Log and Rotor, Patent Model
date: label: Date made
content: 1881
label: patent date
content: 1881-02-22
name: label: patentee
content: Walker, Thomas F.
notes: label: Description
content: 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.
label: Description
content: Speed is an important factor in accurate navigation, and, since the sixteenth century, sailors had determined a vessel's speed using a log. This device was basically a rope with knots tied at intervals along its length. With a board attached to one end to create drag, the log-line would be heaved overboard and allowed to run out for a short period of time. The number of knots counted off indicated the speed. (The unit of speed at sea is therefore the knot, one knot being equal to one nautical mile per hour). Logs were susceptible to a variety of errors, so instrument makers developed mechanical logs to improve the recording of speed and distance.
label: Description
content: Thomas Walker (1805-73) was a nephew of Edward Massey, the London nautical instrument maker whose patent mechanical logs enjoyed wide use in the nineteenth century. Walker's firm and Massey's merged at the end of the century. The Walker log seen here was patented in the United Kingdom (British patent no. 4,369, Oct. 30, 1878) before it received similar protection in the United States.
label: Location
content: Currently not on view
topic: label: Subject
content: Patent Models
setName: label: See more items in
content: Work and Industry: Maritime
label: See more items in
content: America on the Move
label: See more items in
content: Transportation
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: TR.308558
label: catalog number
content: 308558
label: accession number
content: 89797
label: patent number
content: 238187
objectType: label: Object Name
content: Log, Taffrail
label: Object Name
content: log, taffrail, patent model
label: Object Name
content: patent model, log, taffrail
label: Object Type
content: Patent Model
label: Other Terms
content: Log, Taffrail; Maritime; Ship
physicalDescription: label: Physical Description
content: brass (overall material)
label: Measurements
content: overall: 9 1/2 in; 24.13 cm