Bertha Swirles was born in Northampton, the daughter of William Alexander Swirles and Harriett Blaxley. She was educated at Northampton School for Girls and came up to Girton College in 1921 to read Mathematics. She was awarded her PhD in 1929. A fellow research student was Douglas Hartree, who became a lifelong friend.
She lectured successively in Manchester, Bristol, Imperial College London and Manchester before returning to Cambridge and Girton in 1938 to take up a Fellowship and Lectureship in Mathematics. She remained at Girton for the rest of her career: amongst a number of College offices, she served as Director of Studies in Mathematics and Mechanical Sciences for many years; she was also Director of Studies in Music for a number of years; she was Treasurer of the Girton Working Women's Summer School; and she was Vice-Mistress from 1966 to 1969. She was appointed a Life Fellow of Girton in 1969.
In 1940, Bertha Swirles married Harold Jeffreys (later appointed Plumian Professor of Astronomy at Cambridge and knighted in 1953). Her collaboration with him led to their co-authorship of Methods of Mathematical Physics, first published in 1946 and revised and reprinted for well over fifty years.
Bertha Jeffreys died on 18 December 1999. A fuller biography, compiled for St John's College Cambridge by Timothy E Powell and Peter Harper of the National Cataloguing Unit for the Archives of Contemporary Scientists, can be found on the Janus website under St John's College Library, JeffreysB.
The papers include school records; biographical materials; photographs; notes on travel and excursions; some miscellaneous correspondence; and some papers of Bertha Blaxley (one of Bertha Jeffreys' maternal aunts).
Before her death in 1999, BJ arranged that the combined papers of Sir Harold and herself should be catalogued by NCUACS and then go to the archives of St John's College, Cambridge. She extracted some material to come to Girton, which would reside as a separate entity in GC archives (not catalogued by Bath). After the main material was deposited, St John's offered Girton the option of taking some of BJ's papers for deposit in Girton's archive. The Archivist and the Librarian examined the catalogue listings. Two issues emerged: the first was the coherence and integrity of the combined collection; the second was their personal knowledge of BJ's wishes, namely that her papers, both personal and professional, should be kept with Sir Harold's. They decided therefore to leave the papers located at St John's and not to disturb the order established by the cataloguing process. References between St John's and Girton's archival collections would be established, not least via Janus. In this way the collection would retain its coherence, but no item would be lost to any researcher regardless of location.