William Sebaw Cathcart, earl, a British general and diplomatist, born at Petersham, Sept. 17, 1755, died at Cartside, near Glasgow, June 17, 1843. He was the eldest son of the 9th Baron Cathcart, studied law, although without intention of practising that profession, and on the breaking out of the American war entered the British army, where he speedily rose to be aide-de-camp to Gen. Spencer Wilson and Sir Henry Clinton. Subsequently he commanded the 29th regiment of infantry, and finally was appointed quartermaster general. Recalled to England, he joined the Walcheren expedition with the rank of brigadier general. After distinguishing himself at Bommel and elsewhere on the retreat, he returned to England, where he was promoted. In 1807 he took his seat as a representative peer of Scotland. The same year he was appointed commander-in-chief of the troops destined to act against Copenhagen, and on the fall of that city and capture of the Danish fleet was created a peer of England as Viscount Cathcart and Baron Greenock. In 1812 he was sent as minister plenipotentiary to Russia. The emperor Alexander being then with the army, Lord Cathcart joined him at headquarters, where he remained during the campaigns of 1813 and 1814. He entered Paris with the allied sovereigns, subsequently acted as British plenipotentiary at the congress of Vienna, and was made an earl, June 18, 1814. On the final overthrow of Napoleon he again repaired to Paris and signed the treaty of peace which followed Waterloo, He was afterward for some time minister to Russia. His later years were passed at his country house of Cartside.