from any reports that may have been written for the company on this work, it stimulated a number of papers by Jaeger, both alone and in co-authorship with Somerville, on the general principles; there were three papers on the first aspect and one on the second. But perhaps the most interesting feature of this work lies in the way it reveals the effective combination of Jaeger the engineer singling out the essential elements of the problem and Jaeger the applied mathematician dealing with the theoretical questions posed. It may also be mentioned at this point that the interaction with Somerville and the Australian Newsprint Mills continued after the war, leading to a further paper on the calculation of the maximum temperature attained in the wood itself just prior to the removal from the log in the grinding process. This study involved both a macroscopic model and a discussion of the grinding process on the microscopic scale.

Concurrently with the applied work just mentioned, Jaeger managed to keep up as well a flow of mathematical papers on conduction of heat; and other topics as mentioned previously. In December 1941, he was admitted to the DSc degree by Sydney University for a thesis entitled 'A study of the mathematical theory of heat conduction', confirming his now considerable standing as an applied mathematician. At this point a new call was made upon him.

In October 1942, at the instigation of Dr F.W.G. (later Sir Frederick) White, head of the CSIR Radiophysics Laboratory in Sydney, the Vice-Chancellor of the University of Tasmania, Professor Miller, was approached by the chairman of CSIR, Sir David Rivett, requesting the full-time services of Jaeger at the Radiophysics Laboratory for the duration of the war, to engage in 'experimental and mathematical researches connected with the generation and propagation of radio waves'. Although this would leave the entire mathematics teaching load to Pitman, the request was agreed to and Jaeger took up duties in Sydney in about January, 1943.

At the Radiophysics Laboratory, the centre for radar research and development in Australia during the war, Jaeger was involved in a variety of theoretical problems. Sorne of these, such as the calculation of currents and potentials in electrical circuits, arose out of equipment design and development. However, Jaeger's main contributions were in the two areas of antenna patterns and radio wave propagation. He became involved in the wave propagation and absorption work initially through White, whose responsibilities for ionospheric prediction had come to include the problem of predicting the lowest usable high frequency for radio transmission above 2 MHz, a requirement of the armed services. Australia in the War of 1939-1945 (Series 4, Vol. 5, p. 540: Australian War Memorial, Canberra, 1958) also mentioned a 'mathematical group under Dr Jaeger' as being involved, with Pawsey's group, in a study of the anomalous propagation or superrefraction phenomenon (F.J. Kerr, Aust. J. Sci. Res. 1948, A1, 433), but I have found no evidence that Jaeger himself worked directly on this problem, and Sir Frederick White's recollection is that Jaeger worked as an individual at Radiophysics rather than as leader of a group. However, Jaeger did write two meteorological papers while at Radiophysics, which probably related to the climatological origins of the superrefraction problem since one of the processes identified as leading to superrefraction was the movement of nocturnally-cooled air out to sea. Thus Jaeger published one paper on the effect of wind on nocturnal cooling and also pursued this topic further after the war. The other paper, on diffusion in turbulent flow between parallel planes, is related but of wider application.

The following Radiophysics technical notes (T.I.) and reports (R.P.) were written in this period:

Another war-time problem in which Jaeger became involved soon after his transfer to Radiophysics was that of determining the temperature reached in the retina of the eye when looking into the sun. This problem had arisen because eye damage was being suffered by anti-aircraft gunners attempting to intercept dive bombers attacking from the direction of the sun, and it was being studied by Dr G.H. Briggs and collaborators of CSIR National Standards Laboratory, then in the same building as Radiophysics. Briggs arranged for Jaeger to make calculations on the heating of the retina under the solar radiation, taking into account the conduction of heat in the blood-filled tissue of the retina. The calculated temperatures were consistent with values measured in the eyes of rabbits and monkeys by J.C. Eccles and J. Flynn ( Medical J. Aust. 1944, 20, 339), working at the Kanematsu Institute in Sydney at the time. Special goggles were then designed by the CSIR scientists to give sufficient absorption of the visible and infrared radiation to avoid eye damage on looking into the sun ( Australia in the War of 1939-1945, Series 4, Vol. 5, pp. 271-2: Australian War Memorial, Canberra, 1958). Jaeger's calculations on the heating of the retina were not published but in a related paper somewhat later he refers to them.

During the period in Radiophysics, in spite of his involvement in the variety of problems just described, Jaeger managed in addition to continue some work on the theory of the conduction of heat and had several papers published, as well as the paper on thermal stresses arising out of his earlier work on sandstone rollers mentioned above, and a few short papers published after returning to Tasmania may be assigned to this period. A conspicuous feature of these papers and, indeed, of most of the theoretical studies that he undertook in this period, was the use of Laplace transformations in solving the differential equations concerned. It was therefore natural that he should be asked to give a course of lectures on the application of the Laplace transformation of the National Standards Laboratory in Sydney in 1944. These lectures were very well received and are still recalled clearly by people who attended them. They were published in a mimeographed edition by CSIR in 1946 and subsequently went through three editions with Methuen.

Back to Tasmania: Books

In September 1944, at Pitman's instigation, the University of Tasmania wrote to CSIR requesting that Jaeger be allowed to return to the university where he was badly needed because of the teaching load. His return was agreed to in October, although he does not appear to have actually made the move back to Hobart until April 1945. Meanwhile, in December 1944, the university raised his status from lecturer to senior lecturer, dating the change from July 1st, 1944.

Jaeger's post-war years in Tasmania saw a remarkable production of books. From 1946 to 1951 four books were published. One was a substantially augmented new edition of Operational methods in Applied Mathematics with Carslaw, and the other three were new books: Conduction of Heat in Solids with Carslaw; An Introduction to the Laplace Transformation and An Introduction to Applied Mathematics.

Conduction of Heat in Solids was written within a period of not more than a year, mainly by Jaeger himself as previously noted. Of course, a framework existed in Carslaw's earlier book, and some of the new material had already been worked through in the form of papers in previous years. However, to complete the book in this period was an impressive achievement. A considerable amount of new material was added in the 1959 edition, done entirely by Jaeger after Carslaw's death in 1954. This book represents a summing up of the work of both Jaeger and Carslaw on the mathematical theory of the conduction of heat in solids. It remains the classical source to this day and is the work through which Jaeger's name is most widely known.

An Introduction to the Laplace Transformation, published in 1959 as a Methuen Monograph, was essentially the same as the mimeographed edition of Jaeger's 1944 lectures already mentioned. It went through two further editions, the third being re-worked by G.H. Newstead.

The third book of this period, An Introduction to Applied Mathematics, published in 1951, was an entirely new book, derived from Jaeger's lectures at the University of Tasmania. It was completed during a sabbatical leave in 1949-1950. The Jaegerean philosophy underlying it was well expressed on the dust jacket as follows: 'This undergraduate textbook is concerned mainly with the means of applying mathematics (particularly differential equations) to the study of physical and engineering problems. It is intended as a course which is more interesting and useful to students of engineering and physics than those usually followed by specialist mathematicians but which is not inferior in developing mathematical technique'. It was sufficiently successful to be reprinted several times and a second edition was later prepared by A.M. Starfield.

At the beginning of 1948, the University of Tasmania was again approached by CSIR, this time with a request that Jaeger be allowed to work part-time with CSIR, visiting from time to time in vacations especially to the Division of Radiophysics. This was agreed to and led to Jaeger's involvement in several areas, including the propagation of radio waves in the solar corona, the nature of the moon's surface, and the design requirements for electronic computers.

In the post-war dramatic expansion in radioastronomy, radio emission from the sun came under close study. Jaeger, with experience already in problems of the propagation of radio waves in the earth's ionosphere, was drawn into this work by Dr E.G. Bowen, then chief of Radiophysics, who encouraged a collaboration with Dr K.C. Westfold. The first Jaeger and Westfold study was concerned with the production of transient oscillations resulting from a sudden disturbance in an ionized medium such as the sun's atmosphere. The second paper dealt with the propagation of radio waves through the sun's atmosphere, involving considerations very similar to those that Jaeger had applied to the earth's ionosphere in the war-time work and giving an explanation of the 'double-humped' profile of the observed solar noise bursts. Again, the application of the Laplace transformation method played an important part in the work.

Another extra-terrestrial problem that Jaeger became interested in at this time was that of the nature of the moon's surface. It was already known from the rate at which the thermal radiation from the moon's surface drops off during an eclipse that the thermal conductivity of the surface layers must be relatively low, and a similar observation applies to the variations from lunar 'day' to 'night' (the lunation or lunar month). J.H. Piddington and H.C. Minnett in 1949 extended these observations into the microwave range on the timescale of the lunation. Jaeger's entry into the subject seems to have been sparked off by a paper by A.J. Wesselink in 1948 on the calculation of the rate of cooling at the moon's surface during an eclipse or a lunation but he was able to use Piddington and Minnett's observations. In order to choose reasonable values for the thermal conductivity of a dust without air between the particles he approached Mr A.F.A. Harper at National Standards Laboratory, Sydney. This led to a joint paper in Nature by Jaeger and Harper in which they concluded that over most of the surface of the moon there was a layer of dust of only about 2mm thickness, overlying a granular layer similar to pumice or gravel; a more detailed analysis of the question was given later by Jaeger. The idea of a layer of dust on the moon's surface was not new (Wesselink and Piddington and Minnett had discussed it) but a new precision of analysis was introduced, permitting the conclusion that the layer was quite thin – a conclusion that became very significant some years later when the landing of spacecraft on the moon was being planned.

Mention has already been made of Jaeger's skill in computing. This led in the post-war years to his involvement in the two different directions in computing machine development. In these years, he had a small laboratory or workshop in the University of Tasmania, possibly the same as that which he earlier had the use of for the charcoal work. This enabled him to work on devices for analogue computation and for teaching demonstrations in his classes. The laboratory also became something of a gathering place for engineering students, some of whom assisted with the work there. One in particular, J.D. Clarke, assisted Jaeger in constructing several analogue machines. A joint paper with Clarke describes an integrating device using anti-aircraft predictor parts, and another paper describes a link mechanism made with Clarke's help. Also an eight-integrator mechanical differential analyser was developed. Professor D.R. Hartree evidently visited Jaeger at University of Tasmania around this time and would have helped to stimulate Jaeger's interests in computer developments. One of Jaeger's machines was used subsequently by Professor A.R. Oliver in the Engineering Department, but of course before long the advent of electronic digital computers displaced its use. In the latter connection, Dr T. Pearcey and collaborators during the post-war years were developing an electronic computer at Radiophysics (CSIRAC, one of the earliest such computers later moved to Melbourne). The concepts of a programme and of subroutines were being evolved and Pearcey recalls long conversations with Jaeger on the requirements of a computer and on what was necessary to perform a calculation, which affected the design and procedures of CSIRAC. There was even some discussion at one stage of setting up a mathematical division of CSIRO under Jaeger to include computing but it did not come to fruition.

During the year 1947, Jaeger received two distinguished medals, the Thomas Ranken Lyle Medal for Physics and Mathematics from the Australian National Research Council, and the Walter Burfitt Prize from the Royal Society of NSW. In 1948 he acted as professor of mathematics during Pitman's absence on sabbatical leave. Then he himself took sabbatical leave for about a year from mid-1949, probably with assistance from the British Council. I have found no record of where he spent this year but it seems that at least a substantial part of it was spent in Cambridge. The writing of the textbook on applied mathematics, mentioned earlier, was done during this time. Jaeger had been promoted to associate professor in January 1949 and was finally appointed Professor of Applied Mathematics from July 1950. This appointment, however, was to be short-lived and a year later he wrote his letter of resignation following appointment to a chair at the new Australian National University. Although he was obviously deeply attached to Tasmania one can infer from some remarks in Carslaw's letters to him that he had not felt altogether settled after the war and had been considering other posts: 'why do you say you will not get the St. John's Coll. Fellowship?' (H.S.C. to J.C.J., 23/3/48); discussion of whether there will be any openings at Sydney University, and reply to a request about a possible Fellowship at St. Andrew's (28/7/45). The ANU appointment was to initiate a new phase in his career.

Before leaving Jaeger's period at the University of Tasmania some remarks on his teaching of mathematics are appropriate. I have spoken with many people whom he taught there and he is invariably remembered for the clarity, the inspiration, and the relevance of his teaching in applied mathematics: 'one of the best lecturers there...kept attention and made it all real...really interested in examples...examples that were highly practical, which was appealing...exceptionally good teacher, very clear and good in communicating...very interested in students'. This good relationship with students arose at least in part out of his own driving interest in the practical application of mathematics. He particularly enjoyed the stimulus of teaching the engineering students and I have heard him remark regretfully a number of times during his period at ANU that he missed the teaching there. He has also said that he found the routine of teaching as something helpful for continuity when research was not going well. His practical outlook is well summarized in the introduction to his short paper on 'Demonstration apparatus in the teaching of applied mathematics': 'Although it is true that most students can visualize the behaviour of a mechanical system quite well from a proper description or a good drawing, I find that all students, and particularly engineers, seem to be greatly stimulated by an occasional demonstration related to their work. For some time I have been trying to construct courses in applied mathematics in which all the examples studied have obvious practical applications. This need not involve any lowering of the standard of the mathematical work...'.

Second marriage

Jaeger's friendship with Martha Elizabeth (Patty) Clarke began in his early years in Hobart and developed into his most important and enduring personal relationship. Patty was born in Tasmania in 1901 of an old Tasmanian family. Her grandfather, a Congregational parson, had married a daughter of Henry Hopkins, an early entrepreneur in Hobart, whose mansion 'Summerhome' came into Clarke ownership and later served as a gathering point for the Clarke families. Patty's father, George Clarke, owned a farm, known as 'Lottah', near Nubeena on the Tasman Peninsula, from which Patty used to travel by boat to school in Hobart in her childhood. She shared her strong attachment to this region with John Jaeger and it attracted them back there in retirement. In earlier years, during Jaeger's University of Tasmania time, Patty already owned a property known as 'Frogmore' deep in the bush near Lottah which she and John used for many years as a holiday retreat; stories are told of the primitiveness of life there and of the vicissitudes of transporting such things as furniture into its nearly inaccessible cottage.

Patty joined the staff of the University of Tasmania as a typist in 1927 and worked there until her resignation in 1950, being chief clerk from 1943 onwards. She was an attractive person, very well known within the university circles, and it was widely acknowledged that she effectively 'ran' the university during the war years when the Registrar was called up. Jaeger presumably knew her from soon after his arrival in Hobart. By 1943, acknowledgement is appearing in his papers of her assistance with computations, and she is a co-author in two papers on numerical results. The choice of Lottah for carrying out the charcoal work in the early war years also indicates a close friendship with Patty by this time. And many years later, in his Carslaw Oration, Jaeger recalls her assistance in typing around the same period; he attributed the fact that Carslaw's letters to him were 'so good' as being due to Patty 'who typed our books and my replies to him and, even in the difficult war years, supplied stationary'. In a letter in October 1942, Carslaw refers to 'your Private Secretary' and says 'You have been most fortunate in having so ardent and keen a worker and C.H. [ Conduction of Heat ] owes her a great deal'.

John and Patty were married in Hobart on October 24, 1950 almost immediately after the dissolution of his previous marriage was completed. Dr E.G. Bowen of CSIRO Division of Radiophysics, on a visit to Tasmania in connection with cloud-seeding experiments at the time, acted as 'best man' and arranged a suitable celebration. John Cruickshank, an engineering student at that time, also recalls a memorable party with John the previous night. John and Patty were at that time living in separate halves of an old house in Prospect Place, Hobart, which was well-known as the venue of parties and the meeting place of visitors and students. The house was also notable for its old furniture and machinery (a mangle is often mentioned), of which they were keen collectors. They lived on there until they moved to Canberra.

Patty brought to John a feeling of family and of connection with Tasmania that seems to have had deep meaning for him. He is remembered as liking to sit amongst the family in Summerhome, with plenty of children around, although his relationship with children was not a particularly easy one and he talked with them as adults. I have heard him remark several times in later years that he and Patty married too late in life to have children, as if he regretted it, but on other occasions he seemed somewhat intolerant of children. Patty was very devoted to him and used to work very hard for him. After their marriage, and during their years in Canberra, her energies were entirely directed to his welfare and the maintenance of their home at Oaks Estate, ACT; and he was very attached to her and became very dependent on her. Their interests in country-style living and in antiquarian pursuits were shared in a remarkable degree. They were also well known as generous drinkers and stories are told of the remarkable stamina of John on occasion in the company of colleagues.

Most of John and Patty's married years were spent in Canberra where they soon moved into 'The Oaks' in Oaks Estate, near Queanbeyan, a few kilometres from Canberra. This was a notable early Australian stone house, dating from about 1837, where they were able to develop the style of living congenial to their interests. Some internal modifications were made, largely by John himself, who enjoyed such activities as carpentry, and the house was furnished with very fine antique furniture, amongst which a four-poster bed is particularly memorable. The interest in furniture was perhaps stronger with Patty, while John indulged his passion for old machinery by accumulating a remarkable collection of steam engines and early farm machinery which was a source of much interest to visitors. Some of us of the earlier days of the University well remember the day when a newly acquired steam traction engine was driven under its own steam from Hall, through the suburbs of Canberra, to Oaks Estate, with John standing on the footboards supervising and Patty driving the utility behind with a load of fuel. Many visitors were entertained at The Oaks and Christmas parties were held for the entire department when it was still relatively small, with horse rides for the children. However, except in their first years in Canberra, John and Patty did not take a very active part in the social life in the University as a whole, and in later years they entertained less at home, becoming quite reclusive by the time of John's retirement.

Canberra and geophysics

The idea of including geophysics as one of the areas of research in physics in the proposed Australian National University was already discussed by an advisory committee early in 1946, possibly with atmospheric physics in mind, but they finally decided that the choice of areas should be left to the director of the research school. Geophysics does not figure in the proposals of Professor M.L.E. (later Sir Mark) Oliphant, advisor on physical sciences to the new university after its foundation and subsequently first Director of the Research School of Physical Sciences, until he took up residence in Canberra in August 1950. However, soon after this, Oliphant arranged for Professor J. Tuzo Wilson of the University of Toronto to lead a seminar at the university on September 25-26, 1950 on 'Geophysics: Earth Structure' under the auspices of the university's Visiting Scholar programme. Oliphant's interest in geophysics had arisen through contacts with E.C. (later Sir Edward) Bullard, then a professor in Toronto, whose enthusiasm for solid earth geophysics suggested a similar pursuit at ANU. In November 1950, Oliphant obtained from Tuzo Wilson a report on the aspects of geophysics most suitable for development in Canberra and he began moves to establish a department of geophysics in the School. Both D.F. Martyn and K.E. Bullen having indicated that they were not interested in starting geophysics at ANU, Oliphant approached Jaeger whom he had known from Cambridge days and whom he knew to have some interest in geophysics through heat flow work which had been commenced in Tasmania in collaboration with G.H. Newstead and S.W. Carey.

In February 1951, Jaeger accepted the invitation to the foundation chair of geophysics at the Australian National University, commenting that it afforded a 'magnificent opportunity'. There was criticism of his appointment at the time on account of his lack of experience in geophysics but the choice turned out to be an inspired one. His breadth of outlook and ability to penetrate quickly to the essence of fresh subjects soon showed itself as he entered his new field with enthusiasm. As preparation, one of his first steps was to attend some of Professor S.W. Carey's geology lectures at the University of Tasmania during the ensuing year, before he moved to Canberra in January 1952 to take up the chair.

The new chair was the first geophysics chair at an Australian university. Oliphant's view was that the new department should concentrate on one or two topics, with the emphasis on the physics as applied to the earth. On the other hand, Jaeger felt a broader responsibility in view of the wide range of the subject and the position in Australia at the time. However, he accepted that the scope of the department should be limited to the physics of the crust and the interior of the earth, thus excluding atmospheric physics from consideration; he also excluded oceanography on account of the expensive nature of research in that field, although this was with regret and he did dabble around the edge of the subject subsequently in connection with the International Geophysical Year. Thus, the new department was to concentrate on solid earth geophysics, still a broad field in itself, and Jaeger's view was that the approach should be closely integrated with geology, also a subject not yet pursued at ANU.

In his inaugural lecture in July 1953 Jaeger reviewed the various aspects of geophysics, presenting them in the framework of the traditional divisions of classical physics. He then stated that, in appointing a 'mathematical physicist' to the chair, the University was putting the emphasis on developing the subject directly from the fundamentals (his own predilection was to approach the subject from the applied side but Oliphant was opposed to any involvement in exploration geophysics and Tuzo Wilson had recommended a laboratory approach). Hence, he explained, since he viewed petrology and crystal physics as the essential fundamentals, his first two appointments had been in these areas (G.A. Joplin, August 1952, and M.S. Paterson, June 1953). His own immediate interest was in heat conduction, and a combined field and laboratory study of heat flow in the earth had been commenced in the first year, with A.E. Beck as the first research student in the department in July 1952. This was the state of the department in July 1953. The next appointment (E. Irving, November 1954) was in rock magnetism. Thus, apart from the petrological studies, the geophysical topics started up in the first three years were geothermy, rock deformation and palaeomagnetism. In some unpublished retrospective notes written after his retirement, Jaeger recalls that the decision as to what subjects to enter had been 'to some extent a matter of opportunism. There are certain core subjects which will expand radially into related ones provided one has a first class man at the core.... I wished to go into geothermal studies and rock deformation. I had a background in geothermal work and could organize it immediately and rock deformation seemed the fundamental link with structural geology. A third subject with enormous possibilities was palaeomagnetism with its possibilities of elucidating the problems of continental drift. I was introduced to the subject of continental drift by one of its very few champions (at the time) Professor S.W. Carey'. In these notes he also states 'I began with two strongly held but rather controversial opinions: firstly the importance of the applied side and secondly the importance of integrating geology with the subject'.

In initiating a new branch of work in the department in the earlier years, Jaeger tried as far as possible to work in it himself at first in order to gain a better feel for the subject. Geothermy was of course his own special interest, and his work in rock mechanics only developed seriously some years later (although he had already ordered some equipment in the first years), but he involved himself successively in research in petrology, rock magnetism and seismology – in the last two cases prior to making appointments in these subjects. His petrological interests initially centred around the differentiation of the Tasmanian dolerites and the rock magnetic measurements were related to these, for which he set up a simple astatic magnetometer in a small hut outside the original Geophysics building. His involvement in seismology arose out of consulting for the Sydney Metropolitan Water Sewerage and Drainage Board (MWB) and the Snowy Mountains Hydro-Electric Authority (SMA), in the course of which a plan was developed in 1955 to instal a network of seismographic stations around the MWB dam site at Warragamba and the SMA works in the Snowy Mountains, as well as a station near Canberra; the records from all stations were to be centrally processed in Canberra. H.A. Doyle was appointed in June 1956 to take charge of this seismological activity. Apart from the immediate interest in dam-filling effects, the aim was to study the modern tectonic activity of South-Eastern Australia.

This personal approach to new topics became less easy to pursue as the department broadened. Geochemical activities were introduced with the appointment of J.F. Lovering in January 1956 as a development of the petrology area, and they were intensified with the appointment of A.E. Ringwood in November 1958, introducing high pressure experimental petrology. Meanwhile, rock magnetism was strengthened with the appointment of F.D. Stacey in April 1956, and G. de Q. Robin was added to seismology in January 1957, although he only stayed for about a year. Thus there had been a substantial development of the department by the late 1950's. However it had not been achieved without some conflicts. There were some differences of opinion with Oliphant about whether to get into applied fields and there were cut-backs in projected finding from time to time. On occasion Jaeger threatened to resign over lack of support for new ventures. Such experiences, together with his regret at no longer being able to teach, led him seriously to consider returning to Tasmania to the then-vacant chair of applied mathematics in the latter part of 1958. However, he finally withheld his candidature, in part because he felt that the Department of Geophysics at ANU was flourishing and that there was a very important job to be done here'.

The early concepts of the department had not been greatly departed from up to the end of the 1950's. However, new geochemical directions were introduced in 1960 and a substantial reorientation of the Department was to occur in this decade. In discussions within the School in 1959 it was decided that the Department of Radiochemistry should be dissolved and its rock dating activity incorporated into the Department of Geophysics as part of a move into the area of geochronology and isotope geology in the latter department, and that Jaeger should visit USA and Canada for discussions and recruiting in this connection (the creation of a chair or readership had been recommended). Jaeger was conscious of the need of rock dating especially in conjunction with the palaeomagnetic work; he therefore agreed to these arrangements on condition that the subject be entered into in a whole-hearted way. The new activities came in in 1960 with the transfer of H. Berry and J.R. Richards to the Geophysics staft and an extended visit by J. Evernden from University of California, Berkeley, and they were strengthened with the appointments of W. Compston in January 1961, and I. McDougall in August 1961. The geochemical activities were further strengthened with the appointment of S.R. Taylor in January 1961, D.H. Green in April 1962 and K.S. Heier in August 1962. Geochemistry was now, if anything, stronger than geophysics in the balance of the department and this was recognized in 1964 by renaming it the Department of Geophysics and Geochemistry.

With the appointment of J.R. Cleary in 1965 in seismology and M.W. McElhinny in 1967 to replace Irving, the main staff structure of the department which persisted for the remainder of the decade and into the 1970's was established. The high calibre of the work of the department over these years reflects great credit on the remarkable perspicacity of Jaeger in selecting people.

Another important aspect of Jaeger's development of his department was the establishing of links and joint arrangements with other organizations, notably in seismology, geochronology, palaeomagnetism and rock mechanics. An early example was the setting up of a line of seismic recording sites in 1956 to take advantage of the nuclear bomb tests at Maralinga for exploring crustal and upper mantle structure, an operation that put heavy demands on the technical and manpower resources of the fledgling department at the time. A similar arrangement was made to take advantage of a large quarry blast at the Eucumbene dam site in the Snowy Mountains in 1957. Jaeger's role in the setting up of a network of seismic stations in the Snowy Mountains to Sydney region and its monitoring from Canberra has already been mentioned. He was later to arrange for the department to take on the responsibility for operating the British seismic array for nuclear test detection, near Tennant Creek, Northern Territory, in return for access to the records (this operation was at first done jointly with the department of Engineering Physics and later taken over entirely by Geophysics).

Since the time of his appointment Jaeger had maintained contacts with the Bureau of Mineral Resources but, except for an arrangement for three of their staff to be attached to the department for a period as research students in the mid-1950's, the first major collaboration arose in the fields of geochronology and palaeomagnetism from 1961. An agreement was made whereby the Bureau contributed substantially to the cost of equipment and maintained several workers in the department so as to provide geochronological and palaeomagnetic services for the Bureau.

In rock mechanics, the outside links came mainly through his consulting, an activity that very well suited his liking for being involved in applied problerns. Thus he had an involvement over many years with the Snowy Mountains Hydro-Electric Authority, first with heat flow measurements and triaxial testing of rocks and then, more significantly, with in situ measurement of rock stress. In the latter connection, new field procedures were pioneered in conjunction with the Authority and also with the Chamber of Mines in Johannesburg during visits on study leave. This work was integrated with the rock mechanics research that he was conducting in the department. A similar close relationship between the consulting activity and the research of him and his students arose from work with other organizations; apart from the Snowy Mountains and South African connections he at various times was consultant to NORAD, Colorado Springs, USA, Broken Hill South Limited at Kanmantoo, South Australia, CRA at Bougainville, Mt. Isa Mines at Mt. Isa, and Bechtel Corporation at the Manapouri hydroelectric project in New Zealand.

An example of Jaeger's drive in promoting significant geophysical measurements in the face of considerable financial and administrative hurdles can be seen in his organizing of the drilling of boreholes to aid direct physical and geological measurements in parts of the crust otherwise inaccessible. Although boreholes are often drilled for engineering and mineral prospecting purposes and Jaeger sought access to these wherever possible and appropriate, other holes are required in regions where no direct economic incentive exists for commercial drilling and he did not shrink from deploying the considerable funds required in these cases. In this way, holes came to be drilled for research purposes in Tasmania, near the coast in New South Wales and, notably, under the auspices of the Australian Upper Mantle Project, in Western Australia (a traverse of four holes).

When Oliphant relinquished the Directorship of the Research School of Physical Sciences at the end of 1963, Jaeger was appointed as Acting Head for two years, with the title of Dean, at the same time continuing as head of the Department of Geophysics. One of his main acts as Dean of the School was to reorganize the former Department of Particle Physics as the Department of Engineering Physics and bring in G.H. Newstead as its head. At the same time the Diffusion Research Unit was created, completing the redirection of the resources of the former Department of Radiochemistry. Otherwise, his period as Dean is recalled as one of effective management without dramatic highlights, a 'vintage period' according to the laboratory manager (A.A. Robertson) at the time.

After completing the term as Dean, Jaeger remained as head of the department until September 1971. There were no major developments in the structure of the department during this time, but it was a period that saw a heavy involvement in research on lunar samples from the American missions, and also the completion in 1969 of the building, later named the 'Jaeger Building', which was to house the whole department together for the first time since 1956 (an earlier stage had been completed in 1965, prior to which the department had been spread through as many as five buildings). The last two years of this period also saw intense negotiations that were to lead finally to the creation of the Research School of Earth Sciences, noted below. It was also a period when Jaeger began to be troubled by illnesses, which were affecting his mobility by 1971. However, 1970 finally saw the recognition which probably gave him the greatest satisfaction as the pinnacle of his career, his election to Fellowship of the Royal Society. After retiring as head of department, Jaeger stayed on as professor of geophysics until his retirement from the University in December 1972. He was then given the title of Emeritus Professor.

During Jaeger's years at ANU he served on many national committees concerned with earth science and allied fields, notably on the National Committee for Geodesy and Geophysics and the National Committee for the International Geophysical Year (1957/1958). He was particularly active in the Academy committees on research in oceanography, emphasizing the glaring inadequacy of the Australian effort and attempting to promote a much greater activity in this field, although the support for oceanographic research continued to be meagre during his years in Canberra. He also served on a committee that was set up in 1966 to review Antarctic research under the Department of External Affairs. However, the most important legacy of his efforts to promote research in the earth sciences in Australia was the Research School of Earth Sciences at the Australian National University.

The original intention in starting a department of geophysics within the Research School of Physical Sciences had been that it would be a small group with a staff of three or four, housed within the main buildings of the School. However, difficulties of accommodation had led almost immediately to a small separate building being constructed for the Department, giving it the appearance of a degree of independence. That this was to become more than an appearance was soon foreshadowed in Jaeger's plans for development. Already in January 1955 he was writing to the Vice-Chancellor that 'it will be apparent that a much larger staff than is usual in a department is necessary to cope with Geophysics and my hope is that the present department might be regarded as an embryo School of Earth Sciences'. This seems to have been the first proposal for a School although in his first year, in June 1952, he had already written to the Vice-Chancellor about possible collaboration with CSIRO or the Bureau of Mineral Resources, in these terms: 'At the present time the Department of Geophysics is envisaged as a small unit which will specialize in one or two branches of the subject.... If it is really to cover Geophysics, it will need to have a larger staff and the problem in my mind is how to get it'. He raised the issue of a School again in July 1956 in connection with capital estimates, evidently with some effect since the site consultant Professor D.W. Winston wrote to the Registrar in November of that year that, inter alia the present School site 'would be suitable for a new School of Geophysics' and for some years the building development on the site was labelled 'Earth Sciences', although this was later changed to 'Geophysics'. The issue was pressed further by Jaeger in 1961 and 1962, with a detailed 'Case for a Centre of the Earth Sciences at the ANU', when it was taken as far as the board of the Institute. Final success came after the re-opening of the issue in 1969. Jaeger again pressed the case hard but, with his retirement imminent, he now also took the view that the exact arrangements in any outcome were more appropriately negotiated by the members of the Department, who would be most affected by them. The final campaign was therefore mainly led by Professor Ringwood with the backing of the, by then, large and flourishing Department of Geophysics and Geochemistry. The inauguration of the Research School of Earth Sciences in July 1973, just after Jaeger's retirement, thus represented the culmination of a persistent effort carried on by him for two decades to build up a major centre of the earth sciences.

Personal research at ANU

Although he moved into new fields at ANU, Jaeger retained his involvement in the theory of heat conduction and it continued to occupy him a good deal until well into the 1960's, being represented in at least one half of the papers which he published in the first ten years in Canberra. Also in this period he did the extensive revision of Conduction of Heat in Solids published as the Second Edition in 1959. However, heat conduction became increasingly an adjunct to his geophysical interests and the Canberra papers tend to be more concerned with applications than with new solutions. There were two main themes, firstly, problems in transient heating and, secondly, the study of problems with cylindrical geometry, especially involving boundary conditions at an internal cylindrical surface. In addition there were a number of papers on heat conduction or diffusion where complicated shapes were concerned, mainly in connection with the cooling of intrusive igneous bodies, mentioned later, and there were several excursions into physiology.

The treatments of transient heating were particularly concerned with applications to such problems as 'the temperatures developed in rotating anode X-ray generators and the frictional heating at sliding contacts'. They included cases of pulsed or periodic heating and so were also applied to the diurnal heating of the earth's surface, and to the lunar problem mentioned earlier. The papers on problems with cylindrical geometry dealt with three types of applications, all deriving from the basic theory, set out in the 1956 papers. One of the applications was to the transient heating of electrical cables. Then there were a number of papers concerned with geothermal problems, such as the use of cylindrical probes in boreholes for the determination in situ of the thermal conductivity of rocks, and the analogous hydrological problem of draw-down of wells. And finally there was the application to mine ventilations, a topic that Jaeger became involved in with both the Broken Hill and the South African mines.

Since the differential equation governing diffusion is identical with that for heat conduction, the mathematics developed for the latter applies equally to the former. Jaeger therefore on occasion became involved in applications to diffusion problems. In this connection, he was drawn into the theory of diffusion in a physiological situation by Professor J.C. (later Sir John) Eccles with whom he wrote a paper on the diffusion of transmitter substance in the junction regions of nerve cells. This work led on to two further papers on diffusion in physiological situations, including more complicated geometries. Heat conduction itself in biological tissue was dealt with in an earlier paper in which the effect of blood flow was taken into account; this paper covered similar ground to his unpublished war-time work on the heating of the eye by infrared radiation, already mentioned. Finally, there was a further paper of some relevance to physiological research which dealt with temperature distribution where a highly conducting wire is in contact with a poorly conducting mass, of particular application where thermocouples are used to determine temperatures in biological tissue.

Jaeger's entry into actual geophysical research at ANU was with the measurement of the geothermal flux, that is, the rate of heat flow from the Earth's interior to its surface. This subject continued to involve him throughout his period in Canberra and into his retirement, and his influence extended further through a series of students who worked with him on it: A.E. Beck, L.E. Howard, J.H. Sass and R.D. Hyndman. It represents his most important direct contribution to geophysical research, covering the methodology of the subject, the determination of the regional heat flow pattern itself, and its interpretation.

The determination of the geothermal flux involves two measurements, firstly of the vertical temperature gradient at a given locality, usually made in a bore hole or a tunnel, and secondly of the thermal conductivity of the rock in which the temperature gradient exists, usually made on drill-core taken from the borehole. In the first connection, Jaeger gave careful attention to the question of how long one should wait after drilling for the perturbing effect of the drilling itself to decay before making the temperature measurements, particularly taking into account the circulation of drilling fluid in the hole. Corrections for topography and climatic history were also worked out and the question of how deep a hole should be was considered. In connection with the determination of thermal conductivity, Jaeger made a particular study of transient heat-source methods, suggested by his theoretical work on heat conduction. With various collaborators, probably beginning with a visitor in the department, J.H. Blackwell, he studied both laboratory and in situ techniques involving transient heat sources. However despite the elegant theoretical basis for these methods, practical difficulties (primarily the problems of achieving satisfactory thermal contact and tolerable levels of undetected heat loss) proved to be such that, rather than replacing the conventional steady state divided bar method, they are only used in special cases as an adjunct. But the study did have indirect benefits in improving the knowledge of water movement in boreholes, a topic which is of some engineering interest.

The early discovery of relatively high heat flow in Tasmania and in the Snowy Mountains of New South Wales and then of low-to-normal heat flow in the Precambrian shield of Western Australia stimulated efforts to gain as wide a coverage of measurements as possible throughout the continent, an effort that continued in later years especially through a joint programme with the US Geological Survey under Jaeger's former student Sass in the late 1960's and early 1970's. Published results that included Jaeger's authorship and a number that did not are summarized together with those of the later joint ANU-USGS work in the 1975 US Geol. Survey Open-File Report No. 75-567 by R.J. Munroe, J.H. Sass, G.T. Milburn, J.C. Jaeger and H.Y. Tammemagi, entitled 'Basic data for some recent Australian heat flow measurements', and their interpretation is discussed in the 1976 US Geol. Survey Open-File Report No. 76-250 by J.H. Sass, J.C. Jaeger and R.J. Munroe, 'Heat flow and near-surface radioactivity in the Australian continental crust'. Further summaries appear in F.E.M. Lilley, M.N. Sloane and J.H. Sass, 'A compilation of Australian heat flow measurements' ( J. Geol. Soc. Aust. 1977, Vol. 24, 439-445) and in J.H. Sass and A.H. Lachenbruch, 'Thermal regime of the Australian continental crust' (pp. 301-351 in The Earth: Its Origin, Structure and Evolution, Ed. M.W. McElhinny, Academic Press, London, 1979). The outcome has been to delineate three broadly distinct regions in respect of heat flow; one is a region of high heat flow trending roughly from the Northern Territory to South-Eastern Australia, and it separates the other two, the Western and North-Eastern regions, which are of relatively low heat flow.

As regional variations in heat flow began to emerge, Jaeger became aware that their interpretation would involve taking into account the near-surface radioactive heat production. He therefore sought the cooperation of various people (especially K.S. Heier and I.B. Lambert) to measure the radioactivity of representative granitic and metamorphic rocks using gamma-ray spectroscopy. Correlation of these measurements with heat flow measurements supported the idea that the heat of radiogenic origin was mainly generated in a shallow layer of a few kilometres in the crust and that, in a given region, the variation in heat flux can be related to the variation in concentration of radioactivity in this layer. A summary of this and later work on the relation of Australian heat flow figures to radiometric heat production is given in the context of work elsewhere by Sass and Lachenbruch (1979, quoted above).

Jaeger's interests in heat flow also led him into various studies concerned with igneous intrusions and their effects. The earlier work was on differentiation in dolerite sills, partly in conjunction with G.A. Joplin and, later, R. Green. The heterogeneity of the sills was revealed by various physical observations (magnetization, susceptibility, density), done in part to demonstrate the possible contribution from simple physical measurements. Some ideas about the short life of settling crystals and about the possible role of the stoping of partly-solidified crystalline mushes gave rise to some healthy controversy at the time and in a later review Jaeger admitted that neither had 'found favour'. A farther-reaching contribution, founded in Jaeger's experience in the theory of heat conduction, comes from a series of papers on the cooling history of intrusive bodies and the thermal effects in their neighbourhood. These papers refined and extended the previous theories in this area and paid particular attention to the implications for such matters as melting, metamorphism and argon loss near the contacts and jointing and differentiation within the intrusive body. Finally, Jaeger's interests in magmatic bodies were not confined to theory and laboratory observations on intrusives. He took the opportunity whenever possible to see field occurrences of both intrusives and extrusives. On a number of occasions when on study leave he visited volcanic regions and intrusive complexes (in particular, Mauritius-Reunion, Hawaii and the Bushveld) in connection with columnar jointing, lava temperatures and solidification patterns, and differentiation. Thus in one study leave report following a trip in 1966 he comments that a new lava lake in Hawaii was solidifying as he had predicted.

Coming now to Jaeger's other geophysical research, his brief excursion into rock magnetism has already been alluded to in connection with the petrological differentiation of dolerite. While he was primarily concerned with elucidating the geological history of the bodies concerned, he was also conscious of geophysical aspects, for example, in discussing observations on reversed magnetization and possible secular variation. He did not himself follow the subject into its palaeomagnetic applications except for taking part in some of the early discussions in the relative movement of continents in association with Irving. However, his readiness to espouse the notion of continental drift at that time, in which he was at least partly influenced by Carey, put him in the forefront of geophysical thinking in this area. Jaeger's activity in seismology was mainly entrepreneurial but of considerable significance in connection with the early measurements on crustal thickness using nuclear and other large explosions and with the establishment of the seismic station networks, already mentioned. Several publications deal with these activities and the significance of results arising from them, both in relation to the seismicity of Australia (he had a special interest in its connection with geological structure) and to engineering developments. Finally, the installation of long ocean wave recorders for the International Geophysical Year permitted some observations on the nature of these waves, as well as of the arrival of the tsunami from the 1960 Chilean earthquake (the only tsunami detected in four years of recording). Jaeger concluded that it was possible to detect long ocean waves in relatively sheltered harbour sites even though modification occurs.

The fifteen years prior to retirement saw yet another phase in Jaeger's scientific orientation, when he concentrated most strongly on rock mechanics. There had been an incidental interest in rock fracture at one time in Tasmania, and an intention to enter the field more seriously was shown by his purchase of a 500 ton compression testing machine soon after taking up his appointment in Canberra. By this time he was already involved in rock mechanics consulting with the Snowy Mountains Hydro-Electric Authority and he later attributed his fascination with rock mechanics as coming from T.A. Lang, then Assistant Commissioner of the Authority and a great friend. However, he did not become extensively involved in experimental rock mechanics until about 1958. From this time onwards he spent considerable time in conducting his own experiments in this field, helped by Mr W. McIntyre. He later had several research students working in the same area (E. Hoskins, K.J. Rosengren and B.A. Chappell) and collaborated from time to time with South African workers (N.G.W. Cook and N.C. Gay), as well as engaging in engineering consulting in rock mechanics. His work was almost entirely concerned with the brittle field of rock behaviour, with emphasis generally on the macroscopic aspects rather than the study of microscopic mechanisms, partly because the latter were not readily accessible with the techniques available at the time and partly because of his interest in engineering application. In connection with the practical application, he obviously enjoyed relating that 'the engineering approach goes back to the architects of the Pantheon in Paris who designed the stone columns on the basis of tests in a testing machine which they built for the purpose'. On the development of his interests he writes: 'My own interest in the subject came from contact with the SMA [Snowy Mountains Authority] who were concerned with problems of the design and construction of underground power stations. The problem arose of what were the stresses around such openings; they were usually calculated on the assumption of ideal elasticity which was obviously far from correct. I can remember the pleasure with which I received Talobre's La mécanique des roches [Dunod, Paris, 444pp.: 1957] which first set out (for me) the principles that the fundamental things to study were (i) the properties of joints and (ii) that the fundamental building blocks were the irregular pieces of rock between the joints which would be very irregularly loaded. This suggested the importance of studying the behaviour of rocks under complicated systems of loading rather than the conventional tests. Much of my work has been directed toward the study of the effects of unusual types of loading'. Typically, his approach involved simple but perceptively designed experiments and was marked by his extraordinary ability to penetrate to the fundamental order in the rather scattered and complicated experimental results. Broadly one can distinguish three areas which his work spans: the exploration of various types of laboratory tests, especially in respect to the nature of the failures produced and the determination of the tensile strength of rock; the study of friction at rock interfaces and the extension of this to the behaviour of jointed or broken rock; and some aspects of applied rock mechanics such as slope stability and in situ stress measurement.

In the first area, an early paper on axial splitting versus shear failure in triaxial tests at low confining pressure and an important, seminal paper on shear failure in anisotropic rock preceded a series of papers on a wide variety of tests complementary to the conventional triaxial test, involving punching, pinching-off (Bridgman), and diametral loading of solid and hollow specimens, and including combination with superimposed hydrostatic or uniaxial loading. The results of such tests were compared with those of conventional tests, usually in terms of the Coulomb criterion of failure and a special study was made of the indirect ways of obtaining the tensile strength of rock, showing, for example, that the Brazilian test (diametral loading of a solid cylinder) gave reliable results whereas diametral loading of hollow cylinders did not. The analysis of the pinching-off test was extended to explain the disking of drill core during drilling of deep holes and some of the earliest observations on the role of the intermediate principal stress were made. This phase of the work was summarized in two admirable review papers.

In the work on friction, there was again careful attention to the methods of test and a number of important observations were made, in conjunction with several collaborators, on the role of surface finish, on gouge formation, and on the stick-slip phenomenon. This work probably had more immediate scientific impact than any of the other rock mechanics work and it established Jaeger as one of the principal authorities on friction in rock at the time. This position was reinforced by his Rankine lecture to the British Geotechnical Society in which a comprehensive survey of knowledge on friction in rock was given. The friction work was related to the study of joined rock, both directly through the study of friction in natural joints and indirectly, in its role in the movement on joints in the deformation of joined rock. Studies on the latter topic involved the modelling of interlocking joints by the use of thermally disaggregated marble, the direct triaxial testing of large cylinders of closely-jointed rock from Bougainville and Mt. Isa, and the study of granular material under confinement. Jaeger also supervised a student, B. Chappell, who worked on photoelastic models of jointed rock but was not involved in any publications with him. At the same time Jaeger was interested in the application of studies on jointed rock to practical design problems, also dealt with in his Rankine lecture.

In no area did Jaeger's interest in engineering applications find fuller expression than in his consulting work in rock mechanics and its integration with his experimental work. Early contact with design problems in the Snowy Mountains project and in the South African mines fired his interest and some of the first triaxial tests done in the Canberra laboratory were on granitic gneiss samples from the first underground power station excavation in the Snowy Mountains (the present writer was drawn into doing these in about 1954). The Snowy Mountains Hydroelectric Authority soon developed their own testing facilities but Jaeger retained a strong connection with their rock mechanics and engineering geology work, especially through T.A. Lang and D. Moye, and he participated particularly in the development of techniques of in situ stress measurement, both there, where the SMA had developed their own flat jack method, and in South Africa. Only one paper was published on the subjects but he made considerably more contribution in consultation and in calibrating particular techniques in his own laboratory so as to check on their reliability, a matter of some concern, especially in jointed rock.

This and other activities in rock mechanics consulting have already been mentioned (Mt. Isa, Bougainville, Manapouri, Kanmantoo). Finally, again arising out of practical requirements, it may be mentioned that, with Rosengren, he also designed a simple device for borehole surveying.

Jaeger's most far-reaching influence in rock mechanics has again been through books. In 1956 he published Elasticity, Fracture and Flow in the Methuen Monograph Series. This gave a very concise account of the elements of the theories of elastic and non-elastic behaviour, with which was integrated just sufficient of the fundamental physics of mechanical behaviour to give the reader a reasonably well-balanced view. It was a very successful book, well-suited for students with minimal mathematical background and for quick reference, and particularly oriented towards geology and engineering. He significantly enlarged and updated it in two subsequent editions in 1962 and 1969. Rather similar material appears in a later, larger book entitled Fundamentals of Rock Mechanics, also published by Methuen in 1969. This book was written in collaboration with N.G.W. Cook and it contains, in addition to the basic material just mentioned, a more detailed development of the applications of the theory of elasticity, a much fuller account of mechanical testing of rocks in the laboratory and of the nature of the brittle behaviour of rock, and several chapters on in situ stress measurement and on geological applications. It has become a standard textbook in the field and has been revised, largely by Cook, in a second edition in 1976, and again by Cook for a third edition in 1979. It was recognized by the award to Jaeger and Cook of the first Rock Mechanics Award of the American Institute of Mining, Metallurgical and Petroleum Engineers in 1969. In his last two years before retirement Jaeger wrote a number of sections for a large collaborative work, with N.G.W. Cook and T.A. Lang, intended to be an encyclopaedia or handbook of applied rock mechanics, but this work is still being prepared for publication. He also left some sketched-out chapters for a book on structural geology, a project that seems to have been in his mind for many years but which never came to fruition.

Retirement

At the end of 1972, when Jaeger retired from ANU at the age of 65, he and Patty left Canberra and returned to Tasmania. They sold 'The Oaks', together with the collection of steam engines and agricultural machinery, and bought another early stone house at Saltwater River, on the Tasman Peninsula about 100km from Hobart. This house had been built as part of the convict settlement there. It had at one time been in Patty's family, and was not far from 'Lottah' where she had grown up. It was in a beautiful and tranquil setting overlooking Norfolk Bay but was very remote from most services. Jaeger's colleagues deplored the retreat into isolation but Patty was very keen to return to Tasmania and Jaeger shared its lure although he later admitted that he regretted being so cut off from the world of scientific affairs.

Back in Tasmania, Jaeger carried on some writing, mainly clearing up some collaborative papers, and he kept up some correspondence on heat flow, rock mechanics and his books. He had intended to prepare a further edition of Heat Conduction in Solids but made little progress on it. In March 1975, the University of Tasmania honoured him for his distinguished career and his long connection with that university by conferring on him the honorary degree of doctor of science; the citation welcomed him 'back to the Tasmanian scientific and education community, in which he played so prominent a part during his previous sojourn in this state'. Jaeger also made a few short trips back to ANU during the first year or so of retirement. However, his health soon proved to be a serious impediment to these activities.

Jaeger's health had troubled him for a number of years even before retirement. He had had an operation in late 1965 from which he was slow to recover and from about 1971 he used a stick for walking. There were some three further operations in 1971-1973 for various reasons, during one of which he suffered a heart attack. Then from about 1973 his eyesight began to fail seriously, which limited his work and made correspondence more difficult, although he continued to be able to read clear print even in later years. The remoteness of Saltwater River made access to good medical services difficult and added to make his condition more miserable in his last years. It was perhaps in this context that he is reported to have said, replying to an enquiry as to why he had called the house there 'Thule', that it meant 'the ultimate bloody end'. In December 1974 he wrote 'I couldn't have chosen a worse place than this for being ill in'. He was persuaded to make a further visit to Canberra in November 1976 in the company of Professor Gordon Newstead but declined to come again in the following year, saying that his sight had deteriorated so that he could no longer do 'any useful work'.

Patty had remained active until July 1978, when now aged 77, she had to be taken to hospital where she died within about two weeks on 31 July. This was a great blow to John who was devastated by her loss, having seemingly decided that he was to die before her. He lived on by himself at Saltwater River in poor health and miserable circumstances, although helped by visits from Patty's nieces, especially Mrs Christine Dobner. However, possibly in desperation because of lack of medical attention, he agreed to move to Canberra in late 1978. Here he alternated between Canberra Hospital and University House, with much support from Mr and Mrs J.H. (Gus) Angus, until he died on 15 May, 1979.

Personal qualities

Having completed the narrative of his life and work, it is now time to recall in more detail the sort of man that Jaeger was. Physically, he was tall and slim in his youth, but his ample frame filled out very much in his middle years and, although in his last years he shed much weight, he is mainly remembered as a very large man, slightly stooped, with large head and receding hair, and aptly described on occasion as a 'large, teddy-bear sort of man'. In casual encounter and in the greater part of his relations with his associates he showed a genial personality, warm although never effusive. However, when he was busy or preoccupied, he tended to present a rather gruff front, and at times he could be downright grumpy, but his moods represented a sort of withdrawal and were never of a malicious kind; once this external barrier was overcome, he was generally easily approachable and accommodating. Although he liked there to be clear cut rules to guide administrative decisions, he was intolerant of unnecessary bureaucracy and organization. For example, when a student of mine, seemingly to ensure being in good grace, asked him what hours he should keep in the laboratory, Jaeger replied that it did not matter and that the less he saw of him the better. Jaeger also had an aversion to the telephone, although he made good use of it when it suited him; the telephone at 'The Oaks' used to be kept under a meat-dish cover.

Jaeger is generally remembered by early associates as being very shy and this was probably an underlying quality affecting his personality throughout his life, although he could appear quite outgoing at times. There was, in fact, something of a paradoxical contrast between his widely-felt presence on the scientific scene and his retiring nature in the presence of people. He tended to seem ill-at-ease with his peers and to have easier relationships with junior colleagues or subordinates. There was an occasional appearance of favouritism in treatment of staff, which in turn could involve a dramatic reversal of fortunes when circumstances changed, but on the whole he was fair-minded. Women played a particularly significant role in his life. Looking back on what one knows of his private life, it would appear that in his more productive periods there was always a woman who played an important part or on whom he depended considerably, notably his mother in early years and Patty in latter years, and it was also characteristic of him that he sought out and enjoyed the company of women.

Of Jaeger's interests outside science, two immediately come to mind. The first was his passion for cats, which seems to have been with him all his life. Thus there is an early photograph of him, still in short pants, holding a cat. He is remembered as having arrangements for cats in his laboratory at University of Tasmania, and in ANU days and in retirement there were always large numbers of cats in the Jaeger household. He also had a considerable collection of books about cats, especially literary works such as T.S. Eliot's poems. The second passion was for old machinery, including steam engines. This was part of a general antiquarian interest, probably also reflected in his earlier interest in archaeology. In his Cambridge and Tasmanian days he enjoyed walking as a recreation and he also enjoyed cooking. His interests in reading tended to be in the nineteenth century. He had a particular liking for Dickens and also enjoyed such writers as Byron and Walpole. He had been fairly strictly brought up in the religious observances of his day but in later years he had little interest in religion and was cynical about conventional religious ideas. His political views were largely on the conservative side.

Conclusion

Jaeger clearly emerges as a major figure in Australian science, remarkable for the breadth and multifacetedness of his career in teaching, in administration and in research. He made major contributions in at least three fields – applied mathematics, earth science and engineering – not to mention lesser contributions in a number of other fields. First he achieved fame as an applied mathematician, especially through his books and his teaching; Conduction of Heat in Solids alone would have ensured continuing international recognition. Then he became one of the major moving forces in solid-earth geophysics and geochemistry in Australia, founding a school of high international standing and making important contributions in geothermal studies and rock mechanics. In addition, much of his research in rock mechanics and his advisory activities in this and other fields must be regarded as substantial contributions to engineering, representing a link to the practical world.

Jaeger's scientific work was especially notable for its practical or applied aspect. His brilliance lay not so much in the origination of new ideas or insights but in the perceptive development and application of existing concepts, both in theoretical and practical directions, and mainly in the areas of classical physics. In this, he brought to bear an extraordinary intuition for the essence of a problem. A similar intuition served him in his role as administrator, including in the selection of people.

As a person, Jaeger is remembered with affection and respect by his colleagues and acquaintances, and many have benefited by his kindly interest. Yet in spite of his wide influence and connections he was rather shy and retiring and relatively few people were on intimate terms with him. He was at the same time conservative and unconventional in his views on life, but with deep cultural roots. In all, he was a remarkable and original man.

Acknowledgements

Many people have helped me with material for this memoir, too numerous to mention them all. However, I should like to thank especially Miss Margaret Sladden, Mrs Christine Dobner, Mr & Mrs Peter Shoobridge, Mrs Cynthia Alexander, Mrs Joan Parks and Mrs Joan Thorp for personal details, and E.J.G. Pitman, S.W. Carey, G.H. Newstead, E.G. Bowen, Sir Mark Oliphant, Germaine Joplin, E. Irving, I. McDougall, J.H. Sass, A.L. Hales, R.A. Hohnen and N.G.W. Cook for extensive information on other aspects of John Jaeger's career. Access to records at the University of Tasrnania and the Australian National University has also been very helpful.