The Ancient Volcanoes of Great Britain, Volume 1 (of 2)Note 143 — Chapter XII · CHARACTERS OF THE SILURIAN SYSTEM IN BRITAIN. THE ARENIG VOLCANOESReading editionMem. Geol. Survey, vol. iii. 2nd edit. pp. 249, 250.◇Copy noteReturn to CHAPTER XII CHARACTERS OF THE SILURIAN SYSTEM IN BRITAIN. THE ARENIG VOLCANOES