The Ancient Volcanoes of Great Britain, Volume 1 (of 2)Note 156 — Chapter XII · CHARACTERS OF THE SILURIAN SYSTEM IN BRITAIN. THE ARENIG VOLCANOESReading editionMem. Geol. Surv. vol. iii. p. 26.◇Copy noteReturn to CHAPTER XII CHARACTERS OF THE SILURIAN SYSTEM IN BRITAIN. THE ARENIG VOLCANOES