# Dictionary of National Biography, 1885-1900/Roy, William (1726-1790)

​ROY, WILLIAM (1726–1790), major-general royal engineers, son of John Roy (1697–1748), was born at Milton Head in Carluke parish, Lanarkshire, on 4 May 1726. He was baptised on 12 May, when Captain Walter Lockhart of Lee was a witness. His father and grandfather were both factors to the Gordons of Hallcraig. The father was ordained an elder of the kirk on 3 July 1737, and died in 1748. William Roy and his brother James (b. 1730) were educated first at Carluke parish school, and afterwards at Lanark grammar school. James became a minister, and died at Prestonpans, Haddingtonshire, on 3 Sept. 1767, aged 37.
In 1746 William Roy was appointed an assistant to Lieutenant-colonel David Watson, who, as deputy quartermaster-general to the forces, was employed under the immediate orders of the Duke of Cumberland to carry out an extension of Marshal Wade's plan for the subjection of the clans by opening up communication through the Scottish highlands. Roy was occupied in 1747 in the construction of an encampment near Fort Augustus, and in superintending road-making by the troops. He aided Watson in preparing the map known as the Duke of Cumberland's map of the mainland of Scotland; but it would be more accurately described as a magnificent military sketch than as a cadastral survey. It was never engraved, and is now in the British Museum, in thirty-eight divisions, contained in eight cases, with ​a small index map attached. Its revision and completion were contemplated in 1755, but prevented by the outbreak of war. At a later date the map was reduced by Watson and Roy, engraved in a single sheet by T. Chievos, and published as the king's map. Roy's love of archæology showed itself in the insertion of the names of Roman places and camps.
On 23 Dec. 1755 Roy, who had already received a commission in the 4th King's Own foot, was made a practitioner-engineer. A serious alarm of a French invasion caused the removal from Scotland of Watson and his two assistants—Roy and David Dundas (1735–1820) [q. v.]; the latter joined Roy in Scotland in 1752. They were now employed in making military reconnaissances of those parts of the country most exposed to attack. Roy's share mainly consisted of the coasts of Kent and Sussex. He was, however, so neat a draughtsman—as numerous drawings in the British Museum testify—that besides his own surveys, he frequently drew the maps of country surveyed by Watson and others. In 1757 Roy took part in the expedition against Rochefort under Sir John Mordaunt (1697–1780) [q. v.], and was present at the capture and demolition of the fortifications of the Isle d'Aix. He gave evidence before the general court-martial at the trial of Mordaunt.
On 17 March 1759 Roy was promoted to be sub-engineer and lieutenant, and on 10 Sept. the same year to be engineer and captain in the corps of engineers. Roy served under Lord George Sackville in Germany this year, and took part in the battle of Minden, 1 Aug. On 20 Aug. he was promoted in the infantry from captain-lieutenant of Brudenell's, or 4th foot, to be captain of a company in the corps of highlanders. In 1760 Roy gave evidence before the general court-martial at the trial of Lord George Sackville. During 1760 and 1761 Roy served in Germany as deputy quartermaster-general of the British force under the Marquis of Granby, and took part in all the operations in which that force was engaged. On 11 Nov. 1761 he was promoted major of foot, and appointed deputy quartermaster-general of the forces in South Britain. On 23 July 1762 he was promoted lieutenant-colonel in the army, returning to Germany to serve again under the Marquis of Granby as deputy quartermaster-general.
On the conclusion of peace in 1763 Roy was entrusted with a general survey of the whole island of Great Britain; but the scheme came to nothing. Roy went to Scotland in 1764, and collected material for his work on military antiquities.
On 19 July 1765 Roy was appointed by royal warrant to a new post, entitled surveyor-general of the coasts and engineer for making and directing military surveys in Great Britain. His new duties were in addition to those of deputy quartermaster-general to the forces and engineer-in-ordinary. In October he was sent to Dunkirk on special service, with an allowance of 3l. a day, to examine into the state of the demolitions which were being carried out under the treaties with France. Roy met at Dunkirk his colleagues, Colonels Desmaretz and Andrew Fraser. Their report upon the Mardyke channels, dated 15 Feb. 1766, and the plans of Dunkirk made by Fraser, are in the royal artillery library at Woolwich.
In 1766 Roy visited Ireland, and wrote ‘A General Description of the South Part of Ireland, or Observations during a Short Tour in Ireland,’ 1766. The work was not printed; the original manuscript is in the British Museum. In 1767 he became a fellow of the Royal Society of London, and he was also a fellow of the Society of Antiquaries.
In 1768 he seems to have visited Gibraltar, and next year he submitted to the master-general of the ordnance a report upon the defences of this fortress, with projects for their improvement. In September 1775 Roy visited Jersey and Guernsey to report on housing additional troops. On 29 Aug. 1777 he was promoted to be colonel in the army, and on 19 Oct. 1781 to be major-general. In 1782 Roy was examined by the public accounts commission on his experience in regard to expenditure in the last war in Germany when he was in charge of both the quartermaster-general's and the chief engineer's departments. On 1 Jan. 1783 Roy was appointed director and lieutenant-colonel of royal engineers, and shortly after was made a member of a committee on the defences of Chatham. On 16 Sept. Roy was promoted colonel in the royal engineers, and was appointed a member of the board on fortifications presided over by the Duke of Richmond. On 15 Nov. 1786 Roy became colonel of the 30th regiment of foot.
Roy occupied his leisure time in scientific and archæological pursuits. In 1778 he read a paper before the Royal Society, entitled ‘Experiments and Observations made in Britain in order to obtain a Rule for measuring Heights with the Barometer.’ It was published separately the same year. In 1783 Roy was employed by the English government to carry a series of triangles from London to Dover, and connect them with the triangulation already made between Paris ​and the north coast of France, in order to determine the relative positions of the observatories of Paris and Greenwich. The scheme was suggested by the French government. Roy selected Hounslow Heath for a base line, which was measured in the summer of 1784 three times over by means of cased glass tubing, seasoned deal rods, and a coffered steel chain made by Ramsden, the length being 27,404 feet, and the discrepancy between the several measurements under three inches. This work took nearly three months, and excited considerable scientific interest, the king, the master-general of the ordnance, and many distinguished savants visiting Hounslow during its progress. The result of a remeasurement of the base on Hounslow Heath in 1791 by Captain Williams, Mudge, and Dalby was only 23/4 inches different from Roy's measurement, and the mean of the two was accepted as the true measurement.
In 1785 Roy contributed a paper to the ‘Transactions’ of the Royal Society on the measurement of this base, which was separately published the same year in a quarto volume. On 30 Nov. he was presented with the Copley medal of the Royal Society for the skill with which he had conducted the measurement of the base line on Hounslow Heath, accompanied by a highly complimentary speech from the president. He also wrote a paper for the Royal Society, entitled ‘An Account of the Mode professed to be followed in determining the Relative Situations of the Royal Observatories of Greenwich and Paris.’ This was read in 1787, and published separately in the same year in a quarto volume.
In the summer of 1787 Roy carried his triangulation from the Hounslow base to the Kentish coast, and on 23 Sept. met the French commissioners at Dover, and, after a conference with them, the observations connecting the English with the French triangulations were made from both sides of the Channel. A base of verification, 28,535 feet long, was measured on Romney Marsh under Roy's direction, and found to differ only twenty-eight inches from its calculated length as determined by the triangulations of the Hounslow base. Roy continued in 1788 and the following year the observation of a great number of secondary triangles, which became the foundation of the topographical survey of Middlesex, Surrey, Sussex, and Kent. He wrote for the Royal Society ‘An Account of the Trigonometrical Operations by which the Distance between the Meridians of the Royal Observatories of Greenwich and Paris has been determined;’ but Roy's health had failed, and he was able to give it only the leisure which illness and his military avocations permitted. In November 1789 he was obliged to go to Lisbon for the winter, returning to England in April 1790. He died suddenly at his house in Argyll Street, London, while correcting the proof-sheets of the above-mentioned paper, on 1 July 1790.
Roy left ready for the printer his ‘Military Antiquities of the Romans in Britain, and particularly their Ancient System of Castrametation illustrated from Vestiges of the Camps of Agricola existing there.’ His executors presented the manuscript to the Society of Antiquaries, who published it at the expense of the society, in a handsome folio volume, in 1793.
In addition to the works enumerated above, there are in the British Museum the following maps and plans drawn by Roy between 1752 and 1766: Roman Post at Ardoch; Culloden House; Roman Camp, Dalginross, Glenearn; Esk River; Kent, New Romney to North Foreland; Louisbourg; Milford Haven; Roman Temple at Netherby, Cumberland; Strathgeth Roman Post, near Innerpeffrey, Strathearn; Coast of Sussex; South-east part of England; Country between Guildford and Canterbury; Hindhead to Cocking; Lewes Road from Croydon to Chailey; Country from Dorchester to Salisbury; Country from Gloucester to Pembroke; Marden Castle, near Dorchester.
In Sir Walter Scott's ‘Antiquary’ Jonathan Oldbuck of Monkbarns relates his discovery of the site of the final conflict between Agricola and the Caledonians, and reflects on Roy for having permitted the spot to escape his industry.
R. H. V.