Note 119 — Chapter XXXII · PERMIAN VOLCANOES OF ENGLAND
Reading edition
Allport, Quart. Journ. Geol. Soc. xxx. (1874), p. 547. Chemical analysis also shows the identity of the rocks and the nature of the alteration of the "white rock." See Jukes, "South Staffordshire Coal-field," pp. 117, 118.