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 an account book, 1879-1893, containing payments made apparently by pupils attending Trecynon Seminary, Aberdare.