Born into an
Ulster-Scots family on 13 November 1786, Thomson was the fourth son of Agnes Nesbit and James Thomson, a small farmer, at Annaghmore, near
Ballynahinch,
County Down (the house was later called Spamount), in
Ulster. His early education was from his father. At age 11 or 12 he had found out for himself the art of
dialling. His father sent him to a school at
Ballykine, near Ballynahinch, kept by Samuel Edgar, father of
John Edgar. Thomson soon rose to be an assistant. Wishing to become a minister of the Presbyterian church, in 1810 he entered the University of Glasgow where he studied for several sessions, supporting himself by teaching in the Ballykine school during the summer. He graduated MA in 1812, and in 1814 he was appointed teacher of mathematics and arithmetic in the newly established
Academical Institution, Belfast; and in 1815 he was also appointed as professor of mathematics in its collegiate department. He was an able teacher and was an author of a number of very popular textbooks. In 1829 the honorary degree of LLD was conferred upon him by the
University of Glasgow, where in 1832 he was appointed sixth professor of mathematics. He held this post till his death on 12 January 1849. He is buried on the northern slopes of the
Glasgow Necropolis to the east of the main bridge entrance. The grave is notable because the modern memorial to
Lord Kelvin is at its side. ==Family==