Regular clock made by John Shelton, 1768: Cook's second and third voyages. The property of The Royal Society. Card No. 258

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Regular clock made by John Shelton, 1768: Cook's second and third voyages. The property of The Royal Society. Card No. 258

Printer E Baylis & Son (British, 1858 - 2003)

Date1920-1940

Object number00000377

NamePostcard

MediumInk on paper

DimensionsOverall: 105 x 150 mm

ClassificationsPosters and postcards

Credit LineANMM Collection

Terms

DescriptionA postcard showing the regulator clock made by John Shelton in 1768 that was used on Cook's second and third voyages. The clock is the property of the Royal Society.History"The long-case astronomical regulator, made by John Shelton, that features in the exhibition was carried by Cook aboard the RESOLUTION on both his second and third voyages to the South Seas. Regulators were accurate clocks used specifically for timing astronomical events, such as transit observations, to the exact second; this regulator is one of five created by Shelton for the Royal Society for the purpose of timing the transits of Venus in 1761 and 1769. The regulator measures sidereal time (time measured from the apparent movement of the stars) instead of solar time (time measured from the apparent movement of the sun). In 1828 this regulator was used to compare the strength of gravity at both the top and bottom of a mine in an attempt to find the density of the Earth. While the regulator was extremely accurate, it could only be used on land. Until John Harrison produced his chronometer H4 in 1759, no simple and effective method existed for accurately calculating longitude at sea. " [http://www.nma.gov.au/exhibitions/exploration_and_endeavour/voyages_resolution] SignificanceThe long-case astronomical regulator, made by John Shelton, was carried by Cook aboard HMS RESOLUTION on both his second and third voyages to the South Seas.