Thomas Octavius Callender

Sir Thomas Octavius Callender (born 9 April 1855 at Clydeview, Partick, Lanarkshire, Scotland; died on 2 December 1938 at Bidborough Court near Tunbridge Wells, Kent) was an engineer and businessman, who promoted the electrical industry.

Thomas Callender was the eldest of the ten children of William Ormiston Callender of Bournemouth (1827–1908), a commission merchant, and his wife, Jean, née Marshall, the daughter of a Greenock tanner. He went to school at Greenock, in London and later at Boulogne-sur-Mer. During the Franco-Prussian War, he had to leave France and later he joined his father's company in London, where he focussed on the asphalt, paving, and bitumen refining business, which his father had set-up. Thomas Callender and his brother founded, in 1877, together with their father, who had acquired an interest in part in the import of bitumen from Trinidad for road-making and other waterproofing purposes - Pitch Lake. The offices were located at 150 Leadenhall Street, London, with a small refinery at Millwall, where the bitumen was landed. Large amounts of bitumen were refined and used for road-making and building purposes. Callender ensured that all impurities be removed at source, to reduce transporting costs. The company obtained many overseas road-making contracts.

On a visit to St Petersburg in 1880, Callender was impressed by opera house being lit by Yablochkov candles. To exploit the developing market for electric lighting, Callender decided to change the business towards the production of high-current insulated cables.

1881 tests on the production of insulated wire with patented vulcanized bitumen began at their new factory at Erith, Kent. 1882 Callender's Bitumen Telegraph and Waterproof Company was formed to finance the development of vulcanized bitumen. In the early 1880s, Callender invented the Callender solid system, where cables were laid in wooden troughs and embedded in bitumen.

Callender was responsible for the management of the Erith works. These supplied cables for the electric lighting of the new law courts in the Strand of London and for the Covent Garden Opera House in 1883, as well as mains cables for the growing number of electricity supply companies.

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