White Azimuth Mirror

William Thomson described a new "Marine Azimuth Mirror" at the 1877 meeting of the British Association for the Advancement of Science, and patented the design in Britain and the U.S.
This instrument is an example of the improved design, with a reflecting prism in place of the original mirror, that Thomson introduced in the early 1880s. It was made before 1892 when Thomson became Lord Kelvin. The inscriptions read "J. WHITE GLASGOW" and "SIR W THOMSON’S PATENT No 2673." The U.S. Naval Observatory transferred it to the Smithsonian in 1966.
Ref: William Thomson, "Device for Taking Azimuths," U.S. Patent #210,068.
William Thomson, "Azimuth Instrument," U.S. Patent #402,364.
Currently not on view
Object Name
azimuth mirror
Thomson, William
White, James
box: 6 3/4 in x 10 1/4 in x 4 7/8 in; 17.145 cm x 26.035 cm x 12.3825 cm
ID Number
catalog number
accession number
Measuring & Mapping
See more items in
Medicine and Science: Physical Sciences
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
U.S. Naval Observatory
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