Steur Holland Circle

Description
Jacob de Steur, who worked in Leyden in the second half of the 17th century, is known to have made several instrument of this sort. This one is particularly elegant, with images of dolphins at either side of the four fixed sights, and four dolphins on the alidade. The outer circle is graduated to 15 minutes. One half of the inner circle has a grad or gradient scale (graduated 0–100–0–100–0 in equal units) as used by military engineers. The other half has two irregular scales. One is a polygonal scale marked "anguli centri." It is numbered from 3 to 12, and is designed for laying out the exterior angles of forts with 3 to 12 sides. The other irregular scale is marked "mechanica." It bears the maker’s mark "Jacobus de Steur Fecit Leyde." The bottom drawer of the wooden box contains several auxiliary items: a sighting bar that can fit over the sights on the alidade; a pair of tall sight vanes that can fit over any of the shorter vanes; a head for a jacob's staff; two joints with screw bases (one fixed and the other universal); and a clinometer bob. There are spaces for two other accessories, now lost.
Location
Currently not on view
Object Name
holland circle
maker
Steur, Jacob de
Measurements
overall: 11 in; 27.94 cm
needle: 2 1/4 in; x 5.715 cm
sighting bar: 11 in; 27.94 cm
place made
Nederland: Zuid-Holland, Leiden
ID Number
PH*317346
accession number
230279
catalog number
317346
subject
Measuring & Mapping
Surveying and Geodesy
See more items in
Medicine and Science: Physical Sciences
Surveying and Geodesy
Data Source
National Museum of American History, Kenneth E. Behring Center

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