Note 184 — Chapter XIII · THE ERUPTIONS OF LLANDEILO AND BALA AGE
Reading edition
See Silurian System, p. 401; Sheet 40 of the Geological Survey Map; Memoir of A. C. Ramsay, p. 232 et seq.; De la Beche, Trans. Geol. Soc. 2nd series, vol. ii. part i. (1826), p. 3.