LOCKE, John, physicist, born in Fryeburg, Maine, 19 February, 1792; died in Cincinnati, Ohio, 10 July, 1856. He was graduated at the medical department of Yale in 1819, and afterward became geologist on the U, S. explorations of the northwest territories and on the state survey of Ohio. For many years after 1836 he was professor of chemistry in the Medical college of Ohio. Professor Locke was one of the pioneers in the sciences of botany, geology, and electricity, making many discoveries in these branches, especially in terrestrial magnetism, he made various improved and original instruments for use in optics, physics, electricity, and magnetism, among which were the gravity escapement for regulator clocks (1844), which has never been surpassed, and his electro-chronograph (1848), subsequently purchased for the United States naval observatory at an expense of $10,000; also a spirit-level (1850), which is still in use among civil engineers. Professor Locke contributed to the proceedings of various scientific societies and to the "American Journal of Science," and published text books on botany and on English grammar.