Forster, Francis, (1831). ‘Geology of Ratcheugh Crag, near Alnwick ’, extract from Trans. Nat. Hist. Soc. Northumberland, Durham & Newcastle 1831. v1,
Forster, Francis, (1831). ‘Observations on the Geology of Ratcheugh Crag, near Alnwick [Northumberland]’, extract from Transactions of the Natural History Society of Northumberland, Durham and Newcastle upon Tyne, 1831. v1, pp 75-78 + foldout plate, a hand-coloured engraving ‘Section shewing the Effects of , 28 x43cm, 1:25,000 scale. Text and plate age-toned and clean. In good condition.