I am much indebted to Commander W. E. May for calling my attention to the numerous references to George Margetts (see this Journal, 6, 403) in The Marine Chronometer by R. T. Gould (J. D. Potter, 1923). The following extracts from this book will provide some of the biographical information which I was unable to give previously. ‘George Margetts (1748–1804), already referred to as the inventor of a form of lever escapement, produced several machines of this kind.’ (Namely chronometers showing sidereal and mean time.)