Graphometer

Description:

A graphometer consists of a graduated semicircle with a pair of sight vanes at either end, and a movable alidade with another pair of sights at either end. The form was introduced in Philippe Danfrie, Déclaration de l’usage du graphomètre (Paris, 1597), and was always popular in France. Many graphometers have an inset magnetic compass. Most are made of brass, but some American ones are made of wood. Some 19th-century examples had telescopes rather than open sights. Graphometers were also known as semi circles or semicircumferentors.

Samuel P. Langley, the third Secretary of the Smithsonian, bought this graphometer for the U.S. National Museum in 1902. The semicircle is graduated to single degrees, numbered clockwise and counterclockwise, and read by diagonal scales at either end of the alidade to 10 minutes. The "Delure A Paris" inscription indicates that it was made in the early 18th century.

Ref: J. A. Bennett, The Divided Circle (Oxford, 1987), pp. 49–50.

Maker: Delure

Location: Currently not on view

Place Made: France: Île-de-France, Paris

See more items in: Medicine and Science: Physical Sciences, Surveying and Geodesy, Measuring & Mapping

Exhibition:

Exhibition Location:

Data Source: National Museum of American History

Id Number: PH.219497Catalog Number: 219497Accession Number: 40529

Object Name: Graphometer

Measurements: overall: 9 1/2 in; 24.13 cmneedle: 1 1/2 in; 3.81 cmoverall: 6 3/4 in x 9 3/4 in x 6 3/4 in; 17.145 cm x 24.765 cm x 17.145 cm

Guid: http://n2t.net/ark:/65665/ng49ca746a5-9a3b-704b-e053-15f76fa0b4fa

Record Id: nmah_748073

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