CONTENTS.

CHAPTER I.

THE STORY OF A PIECE OF GRANITE.

Discussions on the origin of granite-Plutonists and Nep-
tunists-Victory of the former-Result of carrying the
victory too far-Mineralogical composition of granite-
Quartz, its component parts-Alkaline ingredients probably
assisted in its fluxion-Felspar, what it is composed of-Its
"rottenness"-Origin of Kaolin, or "China-clay "—Mica,
description of-Hornblende, its colours, chemical composition,
&c.—Mineralogical relations of granite-Porphyry, origin of
its name-Relation of ditto to other igneous rocks-Syenite
-Protogine-Pegmatite-Binary granites-Ternary ditto-
Quaternary ditto - Their classification-The first formed
crust of the globe-Idea as to the origin of the metamorphic
rocks-Conditions under which granites were originally for-
med-Cavities in the quartz crystals of granite-Heat and
water concerned in origin of granite-Pressure under which
granite was formed-Consequences of absence of pressure on
igneous rocks-The granites of the Highlands-Pressure
under which they were formed-Ditto of the granites of
Cornwall-Difference of rock-pressure-Great antiquity of
the earth proved by above facts-Granite probably formed
of re-melted stratified rocks-Deep-seated condition of latter
-Upheaval of granite nucleus of mountains-How it is
granite now occupies large areas-The denudation of rocks
formerly overlying granite outcrops-Internal force of the
earth as opposed to that of the sun-Overlying rocks strip-
ped off by atmospheric agencies-Time occupied

PAGE

1-13

CHAPTER II.

THE STORY OF A PIECE OF QUARTZ.

PAGE

Time as a factor in Geology-Astronomical calculations--Our

notions of the earth's antiquity greatly expanded within last

ten years The Cambrian period-"Primary" rocks-Pos-

sibly older stratified rocks than any yet known-Quartz

rock, its external appearance-Crystals of ditto-Quartz and

Quartzite-Difference of ditto-" Brazilian pebbles"- The

Laurentian period the oldest yet known-Composition of

Quartz-How difference in colour was effected—Amethyst—

Topaz-Cairngorms— Jasper--Flint— Chalcedony—Agates—

The metamorphic rocks-Former notion of ditto-Absence

of fossils in ditto-Notion as to the Cambrian period-

Altered rocks-Cause of ditto-Poverty of species of organic

forms in older rocks-What quartz originally was-How

formed-The Eozoon, or 66 Dawn-animalcule "-Organiza-

tion of ditto-Its natural history habits-Recollections of a

Piece of Quartz-Plumbago, or
66 black-lead"-How formed

-Lowly organization of earlier land plants-The Laurentian

limestones-How they were probably formed-Phosphates of

lime-Thickness of lower Laurentian rocks-Changes during

Laurentian period-Elevation of marine deposits into dry

land- A period of submergence-The upper Laurentian

rocks-How formed- Unconformability" illustrated-In-

ferences from such phenomena-Changes through which

Laurentian rocks have passed-Denudations of ditto-In-

trusions of igneous rocks in ditto-Metamorphism of sand-

stones, limestones, &c.-Contortion of rocks
14-23

CHAPTER III.

THE STORY OF A PIECE OF SLATE.

Locality of slate rocks-Scenery of the Welsh mountains-
Original condition of latter-Difference in mode of formation
of sandstone and limestone rocks-" Cleavage," what it is-
Probable cause of ditto-Joints" in slate rocks-Contortions
in Cambrian rocks-Wear and tear of ditto-Origin of the
contortions, &c.-Experiments on rock contortion-- The Pro-
tozoic period, what it was thought to be-Age of Cambrian

rocks-Fossils of ditto-Laws of the succession of life-forms

-Lowly organization of Cambrian fauna and flora-Thick-

ness of Cambrian rocks-Composition of ditto-Evidences of

shallow sea deposition-How such a thickness of rock ma-

terial could thus be formed-Arencolites, or fossil worm-

borings-Ripple-marks in Cambrian strata-Rain-pittings

and sun-cracks in ditto-The first crustaceans-Zoophytes

of the Cambrian seas-The Lower Cambrian formation as a

group of rocks-Break in continuity of Cambrian rocks-

Absence of a great limestone deposit-Where latter will

possibly be found-The upper Cambrian rocks—Lingula

flags-The brachiopodous mollusca-Antiquity of certain

forms of life-Fossil shrimps-Ancient sea-lilies-Habits of

ditto-The Trilobites - Pteropods-Why Cambrian fossils

are found as "casts"-Influx of higher forms of life-The

Cephalopodous mollusca-Orthoceratites — Gasteropoda, or

marine snails-The Bellerophon-Paucity in specific types

—Progression of life system-Inference from ditto

CHAPTER IV.

THE STORY OF A PIECE OF LIMESTONE.

PAGE

24-36

Limestones common to every geological formation-Generally
of vital origin-Evidences of deep sea origin-Characterized
by abundance of marine organisms-Sandstones contain more
terrestrial ditto-Silurian limestones in the "Black Country"
-The Wren's nest. Dudley-Abundance of fossils-Silurian
limestones in America-Origin of Petroleum, or "rock-
oil"-The Wenlock limestones-Trilobites, abundance of
species of Alternations in stratification of Silurian rocks
-Shingle-beds-Thickness of Silurian rocks-Greater dis-
tribution of sea areas—Probable height of mountains-The
Lower Silurian rocks-Evidences of volcanic disturbances
-Bala limestones-Ca adoc sandstones-- The Middle Si-
lurian rocks May Hill sandstones - Tarannon shales
Upper Silurian rocks- Their thickness, &c. - Woolhope
beds Wenlock limestones and shale - Ludlow beds -
Aymestry limestones-Downton sandstones-Marine ani-
mals of the Silurian period-Orthoceratites-"Sea-pens"-
Graptolites-Structure of the Trilobites-Inferences of ditto

--

PAGE

-Great change in physical geography during Middle Si-
lurian period-Thickness of volcanic lava and ash beds-
Abundance of marine life during Upper Silurian times-
Pectens-Univalves Cystideans - The "chain-coral
Ancient coral reefs in Shropshire, &c.-Favosites polymorpha
-Brachiopodous mollusca of Silurians--First appearance of
Vertebrate animals as fishes-Ancient feeding-grounds of
ditto The Ludlow "Bone-bed "-Recent bone-bed off the
Irish coasts-Presence of fossil spores of cryptogamous plants
in Ludlow bone-bed-Inferences from ditto-Origin of metal
lodes-Usual preponderance of gold in Silurian rocks, &c. 37-57

CHAPTER V.

THE STORY OF A PIECE OF SANDSTONE.

Sandstone beds in every geological formation-Psychometry—
How sandstone rocks were originally formed-The physical
changes that have taken place since-Principal agents in
formation of sandstones-Origin of Old Red Sandstone-
Cementing agents in sandstone rocks-Free-stones and flag-
stones-The Devonian period-Rocks of ditto in America,
South Africa, Russia, Asia-minor, and Australia-Origin of
the name Old Red Sandstone-Thickness of ditto-Divisions
of ditto-Varying thickness in different localities-Error as
to greater prevalence of Carbonic acid in atmosphere during
Paleozoic epoch-How the rocks were coloured red-Ancient
sea-weeds-Huge Crustaceans-Pterygotus—" Age of fishes'
-Structure of first order that appeared, the Ganoids-Rela-
tion of ditto to existing species in America and elsewhere-The
Asterolepis - Holoptychius― Pterichthys—Cephalaspis-Coc-
costeus, &c.-External peculiarities of ganoid fishes-The
Placoid fishes-Onchus-Fossil fishes of Caithness, &c,-
Shoals of fossil fish-How accumulated-Reptilian characters
of some Devonian fishes-Corals, Trilobites, &c.-Differences
in physical condition of old sea-bottom-Chief localities of
Devonian fossiliferous strata-Total number of species-The
"Pilton group"-Brachiopodous shells-Spirifer—Clymenia
-"Sun-corals," &c.-Coloured fossil corals of Torquay, &c.
-Peculiar Trilobites of Devonian rocks-Devonian rocks in
Ireland-Evidences of fresh-water deposition-The "Irish