Sir Thomas Livingstone Mitchell, a British engineer, born in Stirlingshire, Scotland, in 1792, died near Sydney, Australia, Oct. 5,1855. He joined the British army in the peninsula in 1808, attained the rank of major, and made military maps of the peninsular battle fields. In 1827 he was appointed deputy surveyor general of eastern Australia, and ultimately surveyor general which office he held till his death. He conducted four expeditions into the interior of Australia; the first, in 1831-'2, resulted in the discovery of the Peel and Nammoy rivers; and during the second and third, in 1835-6, the Darling and Glenelg rivers were explored, and Australia Felix discovered. The fourth (1845-'6) was undertaken to trace out a route from Sydney to the gulf of Carpentaria; the loss of cattle and horses prevented the completion of the expedition, but it led to the discovery of the Victoria river. During a visit to England Major Mitchell published "Three Expeditions into the Interior of Eastern Australia, with Descriptions of the recently explored Region of Australia Felix," etc. (2 vols. 8vo, London, 1838); and his " Journal of an Expedition into the Interior of Tropical Australia " appeared in 1848. In 1853 he published a lecture on the boomerang propeller, which he had invented for steam vessels.

He was knighted in 1839, and made a colonel in 1854.