Ussher, Henry (1741–90), astronomer, was fourth son of the Rev. Samuel Ussher (1695–1771), rector of Dunganstown, Co. Wicklow, and Frances Ussher (née Walsh). His grandfather, John Ussher of Mount Ussher, Co. Wicklow, was a master in chancery and third son of William Ussher of Portrane, Co. Dublin. The family was of Anglo-Norman ancestry; an earlier relation was Arland Ussher, mayor of Dublin (1469). Little is known of his early schooling but it is assumed he was privately educated. In 1759 he entered TCD on a scholarship and graduated BA (1761) and MA (1764). He was elected fellow in 1779 and received BD and DD that same year. In 1781 he was elected senior fellow, prior to his appointment (1783) as TCD's first professor of astronomy, a position made possible by an endowment of Francis Andrews (qv), provost of TCD. At this time other universities had well established schools of astronomy and it became desirable that this subject should be available to scholars in Trinity. In his will Andrews left a sum for the development of an astronomical observatory for the college and for supporting staff, including a professorship. Ussher was chosen because he supported politically the provost of the time, John Hely-Hutchinson (qv), but he was not an astronomer as such. However, he had a strong interest in meteorological phenomena and had a small telescope at his home in Dublin. In order to gain experience in astronomy, he spent time at Greenwich observatory with the astronomer royal, Nevil Maskelyne. Over the next few years (1785–91) both men contributed to the planning of the first Irish observatory.
As professor, Ussher was responsible for choosing the site, planning the observatory, and supervising its construction. A number of elevated sites were considered: Howth Head, the open heaths of Foxrock, and the hill at Killiney. However, in the days before railways, Dunsink was chosen as the most suitable site within a reasonable four-mile walk of TCD. The uninterrupted horizon and the local climate was also deemed more suitable, with less occurrence of mist, haze, and fog. Within three years of Ussher's appointment the observatory was built and equipped with instruments by Jesse Ramsden (London) and clocks by John Arnold (London) and John Crosthwaite (Dublin). Some of these were in working order after more than 200 years.
In 1785 the Royal Irish Academy came into being, and Ussher, as a founding member, read to the Academy an ‘Account of the observatory belonging to Trinity College’, on 13 June 1785, around the time the building was near completion. The drawings and description of the observatory became the first memoir published in the Academy's Transactions (1787), although the plans were more extensive than the final building. His imaginative and thoughtful design took fully into account the needs of the instruments of the day. The meridian room was considered his masterpiece.
His seven other publications are also found in the Transactions and, although not extensive, are a record of the first systematic astronomical observations in Dublin. In 1787 Ussher installed a Ramsden transit telescope and began regular observations of the sky. The following year Francis Beaufort (qv), aged 14, was sent by his father Daniel Beaufort (qv), a friend of Henry Ussher, to study at the observatory for five months. Beaufort later became hydrographer of the Royal Navy, and his only formal scientific training occurred at Dunsink. It is said that Ussher's encouragement and guidance of Beaufort was one of his greatest achievements (Wayman, 18).
Ussher married Mary Burne; they had three sons and five daughters. His son Thomas Ussher (d.1848) served in the Royal Navy. Ussher died suddenly of ‘a putrid fever’ (Universal Magazine, 1790) on 8 May 1790 at his home in Harcourt St. and was buried in TCD chapel. His wife appealed to the college for a pension on the grounds that his ill-health and early death had been caused by his nightly observatory vigils. A pension was granted, as were monies for the printing of his astronomical papers. There was also a promise to publish his sermons and produce a bust for the observatory as well as a prize for an essay entitled ‘The death of Ussher’. However there is no evidence of any publications, bust, or prize.
After his death (1791) the holder of the chair of astronomy became Andrews professor of astronomy and astronomer royal of Ireland. Unfortunately, despite his groundbreaking work, Ussher never had the satisfaction of either title during his life. The year he died, his transit book (1788), containing all his professional observations at Dunsink, was taken to Armagh observatory by James Archibald Hamilton (qv), unknown to Ussher's successor John Brinkley (qv). Thirty-seven years later Brinkley was made aware of its existence.