Threlfall quartz-thread gravity balance for exploration geophysics, made by Richard Threlfall and James Pollock, Australia, 1889 - 1899, later tested and modified at the National Physical Laboratory, Teddington, London, UK, 1923. Threlfall quartz-thread gravity balance 1899
Main body of Threlfall quartz-thread gravity balance, 1899. Mounted on wood. Main body of Threlfall gravity balance