Dip Circle

Description
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.

Location
Currently not on view
Object Name
dip circle
maker
Dover
Physical Description
wood (overall material)
metal (overall material)
Measurements
overall: 10 in; 25.4 cm
needle: 3 1/2 in; 8.89 cm
Place Made
United Kingdom: England, London, Charlton
ID Number
PH*327706
accession number
283654
catalog number
327706
subject
Measuring & Mapping
Science & Mathematics
Science & Scientific Instruments
Science & Scientific Instruments
See more items in
Medicine and Science: Physical Sciences
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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