Seventeenth-century letters and papers, 1595-1699 and 1871 of the two branches of the Parsons family, the Parsonses of Bellamont, Co. Dublin, Viscounts Rosse, and the Parsonses of Parsonstown, alias Birr, King's County.
Eighteenth-century letters and papers, 1705-1887, of both branches of the Parsons family, but almost all of them deriving from the Parsonses of Parsonstown - excluding the papers of Sir Laurence Parsons, 5th Baronet, later 2nd Earle of Rosse, which constitute Sections C-F.
Correspondence of the 3rd and 4th Earls of Rosse with fellow-astronomers or about the Birr and other observatories, including correspondence of the 5th and 6th Earls about the Birr Observatory, 1840-1909, 1913-14, 1938 and 1964-84.
Legal agreements in the form of deeds and indentures relating to the Derenzy family’s title and interest in lands in the vicinity of Tinnycross, County Offaly. The earliest deed dating from 1630, records Sir Mathew de Renzi purchasing the townlands of Ballynashragh, Ballycosny, Tyrenehinan, Kilmore and Derry, all in the barony of Ballycowen, on behalf of his son Mathew DeRenzy, then at the bar in London. The vendor was Robert Branthwaite of London, who had been granted the land by letters patent of King James I. Further adjoining townlands of Rossnagouloge or Cappanure were purchased by Sir Mathew from Allen Jones in 1630, and the following year the adjacent townlands of Derrykilliagh and Kilbeg were purchased from Art McOwen O’Molloy. All were settled on his son, Mathew DeRenzy. The bulk of the collection consists of numerous leases and mortgages raised against the land by Mathew DeRenzy between 1699 and 1703, while he lived at Cloghbemon in County Wexford. Later items in the collection relate to the sale of the lands to Reverend James Cox, Archdeacon of Ferns.
Artificial collection of letters and papers, 1856-2006, received or assembled by other members of the Parsons/Rosse family, concerning the Hon. Sir Charles Parsons, the inventor of the turbine engine, a younger brother of the 4th Earl of Rosse.
Journals containing astronomical observations, drawings of nebula, drafts for articles and speeches on astronomy, and other papers (excluding correspondence) of the 3rd and 4th Earls of Rosse on the subject of astronomy, [pre-1828-1908].
Letters and papers, 1791-1841, of Sir Laurence Parsons, 2nd Earl of Rosse, including (during his lifetime) papers of his first and second sons, Lord Oxmantown and the Hon. John Clere Parsons, arranged by topic, and chronologically according to the date of the first item in each sub-section.
Letters and papers, 1765-c. 1820 and 1855, of Sir Laurence Parsons, 5th Baronet, who succeeded in 1807 as 2nd Earl of Rosse (of the second creation, the earldom in the elder branch of the Parsons family having died out in 1764), reflecting Parsons's youthful intimacy with Henry Flood, and consisting of correspondence and speech-notes of Flood, letters to Parsons from and about Flood, and drafts for biographical and historical writings by Parsons on Flood.