THE ELDEST of eight children born to J. M. Balfour and Blanche, daughter of the second Lord Salisbury. Among her brothers were
Arthur, who became Prime Minister, Francis, an outstanding biologist who died young in a mountaineering accident, and Gerald, a philosopher. Deeply interested in pure mathematics, which she thought 'specially suited to a disembodied existence', she collaborated with her brother-in-law,
Lord Rayleigh in experimental work on electrical standards of measurement, and
in three papers published in the Philosophical Transactions of the Royal
Society. In 1874 she sat with various physical mediums but was not impressed. She married
Henry Sidgwick in 1876. Closely connected with Newnham College all her life, she served as its Treasurer for many years, and as its Principal from 1892 to 1910.
She joined the SPR in 1884, edited its Journal and Proceedings from 1888 to 1897, became a Council member in 1901, and was Honorary Secretary from 1907 to 1932. An admirable administrator, she also contributed many reports to the Society, reports which exemplified her clarity of thought, her energy and her enormous industry. Among them were studies of
Mrs Piper's trance phenomena (she thought her
'control' was 'some element of her own consciousness') and of Mrs
Leonard's Book Tests, in which she suggested that clairvoyance might be involved; she also wrote on
Gilbert Murray's telepathy experiments. She helped to compile
Phantasms of the Living and the first Census of Hallucinations, and wrote many papers for
Proceedings from one on 'Phantasms of the Dead' in 1885 to one on 'The History of the SPR' in 1932.
Mrs Salter, who had known her for many years both at home and at Cambridge said in an article setting out her brilliant, solid work, 'I never remember hearing her make anything that could be called a joke', but paid tribute to her 'twin qualities of intellect and character'.
Source (with minor modifications):
The Society for Psychical Research, 1882-1982: A History by Renée Haynes (1982, Macdonald & Co (Publishers) Ltd, London).