About 30,000 letters, c. 1800 to c. 1900 relating to the Hill estates in Co. Down and elsewhere, mainly correspondence of the Marquis of Downshire with his chief agent and between the chief agent and agents of the individual estates, with particularly detailed correspondence for the period of the 3rd Marquis, 1813-45, dealing also with agriculture, linen trade, schools, roads, railways, canals, etc.