The Southern Chain--The Pentland Volcano--The Biggar Centre--The Duneaton Centre--The Ayrshire Volcanoes 317 CHAPTER XXI Volcanoes of the Lower Old Red Sandstone of the Cheviot Hills, Lorne, "Lake Orcadie" and Killarney 336 CHAPTER XXII Volcanoes of the Upper Old Red Sandstone--The South-West of Ireland, the North of Scotland 348 BOOK VI THE CARBONIFEROUS VOLCANOES CHAPTER XXIII The Carboniferous System of Britain and its Volcanic Records Geography and Scenery of the Carboniferous Period--Range of Volcanic Eruptions during that time--I. The Carboniferous Volcanoes of Scotland--Distribution, Arrangement and Local Characters of the Carboniferous System in Scotland--Sketch of the Work of previous Observers in this Subject 355 CHAPTER XXIV Carboniferous Volcanic Plateaux of Scotland I. The Plateau-type restricted to Scotland--i. Distribution in the Different Areas of Eruption--ii. Nature of the Materials Erupted 367 CHAPTER XXV Geological Structure of the Carboniferous Volcanic Plateaux of Scotland 1. Bedded Lavas and Tuffs; Upper Limits and Original Areas and Slopes of the Plateaux; 2. Vents; Necks of Agglomerate and Tuff; Necks of Massive Rock; Composite Necks; 3. Dykes and Sills; 4. Close of the Plateau-eruptions 383 CHAPTER XXVI The Carboniferous Puys of Scotland i. General Character and Distribution of the Puys; ii. Nature of the Materials Erupted--Lavas Ejected at the Surface--Intrusive Sheets--Necks and Dykes--Tuffs 414 CHAPTER XXVII Geological Structure of the Carboniferous Puys of Scotland 1. Vents: Relation of the Necks to the Rocks through which they rise--Evidence of the probable Subærial Character of some of the Cones or Puys of Tuff--Entombment of the Volcanic Cones and their Relation to the Superficial Ejections. 2. Bedded Tuffs and Lavas--Effects of Subsequent Dislocations. 3. Sills, Bosses, and Dykes 424 CHAPTER XXVIII Illustrative Examples of the Carboniferous Puys of Scotland The Basin of the Firth of Forth--North Ayrshire--Liddesdale 462 LIST OF ILLUSTRATIONS FIG. PAGE