Arnold (John): An Account kept during thirteen months in the Royal Observatory at Greenwich of the Going of a Pocket Chronometer, made on a new construction, London, sold by John Arnold, 1780, 4to, 6pp. -- A Letter from M. Christian Mayer, Astronomer to the Elector Palatine, to Mr. N.N. on the Going of a New Pendulum Clock made by John Arnold, and set up in the Elector's Observatory at Manheim, London, for T. Becket, 1781, 4to, 28pp. -- Whitehurst (John): An Attempt towards obtaining Invariable Measures of Length, Capacity, and Weight, from the Mensuration of Time, independent of the Mechanical Operations requisite to ascertain the Center of Oscillation, Or the True Length of Pendulums, London, for the Author and sold by William Bent, 1787, 4to, 47pp., 3 folding engraved plates, together 3 pamphlets, disbound. (3)