Further history of a quartz thread gravity balance

A former paper* by one of the present authors and JAMES ARTHUR POLLOCK contains an account of the construction of a quartz thread gravity balance which was made at the University of Sydney during the time R. THRELFALL was Professor of Physics there. This work extended from 1889 up to the time of publication, and included an account of a good many gravimetric observations at Sydney, Melbourne, Hobart, and at various places in New South Wales. Final tests were made by taking the balance to and fro between Sydney and Hornsby, which is near Sydney but is 592 feet above sea-level, the University of Sydney, which was the Sydney observation station, being only slightly above sea-level (120 feet). As the result of several such journeys we finally felt entitled to say that “ We have therefore determined the value of g at Hornsby relatively to that at Sydney in three journeys with a maximum difference of 0.4 sextant minutes, or to less than 1 part in 500,000 in the value of g ." It had been intended to embark on a series of observations on the Australian coast, but, unfortunately, R. THRELFALL returned to England in 1898 and arrangements for carrying on the work had to be considered. J. A. POLLOCK succeeded R. THRELFALL as Professor of Physics at the Sydney University, and it was arranged that the balance, which, by the way, had been exhibited at the British Association Meeting at Dover, should be in J. A. POLLOCK’s charge and that he should continue the work in so far as his new duties as Professor of Physics enabled him to do so. Unfortunately, an opportunity never occurred and the balance was stored in one of the cellars of the Physical Laboratory of the University till 1923. Meanwhile Professor POLLOCK died.