Note 91 — Chapter X · THE CAMBRIAN VOLCANOES OF SOUTH WALES
Reading edition
See, for example, J. Davies, Quart. Journ. Geol. Soc. vol. xxiv. p. 164, xxxv. p. 203; also the paper already referred to, op. cit. xxxix. p. 315; and Mr. Teall's British Petrography, p. 334.