Dip Circle

Description:

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.

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.

Ref: Charles A. Schott, "Terrestrial Magnetism," Report of the Superintendent of the U.S. Coast Survey for 1872, Appendix No. 14, p. 248 and plate 21.

Charles A. Schott, "Terrestrial Magnetism," Report of the Superintendent of the U.S. Coast Survey for 1875, Appendix No. 16, pp. 263-264 and plate 29.

Maker: Henry Barrow & Co.

Location: Currently not on view

Place Made: United Kingdom: England, London

Subject: Science & Scientific Instruments

Subject:

See more items in: Medicine and Science: Physical Sciences, Science & Mathematics, Measuring & Mapping

Exhibition:

Exhibition Location:

Credit Line: U.S. Coast & Geodetic Survey

Data Source: National Museum of American History

Id Number: PH.307207Catalog Number: 307207Accession Number: 65983

Object Name: Dip Circle

Physical Description: metal (overall material)Measurements: circle: 10 1/4 in; 26.035 cmoverall: 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

Guid: http://n2t.net/ark:/65665/ng49ca746a8-e5e0-704b-e053-15f76fa0b4fa

Record Id: nmah_996606

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