The series comprises diaries, 1836-1859, relating mainly to the Rev. John Jones's work as Unitarian minister of Hen Dŷ Cwrdd and as schoolmaster at Aberdare.

The series comprises diaries, 1858-1920, containing, in addition to personal news, information relating to the Rev. Rees Jenkin Jones's work as minister of Hen Dŷ Cwrdd, Aberdare, and schoolmaster of the Trecynon Seminary; editor of Yr Ymofynydd; and as student and teacher at Carmarthen Presbyterian College; together with an account of his visit to Egypt and Palestine, 1871. The extracts, 1836-1906, come from the diaries of Rees Jenkin Jones and from those of his father, the Rev. John Jones.

The series comprises notebooks and scrapbooks, covering [c. 1865]-1939, relating mainly to Unitarianism, in particular to the cause at Hen Dŷ Cwrdd, Aberdare, and at High Pavement Chapel, Nottingham.

The series consists of notes, [c. 1877]-1919, relating to the history of the Old Meeting House (Hen Dŷ Cwrdd), Aberdare; together with reports, 1908, from Unitarian churches relating to attendances; press cuttings, 1877, concerning the Llwynrhydowen eviction in 1876 and notes on ministers of Merthyr Tydfil and Cefncoedycymer.

The file comprises transcripts, 1758-1764, from the account book of the Rev. Solomon Harries, relating to a school which was opened by him in 1758 and listing the scholars. At the end there is a transcript in Welsh of a minute book of Hen Dŷ Cwrdd, Aberdare, 1858-1862, and press cuttings, 1923-1931, relating to the High Street Unitarian Church, Swansea.