Papers from the library of O. J. Hughes, estate agent, Nantlle, including versions of a report, 1888, on the Llwyngwern Slate and Slab Quarry, Corris, Merioneth, together with monthly particulars of production, profit or loss, etc., 1886-8; a report on Daren y Gessel Slate and Slab Quarry, Pennal, Merioneth, signed by O. J. Hughes; and an incomplete essay (19 pp.) entitled 'Traethawd ar lechfaeni Nant Nantllef', 1868.

Ledger and journal of Gaewern Slate works, Machynlleth, 1835-1856; accounts and notebooks of the Ratgoed and Cymerau Slate Quarries, Tal-y-llyn, and Llwyngwern Slate Quarry, Llanuwchllyn, 1853-1899; ledgers and notebook of the Cambrian Slate Works, Machynlleth, 1899-1909; minute books of the Abercorris Slate Quarry Company, Rhiwgwreiddyn, Corris, 1893-1909, and the Towyn Company, Tywyn, 1893-1903; and miscellaneous accounts and ledgers, 1827-1909.