CONTENTS

BOOK I GENERAL PRINCIPLES AND METHODS OF INVESTIGATION CHAPTER I

PAGE

Earliest Knowledge of Volcanoes—Their Influence on Mythology and Superstition—Part taken by Volcanic Rocks in Scenery—Progress of the Denudation of Volcanoes—Value of the Records of former Volcanoes as illustrating Modern Volcanic Action—Favourable Position of Britain for the Study of this Subject 1

CHAPTER II

The Nature and Causes of Volcanic Action—Modern Volcanoes 10

CHAPTER III

Ancient Volcanoes: Proofs of their existence derived from the Nature of the Rocks erupted from the Earth's Interior. A. Materials erupted at the Surface—Extrusive Series. i. Lavas, their General Characters. Volcanic Cycles. ii. Agglomerates, Breccias and Tuffs 14

CHAPTER IV

Materials erupted at the Surface—Extrusive Series—continued. iii. Types of old Volcanoes—1. The Vesuvian Type; 2. The Plateau or Fissure Type; 3. The Puy Type. iv. Determination of the relative Geological Dates of Ancient Volcanoes. v. How the Physical Geography associated with Ancient Volcanoes is ascertained 39

CHAPTER V

Underground Phases of Volcanic Action. B. Materials injected or consolidated beneath the Surface—Intrusive Series: I. Vents of Eruption—i. Necks of Fragmentary Materials; ii. Necks of Lava-form Materials; iii. Distribution of Vents in relation to Geological Structure-Lines; iv. Metamorphism in and around Volcanic Cones, Solfataric Action; v. Inward Dip of Rocks towards Necks; vi. Influence of contemporaneous Denudation upon Volcanic Cones; vii. Stages in the History of old Volcanic Vents 52

CHAPTER VI

Underground Phases of Volcanic Action—continued. II. Subterranean Movements of the Magma: i. Dykes and Veins; ii. Sills and Laccolites; iii. Bosses (Stocks, Culots), Conditions that govern the Intrusion of Molten Rock within the Terrestrial Crust 77

CHAPTER VII

Influence of Volcanic Rocks on the Scenery of the Land—Effects of Denudation 100

BOOK II VOLCANIC ACTION IN PRE-CAMBRIAN TIME

CHAPTER VIII Pre-Cambrian Volcanoes

The Beginnings of Geological History—Difficulties in fixing on a generally applicable Terminology—i. The Lewisian (Archæan) Gneiss; ii. The Dalradian or Younger Schists of Scotland; iii. The Gneisses and Schists of Anglesey; iv. The Uriconian Volcanoes; v. The Malvern Volcano; vi. The Charnwood Forest Volcano 109

BOOK III THE CAMBRIAN VOLCANOES CHAPTER IX Characteristics of the Cambrian System in Britain

The Physical Geography of the Cambrian Period—The Pioneers of Palæozoic Geology in Britain—Work of the Geological Survey in Wales—Subdivisions of the Cambrian System in Britain 139

CHAPTER X

The Cambrian Volcanoes of South Wales 145

CHAPTER XI

The Cambrian Volcanoes of North Wales, the Malvern Hills and Warwickshire 159

BOOK IV THE SILURIAN VOLCANOES

CHAPTER XII Characters of the Silurian System in Britain. The Arenig Volcanoes

The Land and Sea of Silurian time—Classification of the Silurian System—General Petrography of the Silurian Volcanic Rocks—I. The Eruptions of Arenig Age 173

CHAPTER XIII The Eruptions of Llandeilo and Bala Age

i. The Builth Volcano—ii. The Volcanoes of Pembrokeshire—iii. The Caernarvonshire Volcanoes of the Bala Period—iv. The Volcanic District of the Berwyn Hills—v. The Volcanoes of Anglesey—vi. The Volcanoes of the Lake District; Arenig to close of Bala Period—vii. Upper Silurian (?) Volcanoes of Gloucestershire 202

CHAPTER XIV

The Silurian Volcanoes of Ireland 239

BOOK V THE VOLCANOES OF DEVONIAN AND OLD RED SANDSTONE TIME CHAPTER XV

The Devonian Volcanoes 257

CHAPTER XVI The Volcanoes of the Old Red Sandstone

Geological Revolutions at the close of the Silurian Period Physical Geography of the Old Red Sandstone—Old Lake-basins, their Flora and Fauna—Abundance of Volcanoes—History of Investigation in the Subject 263

CHAPTER XVII

Distribution of the Volcanic Centres in the Lower Old Red Sandstone—Characters of the Materials Erupted by the Volcanoes 271

CHAPTER XVIII

Structure and Arrangement of the Lower Old Red Sandstone Volcanic Rocks in the Field 281

CHAPTER XIX Volcanoes of the Lower Old Red Sandstone of "Lake Caledonia"

Description of the several Volcanic Districts: "Lake Caledonia," its Chains of Volcanoes—The Northern Chain: Montrose Group—Ochil and Sidlaw Hills—the Arran and Cantyre Centre—the Ulster Centre 294

CHAPTER XX Volcanoes of the Lower Old Red Sandstone of "Lake Caledonia"—continued

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