Object Details
- Description
- 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.
- 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.
- 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
- Data Source
- National Museum of American History
- maker
- Dover
- Dover, John
- Credit Line
- U.S. Department of Defense, Dept. of the Navy, U.S. Naval Observatory
- Physical Description
- wood (overall material)
- metal (overall material)
- Measurements
- overall: 10 in; 25.4 cm
- needle: 3 1/2 in; 8.89 cm
- 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
- Object Name
- dip circle
