Zenith Telescope
name: label: maker
content: Troughton and Simms
notes: label: Description
content: Zenith telescope marked "Troughton & Simms, London, 1849" and "U. S. C. S. Z. T. No. 4.” This, the last of four zenith telescopes that Troughton & Simms made for the U. S. Coast Survey, arrived in the United States in 1849, and was used for the determination of latitude by the Talcott method. .
label: Description
content: When the Survey agreed join in the variation of latitude (polar motion) program organized by the International Geodetic Association, and found that no other instruments were available, it decided to have zenith telescopes No. 2 and No. 4 "remodeled at the Survey Office." Edwin Smith, chief of the Instrument Division, explained that "every precaution" was taken to make these instruments "as perfect as possible under the circumstances." The new features included: base and leveling screws; vertical axis; wyes for horizontal axis of telescope, with adjustment for level; larger horizontal axis for the telescope; new micrometer screw and reconstruction of micrometer box and slide; improved clamp to telescope; two fine levels attached to telescope; and a striding level for the telescope axis. The whole instrument was polished and bronzed, and provided with electric lamps and batteries "for illumination of telescope field, the reading of levels, etc." Zenith telescope No. 2 was used in Hawaii in 1891–1892, while zenith telescope No. 4 was used at Rockville, Md.
label: Description
content: Ref: [E. Smith], "On the Variation of Latitude at Rockville, Md., as Determined from Observations Made in 1891 and 1892 in Cooperation with the International Geodetic Association," <i>United States Coast and Geodetic Survey Report for 1892</i>, Appendix No. 1, pp. 4–5, with illustration.
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
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content: Surveying and Geodesy
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content: Measuring & Mapping
publisher: label: Related Publication
content: United States Coast and Geodetic Survey Report for 1892
creditLine: label: Credit Line
content: U. S. Coast & Geodetic Survey
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: PH.316660
label: catalog number
content: 316660
label: accession number
content: 226636
objectType: label: Object Name
content: zenith telescope
physicalDescription: label: Measurements
content: overall: 55 in x 20 in x 17 3/4 in; 139.7 cm x 50.8 cm x 45.085 cm