CONTENTS.

CHAPTER I.

PAGE

Scene near Colinton in midsummer—A grey travelled Boulder—Its aspect and contents—Its story of the past,

CHAPTER II.

Exterior of the boulder—Travelled stones a difficult problem—Once referred to the Deluge—Other theories—Novelty of the true solution—Icebergs formed in three ways—Progress and scenery of an iceberg—Its effects—Size of icebergs—Boulder clay had a glacial origin—This explanation confirmed by fossil shells—Laws of the distribution of life—Deductions,

CHAPTER III.

How the boulder came to be one—"Crag and tail"—Scenery of central Scotland: Edinburgh—"Crag and tail" formerly associated in its origin with the boulder-clay—This explanation erroneous—Denudation an old process—Its results—Illustration from the Mid-Lothian coal-field—The three Ross-shire hills—The Hebrides relics of an ancient land—Scenery of the western coast—Effects of the breakers—Denudation of the Secondary strata of the Hebrides—Preservative influence of trap-rocks—Lost species of the Hebrides—Illustration—Origin of the general denudation of the country—Illustrative action of streams—Denudation a very slow process—Many old land-surfaces may have been effaced—Varied aspect of the British Islands during a period of submergence—Illustration,

CHAPTER IV.

Interior of the boulder—Wide intervals of Geology—Illustration—Long interval between the formation of the boulder as part of a sand-bed, and its striation by glacial action—Sketch of the intervening ages—The boulder a Lower Carboniferous rock—Cycles of the astronomer and the geologist contrasted—Illustration—Plants shown by the boulder once grew green on land—Traces of thatancient land Its seas, shores, forests, and lakes, all productive of material aids to our comfort and power—Plants of the Carboniferous era—Ferns—Tree-ferns—Calamites—Asterophyllites—Lepidodendron—Lepidostrobus—Stigmaria—Scene in a ruined palace—Sigillaria—Coniferæ, Cycadeæ—Antholites, the oldest known flower—Grade of the Carboniferous flora—Its resemblance to that of New Zealand,

CHAPTER V.

Scenery of the carboniferous forests—Contrast in the appearance of coal districts at the present day—Abundance of animal life in the Carboniferous era—Advantages of palæontology over fossil-botany—Carboniferous fauna—Actiniæ—Cup-corals—Architecture of the present day might be improved by study of the architecture of the Carboniferous period—Mode of propagation of corals—A forenoon on the beach—Various stages in the decomposition of shells—Sea-mat—Bryozoa—Fenestella—Retepora—Stone-lilies—Popular superstitions—Structure of the stone-lilies—Aspect of the sea-bottom on which the stone-lilies flourished—Sea-urchins—Crustacea, their high antiquity—Cyprides—Architecture of the Crustacea and mollusca contrasted—King-crabs,

CHAPTER VI.

Carboniferous fauna continued—George Herbert's ode on "Man"—His idea of creation—What nature teaches on this subject—Molluscous animals—Range of species in time proportionate to their distribution in space—Two principles of renovation and decay exhibited alike in the physical world and the world of life—Their effects—The mollusca—Abundantly represented in the carboniferous rocks—Pteropods—Brachiopods—Productus—Its alliance with Spirifer—Spirifer—Terebratula—Lamellibranchs—Gastropods—Land-snail of Nova Scotia—Cephalopods—Structure of orthoceras—Habits of living nautilus,

CHAPTER VII.

Classification of the naturalist not always correspondent with the order of nature—Incongruous grouping of animals in the invertebrate division—Rudimentary skeleton of the cephalopods—Introduction of the vertebrate type into creation—Ichthyolites of the carboniferous rocks—Their state of keeping—Classification of fossil fishes—Placoids—Ichthyodorulites—Ganoids—Their structure exemplified in the megalichthys and holoptychius—Cranium of megalichthys—Its armature of scales—Microscopic structure of a scale—Skeleton of megalichthys—History of the discovery of the holoptychius—Confounded with megalichthys—External ornament of holoptychius—Its jaws and teeth—Microscopic structure of the teeth—Paucity of terrestrial fauna in coal measures—Insect remains—Relics of reptiles—Concluding summary of the characters of the Carboniferous fauna—Results,

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CHAPTER VIII.

Sand and gravel of the boulder—What they suggested—Their consideration leads us among the more mechanical operations of Nature—An endless succession of mutations in the economy of the universe—Exhibited in plants In animals—In the action of winds and oceanic currents—Beautifully shown by the ceaseless passage of water from land to sea, and sea to land—This interchange not an isolated phenomenon—How aided in its effects by a universal process of decay going on wherever a land surface is exposed to the air—Complex mode of Nature's operations—Interlacing of different causes in the production of an apparently single and simple effect—Decay of rocks—Chemical changes—Underground and surface decomposition—Carbonated springs—The Spar Cave—Action of rain-water—Decay of granite—Scene in Skye—Trap-dykes—Weathered cliffs of sandstone—Of conglomerate—Of shale—Of limestone—Caverns of Raasay—Incident—Causes of this waste of calcareous rocks—Tombstones,

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CHAPTER IX.

Mechanical forces at work in the disintegration of rocks—Rains—Landslips—Effects of frosts—Glaciers and icebergs—Abrading power of rivers—Suggested volume on the geology of rivers—Some of its probable contents—Scene in a woody ravine—First idea of the origin of the ravine one of primeval cataclysms—Proved to be incorrect—Love of the marvellous long the bane of geology—More careful examination shows the operations of Nature to be singularly uniform and gradual—The doctrine of slow and gradual change not less poetic than that of sudden paroxysms—The origin of the ravine may be sought among some of the quieter processes of Nature—Features of the ravine Lessons of the waterfall—Course of the stream through level ground—True history of the ravine—Waves and currents—What becomes of the waste of the land—The Rhone and the Leman Lake—Deltas on the sea-margin—Reproductive effects of currents and waves—Usual belief in the stability of the land and the mutability of the ocean—The reverse true—Continual interchange of land and sea part of the economy of Nature—The continuance of such a condition of things in future ages rendered probable by its continuance during the past,

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CHAPTER X.

The structure of the stratified part of the earth's crust conveniently studied by the examination of a single formation—A coal-field selected for this purpose—Illustration of the principles necessary to such an investigation—The antiquities of a country of value in compiling its pre-historic annals—Geological antiquities equally valuable and more satisfactorily arranged—Order of superpositionof stratified formations—Each formation contains its own suite of organic remains—The age of the boulder defined by this test from fossils—Each formation as a rule shades into the adjacent ones—Mineral substances chiefly composing the stratified rocks few in number—Not of much value in themselves as a test of age—The Mid-Lothian coal-basin—Its subdivisions—The limestone of Burdiehouse—Its fossil remains—Its probable origin—Carboniferous limestone series of Mid-Lothian—Its relation to that of England—Its organic remains totally different from those of Burdiehouse—Structure and scenery of Roman Camp Hill—Its quarries of the mountain limestone—Fossils of these quarries indicative of an ancient ocean-bed—Origin of the limestones—Similar formations still in progress—Coral-reefs and their calcareous silt—Sunset among the old quarries of Roman Camp Hill,

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CHAPTER XI.

Intercalation of coal seams among mountain limestone beds of Mid-Lothian—North Greens seam—Most of our coal seams indicate former land-surfaces—Origin of coal a debated question—Erect fossil trees in coal-measures—Deductions to be drawn therefrom—Difference between the mountain limestone of Scotland and that of England—Coal-bearing character of the northern series—Divisions of the Mid-Lothian coal-field—The Edge coals—Their origin illustrated by the growth of modern deltas—Delta of the Nile—Of the Mississippi—Of the Ganges—Progress of formation of the Edge coals—Scenery of the period like that of modern deltas—Calculations of the time required for the growth of a coal-field—Why of doubtful value—Roslyn Sandstone group—Affords proofs of a general and more rapid subsidence beneath the sea—Its great continuity—Probable origin—Flat coals—Similar in origin to the Edge coals below—Their series not now complete—Recapitulation of the general changes indicated by the Mid-Lothian coal-field,

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CHAPTER XII.

Trap-pebbles of the boulder—Thickness of the earth's crust unknown—Not of much consequence to the practical geologist—Interior of the earth in a highly heated condition—Proofs of this—Granite and hypogene rocks—Trap-rocks: their identity with lavas and ashes—Scenery of a trappean country—Subdivisions of the trap-rocks—Intrusive traps—Trap-dykes—Intrusive sheets—Salisbury Crags—Traps of the neighbourhood of Edinburgh—Amorphous masses—Contemporaneous trap-rocks of two kinds—Contemporaneous melted rocks—Tests for their age and origin—Examples from neighbourhood of Edinburgh—Tufas or volcanic ashes—Their structure and origin—Example of contemporaneous trap-rocks—Mode of interpreting them—Volcanoes of Carboniferous times—Conclusion,

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