Theodolite
name: label: maker
content: Gilbert, John
label: maker
content: Gilbert, John
notes: label: Description
content: This theodolite belonged to John Johnson (1771-1841), the surveyor general of Vermont. Its basic form-with the telescope mounted on the open side of a semicircle-derives from the design that Jonathan Sisson introduced in London in 1737. The horizontal circle and vertical arc are graduated every degree and read by vernier to 10 minutes. The vertical arc has a second scale marked "LINKS of CHAINS" that correlates angle of elevation with horizontal distances, to be used when surveying sloping ground. The level vial on the compass face seems to be original with the instrument; the vial outside the compass may be a later addition.
label: Description
content: The "J. Gilbert Tower Hill LONDON" inscription refers to either the John Gilbert who worked in London in the years 1719-1750, or his son of the same name who worked in London in the years 1751-1791.
label: Description
content: Ref: Gloria Clifton,<i>Directory of British Scientific Instrument Makers 1550-1851</i> (London, 1995), p. 112.
label: Description
content: "John Johnson" in Abby M. Hemenway, ed., <i>The Vermont Historical Gazeteer</i> (Burlington, Vt., 1868), vol. 1, pp. 596-599.
label: Description
content: "John Johnson" in <i>National Cyclopaedia of American History</i>, vol. 17, pp. 290-291.
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: Clifton, Gloria and Gerard L. E. Turner. Directory of British Scientific Instrument Makers 1550-1851
label: Related Publication
content: Hemenway, Abbey Maria. Vermont Historical Gazetteer
label: Related Publication
content: National Cyclopedia of American History
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: PH.309545
label: accession number
content: 95588
label: catalog number
content: 309545
objectType: label: Object Name
content: theodolite
physicalDescription: label: Measurements
content: horizontal circle: 10 in; 25.4 cm
label: Measurements
content: overall: 8 1/2 in; 21.59 cm
label: Measurements
content: needle: 3 1/4 in; 8.255 cm
label: Measurements
content: telescope: 12 1/2 in; 31.75 cm
label: Measurements
content: hanging level: 4 in; 10.16 cm
label: Measurements
content: overall in case: 11 3/8 in x 15 5/8 in x 11 3/4 in; 28.8925 cm x 39.6875 cm x 29.845 cm