Rotterdam, Bataafsch Genootschap der Proefondervindelijke Wijsbegeerte te Rotterdam, 1919. 4to (26.0 x 22.0 cm). 25 [49] pp.; 12 text figures. Later quarter cloth over original printed wrappers (society's logo printed on rear wrapper).

A rare paper in which Lorentz explains (the history of researches in) electromagnetism and gravity to a Dutch audience. It forms the most substantial part of a publication commemorating the 150th anniversary - in 1919 - of a Dutch society of applied philosophy which still exists today. This work is not included in the Verslag der voordrachten van leden van het Bataafsch Genootschap Bundel I (1914-1920)[ Report of the lectures of members of the society between 1914-1920], although it was published by this society. Small chip to the front wrapper lower outer corner; cancelled stamp in front cover lower margin and title page blank verso; shallow blind stamp in the lower margin, and ink number in the top margin of the title page. Otherwise unmarked, with the Lorentz paper clean.