Ritchie Liquid Compass

Edward S. Ritchie of Boston developed the first successful liquid compass in 1862 and introduced several improvements over the course of the next two decades. This is the model for Ritchie’s third patent (#38,126) dated April 7, 1863. Three features should be noted. The magnetic needle is enclosed in an air-tight metallic case and, with the card, is very nearly the same specific gravity as the liquid. The needle float is in the form of crossed cylinders. And an elastic chamber compensates for the unequal expansion of the liquid and the bowl.
The U.S. Patent Office transferred this compass to the Smithsonian in 1926. Attached to the compass is a Patent Office tag that reads: "No. 38,126 E. S. Ritchie. Mariner’s Compass. Patented Apl 7th 1863."
Ref: "Improved Ship’s Compass," Scientific American 11 (1864): 52.
"The Liquid Compass," Journal of the Franklin Institute 85 (1868): 218-221.
Currently not on view
date made
Ritchie, Edward S.
overall: 3 5/8 in x 5 1/4 in x 7 1/4 in; 9.2075 cm x 13.335 cm x 18.415 cm
place made
United States: Massachusetts, Boston
ID Number
catalog number
patent 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

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