Born in Northampton in 1903, she was involved in the world of education from her earliest days. Her widowed mother was a primary-school teacher and various aunts were also teachers. She attended Northampton School for Girls and then went up to Girton, in 1921, to read Mathematics, graduating with first class Honours.
She became a research student of R.H. Fowler, one of a distinguished company of his students which included several Nobel prizewinners such as P.A.M. Dirac and Subrahmanyan Chandrasekhar. She spent the winter semester of 1927-28 in Gottingen, where she worked under Max Born and Werner Heisenberg and interacted with many of the other leading continental workers in the relatively new field of quantum mechanics; it was an exciting time.
By the time she was awarded her PhD in 1929, she was already an Assistant Lecturer in Manchester. This was followed by similar appointments in Bristol and at Imperial College, London, and then in 1933 she returned to Manchester as a Lecturer in Applied Mathematics. Douglas Hartree at Manchester was extremely sorry to lose such a valued colleague when she returned to Cambridge in 1938, to an Official Fellowship and Lectureship in Mathematics at Girton.
In Cambridge, Bertha Swirles continued to publish important papers on quantum theory, but her most widely known publication is the enormously influential text Methods of Mathematical Physics, written with Harold Jeffreys, whom she had married in 1940. It was first published in 1946 and, after many editions and revisions, it was reprinted a few weeks ago, with a delightful picture of Bertha and Harold on the back cover. It has educated many generations of students and is still a recommended text for several undergraduate mathematics courses in Cambridge today. The book covers a huge amount of material and is written with great clarity (and even humour, in the choice of quotations at the start of each chapter). It was the fruit of many years of work.
Subsequently Bertha Jeffreys's research interests broadened to include seismology in collaboration with her husband, who was by then Plumian Professor of Astronomy at Cambridge. He was knighted in 1953. Theirs was a long and happy marriage, the main bone of contention seeming to be whether he should still be cycling in his shorts in his eighties. He died in 1989 when he was almost 98.
Bertha felt an immense loyalty to Girton and played a very active role there, holding a large variety of college offices at various times, including that of Vice-Mistress from 1966 to 1969. She will perhaps be remembered most in her capacity of Director of Studies in Mathematics, a post she held from 1949 to 1969. This involved selecting, advising and teaching generations of women mathematicians, who have themselves gone on to propagate her influence to ever wider circles. Her supervisions were informative, stimulating and enjoyable (even when the students was referred firmly to Fowler's Use of English) and she had an intuitive sense of the particular difficulties each individual faced.
She took a personal and warm interest in all her students and there was often "open house" for them on Sunday evenings at the Jeffreys residence halfway between Girton and the centre of Cambridge. Her interest did not cease when students left Cambridge; she and Harold had no children, but there was an enormous extended family based on her former pupils. She had an amazing memory for the details of their lives. When their children and grandchildren arrived in Cambridge as students themselves, they would be invited to tea. This used to involve sampling Bertha's homemade flapjack whilst Sir Harold sat on the floor doing the Times crossword. Many a younger child received an imaginatively chosen birthday gift from Auntie Bertha.
Not suffering fools gladly made Bertha Jeffreys seem a little formidable to some. She set the highest standards for herself and expected others to do the same. Her advice was never stereotyped; she approached each problem with an open mind, coupled with sensitivity and an enormous amount of common sense. Although she was sometimes a little irritated by activities for women mathematicians, feeling that progress would come from women doing good mathematics rather than spending time pondering their difficulties, she was always extremely supportive of individuals.
Music was an important part of her life. She was an accomplished pianist and cellist, and still played piano duets with a friend in her nineties, when she also still regularly attended concerts in college and at Kettle's Yard.
Bertha Jeffreys played a leading role in women's education this century, and she inspired students of mathematics world-wide. It is a pity that only after her husband's death did she receive honorary doctorates, from the University of Saskatchewan in 1995 and the Open University in 1996. This recognition of her would have given him great pleasure.
Her colleagues, pupils and friends will miss her wisdom and her generosity, her "unstuffy" approach to life and her sense of fun. Her 90th birthday lunch was attended by about 140 of her former pupils and colleagues from several continents, a fitting tribute to a very special teacher and friend.
R. M. Williams
Bertha Swirles, mathematician: born Northampton 22 May 1903; Fellow, Girton College, Cambridge 1938-69 (Life Fellow 1969), Director of Studies in Mathematics 1949-69, Vice-Mistress 1966-69; married 1940 Harold Jeffreys (Kt 1953, died 1989); died Cambridge 18 December 1999.