Dip Circle
name: label: maker
content: U.S. Coast and Geodetic Survey
notes: label: Description
content: This Kew pattern dip circle is marked "U.S.C.&G.S. No. 23" and was probably made in the instrument shop of the U.S. Coast and Geodetic Survey. The vertical circle is silvered, graduated to 30 minutes, and read by opposite verniers and magnifiers to single minutes. The horizontal circle is graduated to 30 minutes and read by vernier to single minutes. On top of the box there is a compass needle in a box with peep sights that measures magnetic variation.
label: Description
content: A brass housing on the front of the instrument holds an auxiliary needle (now missing) that serves as a deflector for the determination of total intensity; this technique was introduced by Humphrey Lloyd, professor of natural philosophy at Trinity College, Dublin, in the early 1840s.
label: Description
content: Ref: Daniel Hazard, <i>Directions for Magnetic Measurements</i> (Washington, D.C., 1911), pp. 66-69.
label: Description
content: Humphrey Lloyd, "On a New Magnetical Instrument, for the Measurement of the Inclination, and Its Changes," <i>Proceedings of the Royal Irish Academy</i> 2 (1840-1844): 210-217, 226-232.
label: Location
content: Currently not on view
place: label: Place Made
content: United States: District of Columbia, Washington
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.314632
label: accession number
content: 208213
label: catalog number
content: 314632
objectType: label: Object Name
content: dip circle
physicalDescription: label: Physical Description
content: metal (overall material)
label: Measurements
content: overall: 10 1/2 in; 26.67 cm
label: Measurements
content: overall in case: 12 in x 9 3/8 in x 8 1/4 in; 30.48 cm x 23.8125 cm x 20.955 cm