Account book, 1846-1856, of Rowland Thomas ('Idris Ddu', 1789-1856) of Merthyr Tudful, co. Glamorgan, containing records of payments to members of the Solid Rock of Wales Society ('Cymdeithas Cadarn Graig y Cymry') meeting at the Harp, Penllwynderi, Merthyr, together with other miscellaneous accounts and memoranda, including an account of William Howel's journey with Abel Evans (d. 1866) and the Mormons from Merthyr to St Louis, Missouri, 1849 (ff. 79-81); additions, 1859-1868, in the hand of Rowland Thomas's son, William R. Thomas, include verses in Welsh (ff. 26v, 119v), and brief details of literary competitions at the National Eisteddfod, Rhuthun, 1868 (ff. 118v-19).