Excelsior Mark IV Traffail ship's log

Maker Walker and Son

Date20th century

Object number00029319

NameLog rotator

MediumRope, brass

DimensionsOverall: 80 x 80 x 80 mm, 2.15 kg

ClassificationsTools and equipment

Credit LineANMM Collection Gift from Dorothy Sharp

Terms

DescriptionThis Excelsior Mark IV ship's log was designed by Walker and Son. The log consists of a cylindrical rotator with four fins, which is attached to a rope 100 feet (20.5 meters) long. The other end of the rope has a brass hook which is attached to the register (00029320). As the log is pulled through the water, the fins turn causing a series of gears to turn. These turns are recorded and interpreted as the vessel's speed and distance travelled.HistoryA log is the name given to any device for measuring the speed of a vessel though water or the distance the vessel has sailed in a given time. Originally logs were simple affairs, but with the growth of sea-borne trade in the 17th and 18th century the need for more accurate measurements of a ship’s speed became more widespread. A name synonymous with the development of the log is Thomas Walker (1805 - 1873), an English clockmaker who began working for his uncle under Edward Massey in 1850 making logs and sounders under his uncle’s patent. In 1861 Walker founded a company with his son Alexander and patented a revolutionary mechanical ship's log called the Harpoon, which incorporated the dials into the outer casing of the rotor. In 1863, a new model, the A1 Harpoon, was produced soon to be followed by the A2 Harpoon in 1866. In 1879, Walker and Son invented the Traffail log which allowed readings to be taken without the removal of the log from the water and superseded all the harpoon-type logs. SignificanceThe invention of the Traffail log by Walker and Son in 1879 was an important development ship’s logs. The Traffail log allowed readings to be taken without the removal of the log from the water, which saw it superseded earlier harpoon-type logs.