1784 - 1852
Thomas Colby was born in Rochester, England in September, 1784 to Welsh parents. From an early age he showed an affinity for mathematics and was schooled under the Rev W. Crakelt. From here he was transferred to the Royal Military Academy, Woolwich, and passed out for the Royal Engineers before his seventeenth birthday. In 1802 he was noticed by Major Mudge, of the Ordnance Survey, who asked that he should join them to follow the tradition that younger officers should be attached to the Survey to learn topographical drawing. Thus began Colby's association with the Ordnance Survey, which would last 45 years.
At this time the idea of mapping Great Britain was in its infancy, through the work of Mudge and Colby great progress was made. The young Lieutenant's first services appear to have been the measurement of an arc of meridian between Dunnose, Isle of Wight and a station near the mouth of the River Tees. Thomas Colby's career nearly came to an abrupt end in the year 1803. Practicing with a pistol, it exploded causing the amputation of his left hand and lodging a piece of the barrel in his skull. Fortunately Colby recovered enough to resume his duties although the piece of pistol lodged in his head would cause him pain throughout his life, and ultimately lead to his death.
In 1804 he was observing the Pole Star for azimuths at Beaumaris; in 1806 he was assisting Colonel Mudge in the measurement of a baseline on Rhuddlan Marsh near St. Asaph and in astronomical observations in Delamere Forest, Cheshire and on the Yorkshire moors. When he was not out measuring, he could be found in the ordnance map office in the tower of London, computing results and overseeing the construction and engraving of the Ordnance Survey maps. In 1819 it was reported that while exploring the eastern side of Inverness, Ross, and Caithness, and the mainland of Orkney, with a party of artillery men, Colby traversed on foot 1099 miles in 45 consecutive days, including Sunday's.
In the year 1820 Mudge had died, and the Duke of Wellington, then Master General of the Ordnance, consulted Sir Joseph Banks and other scientific authorities, and appointed Colby to succeed Mudge at the head of the Survey. In April 1820 Colby became a fellow of the Royal Society of London. In 1828 Colby married Elizabeth Boyd, and moved to Dublin to be within easy distance of the Irish survey offices. Under Colby's personal supervision the organisation of the Survey steadily developed, and the attempt to substitute speed for accuracy having finally been abandoned in 1832 lead to, in 1833, the publication of the first Irish county Ordnance Survey, Londonderry.
In 1846, just as the final sheets of the Irish Ordnance Survey were being completed, Colby attained the rank of Major-General, and in accordance with the rule of the service he was retired from the post he had held for so long. He died at New Brighton, near Liverpool on the 9th October, 1852 in his 69th year. Colby was a knight of Denmark, a member of the Royal Irish Academy, fellow of the Royal Societies of London and Edinburgh and a member of the institution of civil engineers.