Trails for Slate in Llanllechid Mountains, October 1818 It is stated in this book that it contains, An account of work done and money expended at Bryn Hafod y Wern common in the parish of Llanllechid in clearing rubbish and rock for the discovery of slates there – commencing on the 10th day of October 1818.The accounts include the amount of work carried out and for what rate between 10 October 1818- 20 March 1824. 10 October 1818- 20 March 1824