From A Compendium of Irish Biography, 1878
Darcy, Patrick, Count, an engineer officer, was born at Galway, 27th September 1723. He was sent to an uncle in Paris in 1739. There he studied under Clairaut, and at the age of seventeen distinguished himself by the solution of some extremely difficult mathematical problems. He made two campaigns in Germany and one in Flanders — being Colonel in the Irish Brigade at Rosbach in 1757. His essays on artillery and on scientific questions display genius and solidity of judgment. He died in Paris, of cholera, 18th October 1779, aged 56. A eulogium was pronounced upon him by Condorcet.
16. Authors, Dictionary of British and American: S. Austin Allibone. 3 vols. Philadelphia, 1859-'71.
42. Biographical Dictionary: Rev. Hugh J. Rose. 12 vols. London, 1850.
186. Irish Brigades in the Service of France: John C. O'Callaghan. Glasgow, 1870.