Dip circle used to study the earth's magnetic field at Parramatta Observatory
Object No. H7507
This dip circle or inclinometer almost certainly came from the Parramatta Observatory where it was used for studying the Earth's magnetic field. It is listed in the 1825 and 1847 lists of Parramatta instruments as well as being mentioned in research papers on magnetism by observatory staff. A dip circle measures the inclination of the Earth's magnetic field compared with the horizontal. In contrast a magnetic compass points horizontally, but the magnetic field is only horizontal at the equator. The higher the latitude the more magnetic field points downwards. Dip circles were used in surveying, mining and studying the Earth's magnetic field. For accurate readings the instrument had to be carefully constructed. Henri Prudence Gambey was the best known French maker of geomagnetic instruments. Accordingly, this instrument is carefully made with attention to the reduction of friction in the pivoting of the magnetic needle: on depressing a lever, the needle pivots on a pair of jewels on either side to reduce friction. Dr Nick Lomb, Curator of Astronomy, April 2009
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Summary
Object Statement
Inclinometer (also called dip circle or dipping compass), metal / wood / glass, made by Gambey à Paris, Paris, France, [1815-1818]
Physical Description
An inclinometer used to indicate the vertical direction of the earth's magnetic field. The inclinometer or dip circle consists of a horizontal circle with a graduated scale engraved on its surface. The horizontal circle is fixed to a tripod with adjustable legs. A brass platform attached to the horizontal circle supports a brass level and a vertical brass frame. The level has a glass window in the top through which liquid can be viewed. One side of the level has corroded and become detached from the brass plate. The vertical frame holds a vertical circle with a graduated scale engraved around its edge. Balanced in the centre of the frame is a needle that is pointed at both ends. A square wooden and glass frame surrounds the circle of the inclinometer. Observatory stock number 212.
DIMENSIONS
Height
375 mm
Width
340 mm
Depth
225 mm
PRODUCTION
Notes
The inclinometer was made by Henri Prudence Gambey in Paris, France between 1815 and 1818.
HISTORY
Notes
Sir Thomas Brisbane who founded Parramatta Observatory spent 1815 to 1818 in Paris with Wellington's victorious army after the Battle of Waterloo. During that time he purchased the Breguet and Sons clock H9890, another important item that he eventually brought to Parramatta. It is likely that Brisbane purchased the Gambey dip circle at that time as well. The Gambey dip circle came with other Parramatta Observatory instruments to Sydney Observatory in 1858 but it's association with the historic Parramatta Observatory was forgotten when Sydney Observatory disposed of the old and unused instrument to the NSW Government Stores in 1964. In turn Government Stores transferred the equipment to the Museum of Applied Arts and Sciences but no history or provenence was recorded. The association was rediscovered in 2009 when a member of the public, Ms Sharon Rutledge, who had studied Parramatta Observatory, contacted Dr Nick Lomb, Curator of Astronomy with information that a Gambey dip circle had been listed in the 1825 and 1847 lists of Parramatta instruments as well as being mentioned in research papers on magnetism by observatory staff. (See article 'Meet Sydney's nurse to the stars', by Deborah Smith, Sydney Morning Herald, 2009, April 19)
SOURCE
Credit Line
Gift of Government Stores Department, 1964
Acquisition Date
30 June 1964
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