Theodolite
notes: label: Description
content: This theodolite was probably made in London in the mid-18th century. Its basic form-with the telescope mounted on the curved side of a semicircle-derives from the design that Thomas Heath introduced in 1725. The horizontal circle and vertical arc are graduated every degree and read by verniers to 10 minutes. The words "Diff: Hypo & Base" on the telescope support and the scales labeled "Feet" and "Links" on the vertical arc are used to correlate angle of elevation or depression with horizontal distances. In addition to the telescope, there is a pair of open sight vanes. A level vial is mounted above the telescope.
label: Description
content: This theodolite belonged to Orange Ellis, a surveyor who lived in Odelltown, a village along the Richelieu River, a few miles north of New York State. Odelltown was settled by Joseph Odell, a Loyalist from Poughkeepsie who moved from the United States to Lower Canada in 1788, in order to remain under British rule. Odelltown was later seen as a Britannic outpost in a Francophone region of Quebec.
label: Description
content: Ref: J. A. Bennett, <i>The Divided Circle</i> (Oxford, 1987), pp. 86, 146-147.
label: Location
content: Currently not on view
place: label: place made
content: United Kingdom: England, London
setName: label: See more items in
content: Medicine and Science: Physical Sciences
label: See more items in
content: Surveying and Geodesy
label: See more items in
content: Measuring & Mapping
publisher: label: Related Publication
content: Bennett, J. A.. Divided Circle. A History of Instruments for Astronomy, Navigation and Surveying
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: PH.309596
label: accession number
content: 104762
label: catalog number
content: 309596
objectType: label: Object Name
content: theodolite
physicalDescription: label: Measurements
content: overall: 7 1/2 in; 19.05 cm
label: Measurements
content: horizontal circle: 5 1/2 in; 13.97 cm
label: Measurements
content: needle: 2 1/2 in; 6.35 cm
label: Measurements
content: telescope: 7 1/2 in; 19.05 cm
label: Measurements
content: overall: 8 1/8 in x 7 1/4 in x 5 7/8 in; 20.6375 cm x 18.415 cm x 14.9225 cm