The Ancient Volcanoes of Great Britain, Volume 1 (of 2)Note 158 — Chapter XII · CHARACTERS OF THE SILURIAN SYSTEM IN BRITAIN. THE ARENIG VOLCANOESReading editionMr. Harker speaks of the rock as a granophyre.◇Copy noteReturn to CHAPTER XII CHARACTERS OF THE SILURIAN SYSTEM IN BRITAIN. THE ARENIG VOLCANOES