Beschreibung:

A brass heliochronometer Pilkington and Gibbs Limited, Preston; retailed by James Brown Glasgow, early 20th century The angled rotating plate with fixed backsight and pinhole foresight adjusted via a disc calibrated for the date to allow a reading for mean time to be taken from the circumference via a sector divided for minutes against a movable hour scale, the mechanism mounted onto a cast brass bowl fixed via an adjustable pivot for setting latitude onto a moulded disc base, the date setting dial stamped JAMES BROWN OPTICIAN, 78 ST. VINCENT STREET,. GLASGOW and the leading edge of the rim engraved PILKINGTON & GIBBS LTD. PRESTON ENGLAND over serial number 367 to circumference, 22.5cm (9ins) diameter. The current lot is made to a design patented by George James Gibbs on 14th February 1907 in response to general demand for a method of setting clocks to Greenwich Mean Time (which had been adopted by the UK by Act of Parliament in 1880). In order to be able to realise the potential of his invention Gibbs entered into partnership with William Renard Pilkington to manufacture the heliochronometer primarily for retail by leading scientific instrument suppliers such as Negretti and Zambra. The firm produced the instrument from 1907 until 1914 when it is thought production ceased due to the outbreak of WWI. Key to the instrument’s operation is the incorporation of a shaped cam to adjust the foresight to compensate for the difference in solar and mean time. When properly set up the instrument will provide readings accurate to the nearest minute. Condition report disclaimer