Dip Circle
name: label: maker
content: Henry Barrow & Co.
notes: label: Description
content: Soon after becoming Superintendent of the U.S. Coast Survey in 1843, Alexander Dallas Bache ordered a dip circle from Henry Barrow (1790-1870), the leading producer of geomagnetic instruments in England at the time. The Survey went on to purchase several more Barrow circles of this sort and was still using them in the 1870s.
label: Description
content: This example is marked "Henry Barrow & Co., 26 Oxendon Street, London" and "CS 9." It is based on the form that Henri P. Gambey of Paris introduced in the 1830s. The needle is long, stretching from one side of the vertical circle to the other. The vertical circle is housed within the wood and glass box, graduated to about 15 minutes, and read by opposite magnifiers. The horizontal circle is graduated and read by vernier.
label: Description
content: Ref: Charles A. Schott, "Terrestrial Magnetism," <i>Report of the Superintendent of the U.S. Coast Survey for 1872,</i> Appendix No. 14, p. 248 and plate 21.
label: Description
content: Charles A. Schott, "Terrestrial Magnetism," <i>Report of the Superintendent of the U.S. Coast Survey for 1875,</i> Appendix No. 16, pp. 263-264 and plate 29.
label: Location
content: Currently not on view
place: label: place made
content: United Kingdom: England, London
topic: label: Subject
content: Science & Scientific Instruments
setName: label: See more items in
content: Medicine and Science: Physical Sciences
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content: Science & Mathematics
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content: Measuring & Mapping
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.307207
label: catalog number
content: 307207
label: accession number
content: 65983
objectType: label: Object Name
content: Dip Circle
physicalDescription: label: Physical Description
content: metal (overall material)
label: Measurements
content: circle: 10 1/4 in; 26.035 cm
label: Measurements
content: overall: 14 7/8 in x 14 3/4 in x 8 1/2 in; 37.7825 cm x 37.465 cm x 21.59 cm