The following is the entry for George Oldmixon in William O'Byrnes 1849 'Naval Biographical Dictionary'.
OLDMIXON. (Commander, 1847. f-p., 13; h-p., 26.)George Oldmixon is son of the late Sir John Oldmixon, and brother of Lieuts. John William and William Henry Oldmixon, R.N. A third brother, Edward, having fought and bled on the Canadian lakes without reward, entered the service of the United States.
This officer entered the Navy, 23 June, 1808, as Fst.-cl. Vol., on board the Bellona 74, Capt. John Erskine Douglas, with whom he continued to serve, as Midshipman and Master’s Mate, in the same ship and in the Prince of Wales 98, on the Halifax, Home, and Mediterranean stations, until July, 1814. In the Bellona he witnessed Lord Cochrane’s destruction of the French shipping in Basque Roads, and was present at the siege of Flushing in 1809; and, when in the Prince of Wales, he served on shore at the reduction of Genoa in April, 1814. After cruizing six months in the Channel on board the Hope 10, Capt. Henry Fyge Jauncey, he sailed for Jamaica as a Supernumerary in the Warrior 74, bearing the flag of his former Captain, then Rear-Admiral Douglas. He was promoted, on his arrival, to a Lieutenancy, 1 June, 1815, in the Tanais 38, Capt. Joseph James, in which frigate he remained until June, 1816; and he was subsequently appointed – 10 Nov. 1842, to the command of the Megaera steamer, which vessel he unfortunately lost off Port Royal, Jamaica, in March, 1843 – 12 Jan. 1844, as Senior, to the Hecate steam-sloop, Capts. Jas. Paterson Bower and Joseph West, employed at first on particular service, and next on the coast of Africa – and 11 June, 1846, to the acting command of the Flying Fish sloop, on the station last mentioned. He was advanced to his present rank soon after his return to England, 27 Sept. 1847.
Commander Oldmixon is married to a sister of Sir Wm. Scott, Bart., of Ancrum, Roxburghshire. Agents – Messrs. Chard.