Slates from quarries in Wales once went to roof the world. By the late nineteenth century as many as a third of all the roofing slates produced worldwide came f
Cyfrol yn dangos ôl ymchwil trylwyr yn cyflwyno gwybodaeth am 60 o chwareli llechi Is-Gwyrfai, Rhyd-ddu, Beddgelert a Meol Tryfan, sir Gaernarfon, a weithredai