For pt.XVI see ibid., vol.9, no.3, p.21 et seq. (1993). Early investigations into partial discharge (PD) phenomena are reviewed to illustrate how little has changed and how much has, in some respects, been repeated during the forty years from 1940 to 1980. The early days of PD research included studies of PD in gas-filled cavities in oil-impregnated paper insulation, broad studies of PD in high voltage apparatus and dielectric materials, and research into PD in turbine generator insulation systems. The development of PD test techniques, development of test apparatus, and development of PD-related standards are discussed. >