On the mechanical origin of terrestrial magnetism by Pliny Earle Chase Chase refers to his recent communication with the American Philosophical Society, and his experiments for producing mechanical polarity sufficient to supersede the magnetic polarity of a compass needle, and polarity in the atmosphere. Reference to Edward Sabine’s discussion on the St Helena observations. Discussion on the [table] of solar diurnal variation in the magnetic force at St Helena, and includes a table depicting the differences and ratios in each quadrant. Chase requests Sabine to present this information to the next meeting of the Royal Society. 28 September 1864