Holland Circle
date: label: date made
content: 1622
name: label: maker
content: Secoes, Jacob
notes: label: Description
content: In the late 16th century, a Dutch scholar and instrument maker named Gemma Frisius suggested that a good surveying instrument could be made by attaching a magnetic compass to the back of an astrolabe. Building on this idea, Jan Dou designed an instrument with two pairs of fixed sights attached to a graduated circle, and another pair of sights attached to either end of a movable alidade. Dou published an account of this instrument in Dutch in 1612, and the form became popular with surveyors in the Netherlands. The name Holland Circle was coined in the 19th century. The Holland Circle is similar to but easily distinguishable from the common theodolite.
label: Description
content: The outer circle of this example is graduated every thirty minutes, and has additional scales for tangents, sines, and secants. The small compass in the center has a fleur–de–lis at north, and an offset line probably indicating magnetic variation. Inscriptions read "JACOB SECOES" and "ANNO 1622."
label: Description
content: Ref: Jan Pietersz. Dou, Tractaet vant maken ende Gebruycken eens nieu gheordonneerden Mathematischen Instruments (1612).
label: Description
content: H. C. Pouls, De landmeter Jan Pietersz. Dou en den Hollandsce Circle (Delft, 2004).
label: Location
content: Currently not on view
place: label: place made
content: Netherlands: Holland
setName: label: See more items in
content: Medicine and Science: Physical Sciences
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content: Trigonometry
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content: Surveying and Geodesy
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content: Measuring & Mapping
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: PH.317347
label: catalog number
content: 317347
label: accession number
content: 230279
objectType: label: Object Name
content: holland circle
physicalDescription: label: Measurements
content: overall: 9 3/8 in; 23.8125 cm
label: Measurements
content: overall in case: 4 5/16 in x 11 in x 11 1/4 in; 10.95375 cm x 27.94 cm x 28.575 cm