The collection includes family correspondence, 1796 - 1841 and literary correspondence, 1810 - 1832. Amongst the writers are the poets, David Thomas, Dafydd Ddu Eryri; Roberts Davies, Gutyn Peris and Robert Davies, Bardd Nantglyn. Numerous correspondents thank Robert Thomas for his friendship and patronage and some letters have poems enclosed.
There is a volume of Welsh poetry, ca 1805 - 1836, containing works by the poets aforementioned and others such as Gwilym Caledfryn; Idris Mon; David Jones, Brydydd Hir. The volume also includes a poem by Anne Thomas, daughter of Robert Thomas.
Amongst the miscellaneous items there is Robert Thomas' will and a list of the tenants in Abercegin, Bangor, 1793 - 1828.