In 1812 he conducted experiments with Flinders which led to the invention of the Flinders Bar, used for marine compass correction.

Liquid-damped marine compasses for ships and small boats were occasionally used by the British Royal Navy from the 1830s through 1860, but the standard Admiralty compass remained a dry-mount type.

The French astronomer Nicolas Louis de Lacaille first described the constellation as la Boussole (the Marine Compass) and gave Bayer designations to ten stars now named Alpha to Lambda Pyxidis (he skipped the Greek letter iota).

Ritchie thought they could be improved upon, and by 1860 had received a U.S. patent for the first successful and practicable liquid-filled marine compass suitable for general use, a development that has been described as the first major advance in compass technology in several hundred years.

In the latter year, the American physicist and inventor Edward Samuel Ritchie patented a greatly improved liquid marine compass that was adopted in revised form for general use by the United States Navy, and later purchased by the Royal Navy as well.