Casgliadau Arlein
Amgueddfa Cymru
Chwilio Uwch
The Penrhyn Quarry (booklet)
18 page booklet with diagrams and b/w photographs. Describes the geology, history, uses of slate etc.
Nid yw sylwadau ar gael ar hyn o bryd. Ymddiheuriadau am yr anghyfleustra.