son of Matthew Pepper Manby of Hilgay in Norfolk, lieutenant of marines, captain in the Welsh fusiliers, and afterwards aide-de-camp to Lord Townshend when lord-lieutenant of Ireland (1767–72). George William Manby [q. v.] was his elder brother. When lieutenant-general of the ordnance, Townshend gave his aide-de-camp's son, Thomas, a post in the department, but the boy, preferring to go to sea, was entered on board the Hyæna frigate on the Irish station, in 1783. In 1785 he was moved into the Cygnet sloop, in which he went to the West Indies. He was afterwards in the Amphion, and, returning in her to England, served for a short time in the Illustrious. Towards the end of 1790 he joined the Discovery, then fitting out for a voyage to the Pacific and the north-west coast of America, under the command of Captain George Vancouver [q. v.] In the beginning of 1793, when it was necessary to send some of the officers of the expedition to England and to China [see Broughton, William Robert; Mudge, Zachary], Manby was appointed master of the Chatham brig, the Discovery's consort, in which he remained for the next two years, engaged in the arduous and trying work of the survey. In 1795 he was moved back into the Discovery as acting lieutenant, and on his arrival in England was confirmed to that rank, 27 Oct. 1795. In 1796 he was a lieutenant of the Juste, and when Lord Hugh Seymour [q. v.] was preparing for an expedition to the Pacific, Manby, at his request, was promoted, 5 Feb. 1797, to command the Charon, a 44-gun ship, but armed en flûte, as a store-ship. The proposed expedition was afterwards countermanded, and the Charon was employed in transporting troops to Ireland during the rebellion. It is mentioned that on one occasion she took on board a thousand men at Portsmouth, landed them at Guernsey within twenty-four hours, embarked another thousand in their stead, and landed these on the following day at Waterford. She was also frequently engaged in convoying the local trade, and in cruising against the enemy's privateers. In the two years during which Manby commanded her he is said to have given 'protection to no less than 4,753 vessels, not one of which was lost.'
He was advanced to post rank 22 Jan. 1799, and towards the end of the year was appointed to the Bordelais, a remarkably fine and fast vessel, which had been built as a French privateer, but had fortunately been captured on her second trip by the Révolutionnaire, herself a prize, the work of the same builder. She was thought a most beautiful model, though dangerous from the weakness of her frame. During 1800 she was cruising for some time off the Azores, and was afterwards employed on the blockade of Flushing. She proved, however, very unfit for this service. She was long, narrow, and low in the water, and consequently so wet that her crew became very sickly. She was therefore ordered to Spithead, and thence to the West Indies. She sailed at the end of the year with the Andromache frigate and a large convoy. The convoy was dispersed in a gale off Cape Finisterre, and Manby was afterwards sent to look out for the stragglers to the eastward of Barbados. On his way he recaptured two of them, already prizes to a French privateer, and on 28 Jan. 1801 fell in with two large brigs and a schooner, French ships of war, which had been sent thither by the governor of Cayenne to prey on the English West Indian fleet. The armament of the brigs was very inferior to that of the Bordelais, but they carried nearly twice the number of men, and apparently thought to carry her by boarding. No sooner, however, did the Bordelais open her fire on the leading brig, the Curieuse, than the others turned and fled. After a gallant fight the Curieuse struck her flag, but she was in a sinking condition, and sank shortly after (James, iii. 124; Troude, iii. 249). The little affair derived importance from the fact of its saving the scattered convoy from a very great danger. During the year Manby was employed in active cruising, and on the peace he was moved into the Juno, one of the squadron on the coast of St. Domingo, and in her he returned to England in August 1802.
He was shortly afterwards appointed to the Africaine, a frigate mounting 48 guns, in which on the renewal of the war he was stationed off Helvoetsluys, with a 24-gun frigate in company, to blockade two large French frigates lying there with troops on board. This irksome service lasted for nearly two years, when, the French frigates having been dismantled, and having passed through the canal to Flushing, the Africaine joined the squadron off the Texel. After sustaining serious damage in a heavy gale, she was compelled to go to Sheerness to refit. Thence she was sent to the West Indies with convoy. She arrived at Barbados with a crew of 340 men, in perfect health. She was ordered to return to England with the homeward-bound trade, and to take on board some invalids from the hospitals. Within forty-eight hours after her departure from Carlisle Bay virulent yellow fever was raging on board. The surgeon and the
