An 18th-Century English brass alt-azimuth theodolite,

Details

An 18th-Century English brass alt-azimuth theodolite,
signed Heath & Wing LONDON, the vertical semi-circle mounted off-centre and supporting the telescope which is moved by rack and pinion wheel, and divided into two quadrants 0-90°, with inner scales marked for Feet Links, the horizontal scale divided by each degree 0-360° read by a vernier scale and rotated by rack-work and held by a clamping screw, the well-engraved and silvered compass dial with spirit level and original needle with pyramid agate pivot point, underneath are four levelling screws and the attachment point to the original tripod -- 61in. (155cm.) high, with accompanying mahogany case -- 9.3/8in. (23.8cm.) wide

See Colour Illustrations

Literature

BENNETT, Dr J.A., The Divided Circle (Oxford, 1987) pp.146-147, ill.103
CLIFTON, Dr G., Directory of British Scientific Instrument Makers, 1550-1851 (London, 1995)

Lot Essay

Thomas Heath, Mathematical Instrument Maker, was apprenticed to Benjamin Scott in 1712. He worked by himself from 1720 to 1753 and was Free of the Worshipful Company of Grocers by 1720. This particular model of theodolite was developed by him from 1740 and first published by John Hammond in The Practical Surveyor. That same year, Tycho Wing joined Heath as a junior partner. By 1750 the instrument is fully described as 'a survey completed by the new improved Theodolite'. A very similar instrument is in the collection of the Whipple Museum of the History of Science, Cambridge, England.

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