Dip Circle

The U.S. Naval Observatory acquired this instrument around 1887, in preparation for a new program in terrestrial magnetism. It is a Kew pattern dip circle--that is, of the type used at the Kew magnetic observatory in England. It is marked "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.

Ref: Charles A. Schott, "Terrestrial Magnetism," Report of the Superintendent of the U.S. Coast Survey for 1875, Appendix 16, plate 29b.

J. A. Hoogewerff, "Magnetic Observations Made at the United States Naval Observatory, 1888 and 1889," Observations Made During the Year 1886 at the United States Naval Observatory, Appendix 1, p. 2.

Currently not on view
Object Name
dip circle
Physical Description
wood (overall material)
metal (overall material)
overall: 10 in; 25.4 cm
needle: 3 1/2 in; 8.89 cm
Place Made
United Kingdom: England, London, Charlton
ID Number
accession number
catalog number
Science & Scientific Instruments
Science & Scientific Instruments
See more items in
Medicine and Science: Physical Sciences
Measuring & Mapping
Science & Mathematics
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
U.S. Department of Defense, Dept. of the Navy, U.S. Naval Observatory

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