Dip Circle
name: label: maker
content: Dover
label: maker
content: Dover, John
notes: label: Description
content: This is a Kew pattern dip circle--of the type used at the Kew magnetic observatory in England--inscribed "Dover, Charlton Kent. Circle No. 85." It has a short needle placed inside a wooden box with glass faces; a vertical circle placed on the outside of the box that is read by verniers and magnifiers; and two other magnifiers for viewing the ends of the needle. The vertical circle is silvered, graduated to 30 minutes, and read by opposite verniers and magnifiers to single minutes. The horizontal circle is silvered, graduated to 30 minutes, and read by vernier to single minutes. The U.S. Naval Observatory acquired this instrument around 1887, for a new program in terrestrial magnetism.
label: Description
content: John Dover (1824-1881) began in business in London in 1841; by 1869 he had moved to Charlton, in the County of Kent. His son continued the firm.
label: Description
content: Ref: Charles A. Schott, "Terrestrial Magnetism," <i>Report of the Superintendent of the U.S. Coast Survey for 1875,</i> Appendix 16, plate 29b.
label: Description
content: J. A. Hoogewerff, "Magnetic Observations Made at the United States Naval Observatory, 1888 and 1889," <i>Observations Made During the Year 1886 at the United States Naval Observatory</i>, Appendix 1, p. 2.
label: Location
content: Currently not on view
place: label: Place Made
content: United Kingdom: England, London, Charlton
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. Department of Defense, Dept. of the Navy, U.S. Naval Observatory
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: PH.327706
label: accession number
content: 283654
label: catalog number
content: 327706
objectType: label: Object Name
content: dip circle
physicalDescription: label: Physical Description
content: wood (overall material)
label: Physical Description
content: metal (overall material)
label: Measurements
content: overall: 10 in; 25.4 cm
label: Measurements
content: needle: 3 1/2 in; 8.89 cm
label: Measurements
content: overall: 10 1/2 in x 7 3/4 in x 7 1/2 in; 26.67 cm x 19.685 cm x 19.05 cm