Comprises 23 letters written by Frederick Jennings Thomas during his naval service between 1799 and 1811, to his father Sir John Thomas, his mother Lady Thomas and his sister Miss Mary Thomas.

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Administrative / biographical background
Thomas was born on 19 April 1786, the younger son of Sir John Thomas, fifth baronet (1749–1828), of Wenvoe Castle, Glamorgan, and his wife, Mary, daughter of John Parker of Hasfield Court, Gloucestershire. He entered the navy in March 1799 on the BOSTON on the North American station, and afterwards in the West Indies. In autumn 1803 he joined the PRINCE OF WALES, flagship of Sir Robert Calder, and was present in the action off Cape Finisterre on 22 July 1805. On 19 September he was appointed acting lieutenant of the SPARTIATE (commission confirmed 14 February 1806) and was at Trafalgar. He continued in the SPARTIATE off Rochefort, and afterwards in the Mediterranean until November 1809, when he was for a few months on the ANTELOPE, flagship of Sir John Duckworth, and was then sent to Cadiz, where for the next three years he helped to defend the town against the French flotilla. He was promoted commander on 4 March 1811, and second in command of the British flotilla. Towards the close of 1813 he was acting captain of the SAN JUAN (74 guns), flagship of Rear-Admiral Samuel Hood Linzee at Gibraltar. He was posted captain on 8 December 1813 and returned to England with Linzee in the frigate EUROTAS in 1814. He had no further employment afloat. On 7 August 1816 he married Susannah, only daughter of Arthur Atherley of Southampton and they had three sons and a daughter. In 1818 Thomas invented a lifeboat with three keels, intended to prevent it capsizing, and he proposed a pier at Brighton and a bridge across the River Arun in Sussex. He published England's Defence. He accepted the retired rank of rear-admiral on 1 October 1846 and died at Hill, near Southampton, on 19 December 1855. He was buried at Millbrook, near Southampton. Frederick Jennings Thomas's service record is at The National Archives, see: ADM 196/6/392. For his career history see Marshall's Naval Memoirs, 1823.