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]

LIST OF ILLUSTRATIONS

FIG.PAGE
1.Vesicular structure, Lava from Ascension Island, slightly less than natural size[15]
2.Elongation and branching of steam-vesicles in a lava, Kilninian, Isle of Mull, a little less than natural size[17]
3.Microlites of the Pitchstone of Arran (magnified 70 diameters)[19]
4.Perlitic structure in Felsitic Glass, Isle of Mull (magnified)[19]
5.Spherulitic structure (magnified)[19]
6.Micropegmatitic or Granophyric structure in Granophyre, Mull (magnified)[20]
7.Ophitic structure in Dolerite, Gortacloghan, Co. Derry (magnified)[20]
8.Variolitic or orbicular structure, Napoleonite, Corsica (nat. size)[22]
9.Flow-structure in Rhyolite, Antrim, slightly reduced[23]
10.Lumpy, irregular trachytic lava-streams (Carboniferous), East Linton, Haddingtonshire[24]
11.View at the entrance of the Svinofjord, Faroe Islands, illustrating the terraced forms assumed by basic lavas[25]
12.Sack-like or pillow-form structure of basic lavas (Lower Silurian), Bennan Head, Ballantrae, Ayrshire[26]
13.Alternations of coarser and finer Tuff[34]
14.Alternations of Tuff with non-volcanic sediment[35]
15.Ejected block of basalt which has fallen among Carboniferous shales and limestones, shore, Pettycur, Fife[37]
16.Effects of denudation on a Vesuvian cone[40]
17.Section to illustrate the structure of the Plateau type[43]
18.Diagram illustrating the structure and denudation of Puys[45]
19.Section illustrating submarine eruptions; alternations of lavas and tuffs with limestones and shales full of marine organisms[48]
20.Diagram illustrating volcanic eruptions on a river-plain[49]
21.Diagram illustrating volcanic eruptions on a land-surface[50]
22.Ground-plans of some volcanic vents from the Carboniferous districts of Scotland[55]
23.View of an old volcanic "Neck" (The Knock, Largs, Ayrshire, a vent of Lower Carboniferous age)[56]
24.Section of neck of agglomerate, rising through sandstones and shales[58]
25.Neck filled with stratified tuff[64]
26.Section of neck of agglomerate with plug of lava[65]
27.Section of agglomerate neck with dykes and veins[66]
28.Section of neck filled with massive rock[68]
29.Successive shiftings of vents giving rise to double or triple cones[70]
30.Section to show the connection of a neck with a cone and surrounding bedded tuffs[71]
31.Diagram illustrating the gradual emergence of buried volcanic cones through the influence of prolonged denudation [75]
32.Dyke, Vein, and Sill[80]
33.Section of Sill or Intrusive Sheet[83]
34.Ideal section of three Laccolites. (After Mr. Gilbert)[86]
35.Diagram illustrating the stratigraphical relations of the pre-Cambrian and Cambrian rocks of the North-west Highlands of Scotland[112]
36.Map of a portion of the Lewisian gneiss of Ross-shire[118]
37.Section showing the position of sills in the mica-schist series between Loch Tay and Amulree[124]
38.Sketch of crushed basic igneous rock among the schists, E. side of Porth-tywyn-mawr, E. side of Holyhead Straits[128]
39.Section across the Uriconian series of Caer Caradoc[132]
40.Map of the volcanic district of St. David's[146]
41.Section showing the interstratification of tuff and conglomerate above Lower Mill, St. David's[154]
42.Basic dyke traversing quartz-porphyry and converted into a kind of slate by cleavage. West side of Llyn Padarn[162]
43.Section of well-cleaved tuff, grit and breccia passing up into rudely-cleaved conglomerate and well-bedded cleaved fine conglomerate and grit. East side of Llyn Padarn[163]
44.Section of Clegyr on the north-east side of Llyn Padarn, near the lower end[164]
45.Section across the Cambrian formations of the Malvern Hills, showing the position of the intercalated igneous rocks. After Phillips[170]
46.Section across Rhobell Fawr[178]
47.Section at the Slate Quarry, Penrhyn Gwyn, north slopes of Cader Idris[180]
48.Sketch-section across Cader Idris[182]
49.Section across the Moelwyn Range[185]
50.Section across the anticline of Corndon[190]
51.Structure in finely-amygdaloidal diabase lava, south of mouth of Stinchar River, Ayrshire[193]
52.View of Knockdolian Hill from the east[194]
53.Section across the Lower Silurian volcanic series in the south of Ayrshire (B. N. Peach)[197]
54.Section of part of the Arenig volcanic group, stream south of Bennane Head, Ayrshire[198]
55.Flow-structure in the lowest felsite on the track from Llanberis to the top of Snowdon[211]
56.Section of Snowdon[212]
57.Section across the Berwyn Hills. (Reduced from Horizontal Section, Geol. Surv. Sheet 35)[219]
58.Section of the strata on the shore at Porth Wen, west of Amlwch[223]
59.Section of intercalated black shale in the volcanic series at Porth yr hwch, south of Carmel Point, Anglesey[224]
60.Green slates overlain with volcanic breccia, Carmel Point[224]
61.Blue shale or slate passing into volcanic breccia east of Porth Padrig, near Carmel Point[225]
62.Section of felsites in the Coniston Limestone group, west of Stockdale[232]
63.Fine tuff with coarser bands near Quayfoot Quarries, Borrowdale[234]
64.Diagram of the general relations of the different groups of rock in the Lower Silurian volcanic district along the western shore of Lough Mask[253]
65.Veins and nests of sandstone due to the washing of sand into fissures and cavities of an Old Red Sandstone lava. Turnberry Point, Ayrshire[283]
66.Ground-plan of reticulated cracks in the upper surface of an Old Red Sandstone lava filled in with sandstone. Red Head, Forfarshire[284]
67.Section across the volcanic series of Forfarshire [286]
68.Section across two necks above Tillicoultry, Ochil Hills[288]
69.Section of the granite core between Merrick and Corscrine[290]
70.Section across the three Dirrington Laws, Berwickshire[291]
71.Section of Papa Stour, Shetlands, showing sill of spherulitic felsite traversing Old Red Sandstone and bedded porphyrites (Messrs. Peach and Horne)[292]
72.Section across Northmavine, from Okrea Head to Skea Ness, Shetland, showing dykes and connected sill of granite and felsite (Messrs. Peach and Horne)[292]
73.Section at the edge of one of the bays of Lower Old Red Sandstone along the northern margin of Lake Caledonia, near Ochtertyre[295]
74.Craig Beinn-nan-Eun (2067 feet), east of Uam Var, Braes of Doune. Old Red Conglomerate, with the truncated ends of the strata looking across into the Highlands; moraines of Corry Beach in the foreground[296]
75.Section showing the top of the volcanic series at the foot of the precipice of the Red Head, Forfarshire[300]
76.Andesite with sandstone veinings and overlying conglomerate. Todhead, south of Caterline, coast of Kincardineshire[303]
77.Section across the Boundary-fault of the Highlands at Glen Turrit, Perthshire[305]
78.Section across the chain of the Sidlaw Hills near Kilspindie[306]
79.Section across the Eastern Ochil Hills from near Newburgh to near Auchtermuchty[307]
80.Generalized section across the heart of the Ochil Hills from Dunning on the north to the Fife coal-field near Saline on the south[308]
81.Diagram of the volcanic series of the Western Ochil Hills[309]
82.View of Cnoc Garbh, Southend, Campbeltown. A volcanic neck of Lower Old Red Sandstone age, about 400 yards wide in its longer diameter[312]
83.Section of volcanic series on beach, Southend, Campbeltown[313]
84.Section of the base of the volcanic series, Reclain, five miles south of Pomeroy[316]
85.Section of shales and breccias at Crossna Chapel, north-east of Boyle[316]
86.Section across the north end of the Pentland Hills, from Warklaw Hill to Pentland Mains. Length about five miles[318]
87.View of the lava-escarpments of Warklaw Hill, Pentland chain, from the north-west[319]
88.Section across the Pentland Hills through North Black Hill and Scald Law. Length about three miles[322]
89.Section from the valley of the Gutterford Burn through Green Law and Braid Law to Eight-Mile Burn[322]
90.Section across the north end of the Pentland Hills, and the southern edge of the Braid Hill vent. Length about two miles[324]
91.Section across the northern end of the Biggar volcanic group, from Fadden Hill to beyond Mendick Hill[326]
92.Section across the southern part of the Biggar volcanic group from Covington to Culter[328]
93.Section from Thankerton Moor across Tinto to Lamington[328]
94.Section across the Duneaton volcanic district from the head of the Duneaton Water to Kirklea Hill[330]
95.Cavernous spaces in andesite, filled in with sandstone, John o' Groats Port, Turnberry, Ayrshire[333]
96.Section of andesites, Turnberry Castle, Ayrshire[334]
97.Lenticular form of a brecciated andesite (shown in [Fig. 96]), Turnberry, Ayrshire[334]
98.Section across the volcanic area of St. Abb's Head (after Prof. J. Geikie)[339]
99.View of terraced andesite hills resting on massive conglomerate, south of Oban[341]
100.Section of lava-escarpment at Beinn Lora, north side of mouth of Loch Etive, Argyllshire[342]
101.Section across Strathbogie, below Rhyme, showing the position of the volcanic band [344]
102.View of Knockfeerina, Limerick, from the north-east—a volcanic neck of Upper Old Red Sandstone age[349]
103.Section of the volcanic zone in the Upper Old Red Sandstone, Cam of Hoy, Orkney[351]
104.Section of the volcanic zone in the Upper Old Red Sandstone at Black Ness, Rackwick, Hoy[351]
105.Section across the volcanic band and its associated necks, Hoy, Orkney[352]
106.Ground-plan of volcanic neck piercing the Caithness Flagstone series on the beach near John o' Groat's House[353]
107.View of the escarpment of the Clyde Plateau in the Little Cumbrae, from the south-west[368]
108.View of the edge of the Volcanic Plateau south of Campbeltown, Argyllshire[370]
109.View of North Berwick Law from the east, a phonolite neck marking one of the chief vents of the Garleton Plateau. (From a photograph)[371]
110.The Bass Rock, a trachytic neck belonging to the Garleton plateau, from the shore at Canty Bay[372]
111.Corston Hill—a fragment of the Midlothian Plateau, seen from the north[373]
112.View of Arthur Seat from Calton Hill to the north[374]
113.View of Arkleton Fell, part of the Solway Plateau, from the south-west[376]
114.Vertical sections of the escarpment of the Clyde plateau from north-east to south-west[384]
115.Section of Craiglockhart Hill, Edinburgh[387]
116.Section of the bottom of the Midlothian Plateau, Linnhouse Water above Mid-Calder Oilworks[387]
117.Section of the top of the Midlothian Plateau in the Murieston Water[388]
118.Section of Calton Hill, Edinburgh[389]
119.Cliff of tuff and agglomerate, east side of Oxroad Bay, a little east from Tantallon Castle, East Lothian[391]
120.Section across part of the Clyde Plateau to the west of Bowling (reduced from Sheet 6 of the Horizontal Sections of the Geological Survey of Scotland)[392]
121.Diagram illustrating the thinning away southwards of the lavas of the Clyde Plateau between Largs and Ardrossan. Length about 10 miles[393]
122.Diagram illustrating the thinning away eastwards of the lavas of the Clyde Plateau in the Fintry Hills. Length about 12 miles[394]
123.View of the two necks Dumgoyn and Dumfoyn, Stirlingshire, taken from the south[395]
124.Ground-plan of Plateau-vents near Strathblane, Stirlingshire, on the scale of 6 inches to a mile[395]
125.Ground-plans of double and triple necks in the Plateau series, on the scale of 6 inches to a mile[396]
126.Ground-plan of tuff-neck, shore east of Dunbar[398]
127.Section across the vents Dumgoyn and Dumfoyn, and the edge of the Clyde plateau above Strathblane, Stirlingshire[400]
128.Section through the large vent of the Campsie Hills[400]
129.Diagrammatic section across the central vent of the Clyde plateau in Renfrewshire[400]
130.Section across Southern Berwickshire, to show the relation of the volcanic plateau to the vents lying south from it[401]
131.Section of south end of Dumbuck Hill. East of Dumbarton[403]
132.Section across the East Lothian plateau, to show the relative position of one of the necks[403]
133.View of Traprain Law from the south, a phonolite neck of the Garleton Plateau[405]
134.Veins and dykes traversing the agglomerate and tuff of the great Renfrewshire vent[408]
135."The Yellow Man," a dyke in volcanic tuff and conglomerate on the shore a little east of North Berwick[409]
136.Trachytic sills, Knockvadie, Kilpatrick Hills [410]
137.Section across the edge of the Clyde plateau, south-east of Beith[411]
138.Section across the upper part of the Clyde plateau at Kilbirnie, Ayrshire[411]
139.Section across the upper surface of the Clyde volcanic plateau, Burnhead, north-west of Kilsyth[412]
140.Section across the upper surface of the Clyde volcanic plateau at Campsie[412]
141.Section across western edge of the Garlton plateau[412]
142.Section across the Solway plateau[413]
143.Section of volcanic vent at East Grange, Perthshire coal-field, constructed by Mr. B. N. Peach from the rocks exposed in a railway-cutting, and from plans of ironstone- and coal-pits[426]
144.View of the Binn of Burntisland—a volcanic neck of agglomerate[428]
145.View of part of the cliffs of vertical agglomerate, Binn of Burntisland[431]
146.Diagram of buried volcanic cone near Dalry, Ayrshire. Constructed from information obtained in mining operations[434]
147.Diagram to illustrate how Volcanic Necks may be concealed and exposed[434]
148.Section across the Saline Hills, Fife[435]
149.Section across the Binn of Burntisland, in an east and west direction[436]
150.Section in old quarry, west of Wester Ochiltree, Linlithgowshire. Calciferous Sandstone series[437]
151.Ejected volcanic block in Carboniferous strata, Burntisland[438]
152.View of volcanic agglomerate becoming finer above east end of Kingswood Craig, two miles east from Burntisland[439]
153.Alternations of basalt and tuff, with shale, etc., of Kingswood Craig, Burntisland[441]
154.Section of the upper surface of a diabase ("leckstone") sheet, Skolie Burn, south-east of Bathgate[443]
155.Section across the volcanic ridge of the Linlithgow and Bathgate Hills, showing the intercalation of limestones that mark important stratigraphical horizons[444]
156.Section in Wardlaw Quarry, Linlithgowshire[445]
157.Section from Linlithgow Loch to the Firth of Forth[446]
158.Section across the Campsie Fells illustrating the contrast between the sills below and above the plateau-lavas[447]
159.Section showing the position of the basic sills in relation to the volcanic series at Burntisland, Fife[448]
160.Sills between shales and sandstones, Hound Point, Linlithgowshire[449]
161.Section of Sill, Cramond Railway, Barnton, near Edinburgh[450]
162.Intrusive dolerite sheet enclosing and sending threads into portions of shale, Salisbury Crags, Edinburgh[452]
163.Intrusive sheet invading limestone and shale, Dodhead Quarry, near Burntisland[452]
164.Spheroidal weathering of dolerite sill, quarry east of North Queensferry, Fife.[455]
165.Two thin sills of "white trap" injected into black carbonaceous shale overlying the Hurlet Limestone, Hillhouse Quarry, Linlithgow[456]
166.Dyke cutting the agglomerate of a neck. Binn of Burntisland[457]
167.Boss of diabase cutting the Burdiehouse Limestone and sending sills and veins into the overlying shales. Railway cutting, West Quarry, East Calder, Midlothian[458]
168.Side of columnar basalt-dyke in the same agglomerate as in [Fig. 166][459]
169.Dyke rising through the Hurlet Limestone and its overlying shales. Silvermine Quarry, Linlithgowshire[460]
170.Junction of amygdaloidal basalt with shales and limestone, shore, half a mile east from Kinghorn, Fife[464]
171.Columnar basalt, Pettycur, Kinghorn, Fife [469]
172.Section across the Fife band of Sills[473]
173.Section across the upper volcanic band of north Ayrshire. Length about four miles[474]
174.Section showing the connection of the two volcanic bands in Liddesdale[476]
175.Diagram to show the position of a mass of Upper Old Red Sandstone which has fallen into the great vent near Tudhope Hill, east of Mosspaul[476]

MAPS

I.General map of the Volcanic districts of the British Isles—[At the end of the volume]
II.Map of the Cambrian and Silurian volcanic region of North Wales [To face p. 256]
III.Map of the Old Red Sandstone volcanic region of "Lake Caledonia"
in Central Scotland and North Ireland [To face p. 334]
IV.Map of the Carboniferous volcanic districts of Scotland [To face p. 476]

BOOK I
GENERAL PRINCIPLES AND METHODS OF INVESTIGATION

CHAPTER I

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.

Among the influences which affected the infancy of mankind, the most potent were those of environment. Whatever in outer nature stimulated or repressed courage, inventiveness, endurance, whatever tended to harden or to weaken the bodily faculties, whatever appealed to the imagination or excited the fancy, became a powerful factor in human development.