Hamilton, William (1755–97), cleric and geologist, was born 16 December 1755 in Derry city, son of John Hamilton, merchant, and Elizabeth Hamilton (née Hope). He entered Trinity College Dublin (TCD) in 1771 and had a distinguished academic career. He graduated Bachelor of Arts in 1776, Master of Arts in 1779, Bachelor of Divinity in 1787 and finally Doctor of Divinity in 1794. He was elected to fellowship in 1779, and founded the Palaeosophers, which amalgamated with the Neosophers to form the nucleus of the Royal Irish Academy (RIA) in 1785; he also founded the Dublin University Museum (1777), which soon acquired fine mineralogical and geological collections. He resigned his fellowship 27 January 1790 and took up the college living of Clondevaddock, Co. Donegal, a large parish between Mulroy Bay and Lough Swilly, where he ministered and acted as a local magistrate.
Hamilton wrote an important memoir on the Antrim coast, Letters concerning the northern coast of the county of Antrim (1786; German ed. 1787), which did much to advance the volcanic theory for the origin of basalt at a time when this was questioned by many in Europe. The 1822 edition included a memoir and portrait of its author. In the Transactions of the Royal Irish Academy he examined experimental methods for determining the earth's surface temperature (1788), and wrote on Ireland's climate (1794), a subject on which he later produced an important memoir (1797).
He also wrote an attack on democracy and French revolutionary principles and their danger for Britain and Ireland (1793). In 1796–7 he was a particularly active magistrate, often leading military detachments in vigorous searches for arms through north Donegal and Londonderry. He became the focus of much ill feeling; his rectory was attacked in February 1797 and he had to employ bodyguards. In March 1797 he was murdered by a group of suspected united Ireland supporters that targeted him in an attack on the house of Reverend John Waller at Sharon, Co. Donegal. He is buried in the grounds of Derry cathedral, and is commemorated by a plaque in the cathedral. His murder spurred Dublin Castle into introducing martial law and ordering the brutal disarming of Ulster under General Gerald Lake, which began in March 1797 within days of Hamilton’s death.
He married (13 May 1780) Sarah Walker; they had thirteen children, of whom eight or possibly nine survived him. They and his widow were provided for after his death by a grant from the House of Commons. Some of his papers are in the National Archives of Ireland.