Historical information

Navigators use parallel rule with maps and charts for plotting a specific course on a chart. One long edge is used with the compass rose on the chart, aligning the centre of the rose with the desired direction around the edge of the rose. The compass bars are then ‘walked’ in and out across the map to the desired location so that lines can be plotted to represent the direction to be travelled.

Kelvin Company History:

The origins of the company lie in the highly successful and strictly informal relationship between William Thomson (1824-1907), Professor of Natural Philosophy at Glasgow University from 1846-1899 and James White, a Glasgow optical maker. James White (1824-1884) founded the firm of James White, an optical instrument maker in Glasgow in 1850 and was involved in supplying and mending apparatus for Thomson university laboratory and working with him on experimental constructions. White was declared bankrupt in August 1861 and released several months later.

In 1870, White was largely responsible for equipping William Thomson laboratory in the new University premises at Gilmore hill. From 1876, he was producing accurate compasses for metal ships to Thomson design during this period and this became an important part of his business in the last years of his life. He was also involved in the production of sophisticated sounding machinery that Thomson had designed to address problems encountered laying cables at sea, helping to make possible the first transatlantic cable connection. At the same time, he continued to make a whole range of more conventional instruments such as telescopes, microscopes and surveying equipment. White's association with Thomson continued until he died.

After his death, his business continued under the same name, being administered by Matthew Edwards until 1891 when he left to set up his own company. Thomson who became Sir William Thomson and then Baron Kelvin of Largs in 1892, continued to maintain his interest in the business after James White's death in 1884, raising most of the capital needed to construct and equip new workshops in Cambridge Street, Glasgow. At these premises, the company continued to make the compass Thomson had designed during the 1870s and to supply it in some quantity, especially to the Admiralty. At the same time, the firm became increasingly involved in the design, production and sale of electrical apparatus.

In 1899, Lord Kelvin resigned from his University chair and became, in 1900, a director in the newly formed limited liability company Kelvin & James White Ltd which had acquired the business of James White. At the same time Kelvin's nephew, James Thomson Bottomley (1845-1926), joined the firm. In 1904, a London branch office was opened which by 1915 had become known as Kelvin, White & Hutton Ltd. Kelvin & James White Ltd underwent a further change of name in 1913, becoming Kelvin Bottomley & Baird Ltd.

Hughes Company History:

Henry Hughes & Sons were founded in 1838 in London as a maker of chronographic and scientific instruments. The firm was incorporated as “Henry Hughes & Sons Ltd” in 1903. In 1923, the company produced its first recording echo sounder and in 1935 a controlling interest in the company was acquired by S Smith & Son Ltd resulting in the development and production of marine and aircraft instruments.

Following the London office's destruction in the Blitz of 1941, a collaboration was entered into with Kelvin, Bottomley & Baird Ltd resulting in the establishing “Marine Instruments Ltd”. Following the formal amalgamation of Kelvin, Bottomley & Baird Ltd and Henry Hughes & Sons Ltd in 1947 to form Kelvin & Hughes Ltd. Marine Instruments Ltd then acted as regional agents in the UK for Kelvin & Hughes Ltd who were essentially now a part of Smith's Industries Ltd founded in 1944 and the successors of S Smith & Son Ltd.

Kelvin & Hughes Ltd went on to develop various marine radar and echo sounders supplying the Ministry of Transport, and later the Ministry of Defence. The firm was liquidated in 1966 but the name was continued as Kelvin Hughes, a division of the Smiths Group. In 2002, Kelvin Hughes continues to produce and develop marine instruments for commercial and military.

Significance

This model parallel map ruler is a good example of the commercial diversity of navigational instruments made by Kelvin & Hughes after World War II. It was made in numbers for use by shipping after the second world war and is not particularly rare or significant for it's type. Also it was made no earlier than 1947 as the firms of Kelvin, Bottomley & Baird Ltd and Henry Hughes & Sons Ltd who took over from Smith & Sons were not amalgamated until 1947. It can therefor be assumed that this ruler was made during the company's transitional period to Kelvin & Hughes from Smith Industries Ltd.

Physical description

Brass parallel rule in wooden box with blue felt lining.

Inscriptions & markings

Rule inscribed on front "Kelvin & Hughes Ltd" " Made in Great Britain"