Dyddiadur y Methodistiaid Wesleyaidd ... 1891, containing entries, in Welsh, by Owen Thomas, ?Tre-garth, parish of Llandygái, co. Caernarfon, mainly comprising reflections on his spiritual condition, and including (p. 36) a reference to his fellow-workers ('fy nghyd-weithwyr') at the Penrhyn slate quarry.