Accession No

2626

Brief Description

taffrail ship log, Walker's Excelsior IV log, by Thomas Walker and Son Ltd., English, 1940 (c)

Origin

England; Birmingham

Maker

Thomas Walker and Son Ltd.

Class

navigation

Earliest Date

1940

Latest Date

1940

Inscription Date

Material

metal (brass, steel); rope; enamel; glass

Dimensions

one part length 403mm; breadth 155mm; depth 155mm 2nd part length 210mm; breadth 120mm; depth 115mm

Special Collection

Provenance

Purchased from Sotheby’s Belgravia, London, England, 18/07/1980.

Inscription

‘Walker’s
Excelsior IV Log’
‘Made in England by Thos. Walker & Son, Ltd. Birmingham’

Description Notes

Walker’s taffrail log. Brass-cased counter, with mounting ring and attachment for rope. Enamel dial records up to 100 nautical miles, with subsidiary 10 mile dial reading to 1/4 miles. Steel pointers. Hinged glazed cover to dial. Rotator with four fins.

References

Events

Description
Log
A log is used to measure the speed of a ship relative to the surrounding water. Navigation can then be done using “dead reckoning”. The name “log” comes from the original method which involved throwing a log overboard so the relative speeds of the ship and log could be noted. However, by the 17th century, something more accurate was needed.

The first successful self recording log was patented in 1802. It consisted of a spiral moving along the direction of its length, and these revolutions turned a wheel. The speed of rotation of this wheel, and therefore the speed of the ship through water, could then be easily determined and recorded. The harpoon log followed this basic idea and was patented in 1861. The taffrail log did too, but it was easier to read off the dials in this case because, as the name suggests, they were put along the taffrail.

18/10/2002
Created by: Saffron Clackson on 18/10/2002

FM:44391