Ritchie Liquid Compass

This compass–with six needles, and a flat card with central buoyancy–was Ritchie’s most successful design and was widely used by American merchant ships and the U.S. Navy. The Ritchie ledgers, now held by Ritchie Navigation, indicate that this example was manufactured on Jan. 5, 1873 and sold to one L. J. Sloane. The U.S. Coast & Geodetic Survey acquired it in 1914, and transferred it to the Smithsonian in 1929. The inscriptions read "E. S. RITCHIE BOSTON. PATENTED SEPT. 9, 1862. APL. 7, 1863. MAY 12, 1868. July 19, 1870" and "6937" and "U.S.C.&G.S."
Ritchie’s patent of Sept. 9, 1862 (#36,422) described a liquid compass so designed that the liquid would not oxidize the magnet or card, and that the friction and wear of the pivot and its bearing was minimized. Ritchie obtained two patents on April 7, 1863. One (#38,125) described a needle enclosed in an air-tight metallic case; the other (#38,126) described a liquid compass that could be read at a distance so it would not be affected by any iron on or about the deck of a ship. Ritchie’s patent of May 12, 1868 (#77,763) described a paint that would not deteriorate in the liquid in the compass. His patent of July 19, 1870 (#105,492) described a way to hold the glass in place with a water-tight joint..
Ref: E. S. Ritchie & Sons, Ritchie’s Liquid Compasses and Nautical Instruments (ca. 1905).
T. S. & J. D. Negus, Illustrated Catalogue of Nautical Instruments (New York, n.d.), p. 204.
Currently not on view
Object Name
liquid compass
date made
Ritchie, Edward S.
bowl: 7 1/2 in; 19.05 cm
card: 6 1/2 in; 16.51 cm
place made
United States: Massachusetts, Boston
ID Number
catalog number
accession number
See more items in
Medicine and Science: Physical Sciences
Measuring & Mapping
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
U.S. Coast & Geodetic Survey

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