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) of 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. 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. An attached Patent Office tag 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.

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