Watson received a commission as sub-engineer and lieutenant, after passing through Woolwich academy, on 17 March 1759. In 1761 he went in the expedition to Belleisle under Commodore Keppel and General Hodgson. He arrived on 7 April, and took part in the siege and capture of the place, which capitulated on 7 June. On 23 Feb. of the following year he was transferred to the 97th foot, James Forrester's regiment, and in March he went as sub-engineer with the expedition under Admiral Sir George Pocock and the Earl of Albemarle to Havana, arrived on 5 June, and took part in the siege with some distinction; the place capitulated on 14 Aug., and Watson was thanked by the commander of the forces, and afterwards by the king. On 4 Feb. 1763 he was promoted to a company in the 104th foot, and the same year he was recommended by Lord Clive to go to India.
He went to Calcutta in 1764, and on 1 May was appointed field-engineer with the rank of captain and commander of the troops in Bengal. He was sworn into the East India Company's service on 9 May. Lord Clive returned to India in May 1765, and appointed Watson chief engineer of Bengal, to which were added Behar and Orissa. Watson was employed upon the Fort William defences, and constructed works at Budge Budge and Melancholy Point. He was impressed with the necessity of dock accommodation at Calcutta, and obtained a grant of land upon which to build wet and dry docks, and lay out a marine yard for fitting out ships of war and merchantmen. The designs were approved, and the works were carried on for some years with vigour; but the board of directors stopped them for want of funds before they were finished.
Watson laid out a very large amount of his own money on them, but was unable to obtain any compensation, although he sent Mr. Creassey, the superintendent of the works, expressly to England to represent the case. He then constructed two ships, the Nonsuch, thirty-six guns, and Surprise, thirty-two. They were built by George Louch with native shipwrights under his personal direction, and were intended to prey upon the Spanish commerce off the Philippine Islands; but he shared the ill-favour into which his patron Clive had fallen: the application made by his agent for letters of marque was refused, and Watson employed the ships in commerce.
Watson was promoted to be lieutenant-colonel on 19 Jan. 1775, after his return to England. In 1776 he published a translation of Euler's 'Compleat Theory of the Construction and Properties of Vessels' (London, 8vo; 2nd edit. 1790). He enriched it with many additions of his own, and the English edition has this superiority over the French - that it contains a supplement which Euler sent the translator in manuscript just as he had finished the translation of the published French work. Watson applied the principles laid down in the construction of the vessels he built in India, which proved the fastest vessels then built.
In 1780 Watson was recalled to India, and took with him the mathematician Reuben Barrow, who had been assistant to Maskelyne at the royal observatory, and to whose care had been committed the celebrated Schiehallion experiments and observations.
Finding his health impaired by climate and hard service, Watson resigned the service on 16 Jan. 1786, and embarked in the spring; but his health failed, and he landed at Dover, only to die on 17 Sept. 1786. He was buried in a vault of St. Mary's Church, Dover, on the 22nd. An engraved portrait is mentioned by Evans (Cat. i. 11006).
Watson married in India, and his wife accompanied him to England. Having omitted to alter a will made before marriage, his considerable fortune went to a natural daughter living under the care of Mrs. Richardson of Holbeach. She married Charles Schreiber.
[India Office Records; War Office Records; Royal Engineers' Records; European Magazine, 1787, which contains a portrait of Watson; Gent. Mag. 1786, 1810, and 1833; Notes and Queries, 1st ser. i. and iii.]
WATSON, HEWETT COTTRELL (1804–1881), botanist, was born on 9 May 1804 at Park Hill, Firbeck, Yorkshire. His father, Holland Watson, was nephew of John Watson (1725-1783) [q. v.] His mother, Harriett, daughter of Richard Powell of Heaton-Norris, near Stockport, was descended from the last Lord Folliott of Ballyshannon. In 1810 the family removed to Congleton, Cheshire, and young Watson was sent first to Congleton grammar school, where he had the reputation of a dunce, and was then placed under the Rev. J. Bell at Alderley. Dr. Stanley (afterwards bishop of Norwich) was then rector of Alderley, and first encouraged a love of botany in the boy, while Watson often protected the frail, delicate Arthur Stanley (afterwards dean of Westminster), who was one of his schoolfellows though eleven years his junior. A permanent injury to the joint of one of his knees