Log and Rotor, Patent Model
From the collection of National Museum of American History. Free to download, adapt and use — no permission needed.
This mechanical log measures a vessel's speed moving though water. The four-bladed rotator is towed astern. As it spins, the rotations of the towing line are registered by a wheel works and dial mounted to the vessel's rail. Older mechanical logs had placed the counting mechanism next to the rotator, requiring the log to be hauled in for reading. In the 1860s American and then English makers began placing the dial in a separate housing on the ship's rail, which allowed readings while the log was in use. Thomas Walker's firm in Birmingham, England, was a leading maker of logs, and he submitted this example, with its special rope connector and numerous internal improvements, to the U.S. Patent Office in 1877.
National Museum of American History’s own description
