Grubb, Thomas (1800–78), engineer and maker of telescopes and optical instruments, was born 4 August 1800 near Portlaw, Co. Waterford, into a quaker family, youngest child among two sons and one daughter of William Grubb (d. 1831), farmer, and Eleanor Grubb (née Fayle), his second wife; there were also three children from his father's first marriage. Probably self-educated, he was employed as a clerk in Dublin and may have worked in the Waterford shipyards or in a British machine-tool factory. About 1830 he established a foundry and engineering works near Charlemont Bridge, Dublin, which began by making metal billiard tables, but later earned an international reputation for the sound manufacture and original design of machine tools and high-precision optical and mechanical instruments, which included the construction of some of the world's finest telescopes.
As a hobby he built a small observatory equipped with a 9-in. (22.9 cm) reflecting telescope. His telescope came to the attention of Thomas Romney Robinson (qv), director of Armagh observatory, who befriended and promoted Grubb in his professional pursuits. Grubb's first big telescope commission (1834) was for the construction of an equatorial mounting for the 13.3-in. (33.8 cm) lens (by R. A. Cauchoix (1776–1845) of Paris) for Edward Joshua Cooper's (qv) observatory at Markree, Co. Sligo. This was at the time the world's largest aperture, and according to Robinson it was a ‘great leap forward’ (Glass, 13), representing a significant improvement in stability. In 1835 he produced for the Armagh observatory a 15-in. (38 cm) reflecting telescope, equatorially mounted, in which for the first time a triangular system of balanced levers shared the weight of the primary speculum – a system which, on Grubb's suggestion, was adopted by William Parsons (qv) (later 3rd earl of Rosse), for his 36-in. (91.5 cm) and later his 72-inch (183 cm) reflector, the ‘Leviathan of Parsonstown’ (Birr), in King's Co. (Offaly), the largest telescope in the world in 1845. Other major commissions included those for the Royal Greenwich Observatory, London (1838), and for the US military academy at West Point, New York (1840). In 1853 he exhibited a 12-in. (30.5 cm) refractor telescope at the Dublin Industrial Exhibition, which was later purchased for the Dunsink observatory, Dublin, fitted with a lens donated by Sir James South (1785–1867) and installed in a revolving dome designed by Grubb in 1868; overhauled in 1987, it remains in use. His last design and greatest achievement was the 48-in. (122 cm) equatorially mounted reflector for Melbourne, Australia; new workshops were built in Rathmines and his son Howard Grubb (qv) curtailed his engineering studies at TCD and entered the business in 1865 to aid his father. Completed in 1867, it was hailed as a masterpiece of engineering; however, the speculum mirror required sophisticated maintenance which was lacking in Melbourne, and it was eventually regarded as a relative failure. Grubb published privately The great Melbourne telescope (1870) in which he described its construction and replied to his critics.
Though Grubb was famous for his telescopes, only a minor part of his time was spent constructing them. An inventor of great originality, he was appointed to what became his main source of income, the post of engineer to the Bank of Ireland (c.1840–1878), where he designed and built ingenious machinery, which remained in use till 1921, for engraving, printing, and numbering banknotes; every banknote was identical, making the detection of forgeries much easier. In 1847 he devised for the government an early pantographic machine for engraving registration numbers on gun barrels. A pioneer in scientific lens design, he was probably the first to use the technique of ray-tracing, which is the standard technique for computer graphics, and contributed significantly to the development of microscopes; one of his microscopes is held in the Museum of the History of Science, Oxford, England. Other work undertaken included the supply of instruments for Humphrey Lloyd (qv), director of the Magnetic Observatory, TCD, for a network of forty magnetic observatories, which were built throughout the British colonies. An early practitioner of photography, he was a founding committee member (1854), secretary for many years and hon. treasurer (1857) of the Dublin Photographic Society (from 1858 The Photographic Society of Ireland), and lectured on photographic optics; he contributed articles to photographic journals and patented an improved camera lens (1858).
He published papers in a variety of learned journals (including the RIA Proceedings and the RDS Journal), recorded in I. S. Glass, Victorian telescope makers. He became a member of the British Association for the Advancement of Science (1835), and was elected MRIA (1839), FRS (1864), and fellow of the Royal Astronomical Society (1870). He retired c.1870, died 19 September 1878 at his home, 141 Leinster Road, Rathmines, Dublin, and was buried in Mount Jerome, Dublin.
When Tomas married Sarah Palmer on 12 September 1826, he was disowned by the Society of Friends as Sarah was not a quaker. Of their five sons and four daughters, three sons and two daughters died young. Their eldest son, Henry Thomas Grubb (1833–1902), studied engineering at TCD and succeeded his father as engineer to the Bank of Ireland, and his youngest son, Howard Grubb took over and expanded the family firm.