box: 6 13/16 in x 10 1/4 in x 4 3/4 in; 17.30375 cm x 26.035 cm x 12.065 cm
overall: 9 in x 6 in x 2 in; 22.86 cm x 15.24 cm x 5.08 cm
overall: 6 3/4 in x 10 1/4 in x 4 3/4 in; 17.145 cm x 26.035 cm x 12.065 cm
Object Name:
azimuth mirror
Place made:
United Kingdom: Scotland, Glasgow
Date made:
early 20th century
Description:
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. Thomson introduced this form in the early 1880s. The signature indicates that it was made during the period 1900-1913. The base bears the inscriptions "KELVIN & JAMES WHITE, LIMITED. GLASGOW" and "LORD KELVIN’S (SIR WM THOMSON) PATENTS No 5713." The U.S. Coast & Geodetic Survey transferred the instrument to the Smithsonian in 1929.
Ref: William Thomson, "Device for Taking Azimuths," U.S. Patent #210,068.
William Thomson, "Azimuth Instrument," U.S. Patent #402,364.
