William Thomson was born in Belfast, the son of James Thomson, professor of mathematics at the University of Glasgow from 1832. Educated at Glasgow and Cambridge, he was appointed to the chair of Natural Philosophy (physics) at Glasgow at the unusually young age of twenty-two in 1846. From the outset of his career he exhibited that rare gift of being both a brilliant theoretical and applied physicist.
In the early 1850s he explained two of the laws of thermodynamics, but within a decade he was helping resolve the practical problems of laying the first Trans-Atlantic telegraph cable from Britain to the United States. Aware of the potential returns from such connections, he took care to patent his inventions. These he exploited through the firm of Jenkin, Varley & Thomson. Later he developed a link with the Glasgow instrument maker, James White, to exploit some of his inventions, particularly his famous Kelvin compass and his sounding machine.
An apostle of electric power, Thomson's house in the professorial quadrangle at Gilmorehill was the first in Glasgow to be lit with electricity. His knowledge of electricity was much in demand in the closing decades of his life. He became a rich man with a country house at Netherhall, near Largs, where he and his second wife entertained lavishly. He retired from his chair in 1899 at the age of seventy-five and was elected chancellor of the University. He was knighted in 1866 and made a peer in 1892, taking the title Lord Kelvin. Although a committed Free Churchman, he was buried in Westminster Abbey.