distinct provinces of animals and plants have not become more blended to-

gether-Brocchi's speculations on the loss of species-Stations of plants and

animals--Complication of causes on which they depend—Stations of plants,

how affected by animals-Equilibrium in the number of Species, how pre-

served-Peculiar efficacy of insects in this task-Rapidity with which certain

insects multiply, or decrease in numbers-Effect of omnivorous animals in

preserving the equilibrium of species-Reciprocal influence of aquatic and

terrestrial species on each other

CHAPTER IX.

The circumstances which constitute the Stations of Animals are change-

able-Extension of the range of one species alters the condition of others-

Supposed effects which may have followed the first entrance of the Polar

Bears into Iceland-The first appearance of a new species in a region causes

the chief disturbance-Changes known to have resulted from the advance of

human population-Whether man increases the productive powers of the

earth-Indigenous Quadrupeds and Birds of Great Britain known to have

been extirpated-Extinction of the Dodo-Rapid propagation of the domestic

Quadrupeds over the American Continent-Power of exterminating species

no prerogative of Man-Concluding Remarks

CHAPTER X.

Influence of inorganic causes in changing the habitations of species-

Powers of diffusion indispensable, that each species may maintain its ground

—How changes in the physical geography affect the distribution of species—

Rate of the change of species cannot be uniform, however regular the action

of the inorganic causes-Illustration derived from subsidences by earthquakes

-from the elevation of land by the same-from the formation of new islands

-from the wearing through of an isthmus-Each change in the physical

geography of large regions must occasion the extinction of species-Effects

of a general alteration of climate on the migration of species-Gradual refri-

geration causes species in the northern and southern hemispheres to become

distinct-Elevation of temperature the reverse-Effects in the distribution of

species which must result from vicissitudes in climate inconsistent with the

theory of transmutation .

CHAPTER XI.

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141

. 158

Theory of the successive extinction of species consistent with their limited

geographical distribution-The discordance in the opinions of botanists re-

specting the centres from which plants have been diffused may arise from

changes in physical geography subsequent to the origin of living species

-Whether there are grounds for inferring that the loss from time to

time of certain animals and plants is compensated by the introduction of

PAGE

new species?-Whether any evidence of such new creations could be expected

within the historical era, even if they had been as frequent as cases of extinc-

tion?-The question whether the existing species have been created in suc-

cession can only be decided by reference to geological monuments

CHAPTER XII.

Effects produced by the powers of vitality on the state of the earth's sur-

face-Modifications in physical geography caused by organic beings on dry

land inferior to those caused in the subaqueous regions-Why the vegetable

soil does not augment in thickness-Organic matter drifted annually to the

sea, and buried in subaqueous strata-Loss of nourishment from this source,

how supplied-The theory, that vegetation is an antagonist power counterba-

lancing the degradation caused by running water, untenable-That the

igneous causes are the true antagonist powers, and not the action of animal

and vegetable life-Conservative influence of vegetation—Its bearing on the

theory of the formation of valleys, and on the age of the cones of certain

extinct volcanos-Rain diminished by the felling of forests-Distribution of

the American forests dependent on the direction of the predominant winds-

Influence of man in modifying the physical geography of the globe.

CHAPTER XIII.

Effects produced by the action of animal and vegetable life on the material

constituents of the earth's crust-Imbedding of organic remains in deposits

on emerged land-Growth of Peat-Peat abundant in cold and humid cli-

mates—Site of many ancient forests in Europe now occupied by Peat-

Recent date of many of these changes-Sources of Bog Iron-ore-Preserva-

tion of animal substances in Peat-Causes of its antiseptic property-Miring

of quadrupeds-Bursting of the Solway Moss-Bones of herbivorous qua-

drupeds found in Peat-Imbedding of animal remains in Caves and Fissures

-Formation of bony breccias-Human bones and pottery intermixed with

the remains of extinct quadrupeds in caves in the South of France-Infer-

ences deducible from such associations

CHAPTER XIV.

Imbedding of organic remains in alluvium and the ruins caused by land-

slips-Effects of sudden inundations-Of landslips-Terrestrial animals most

abundantly preserved in alluvium and landslips, where earthquakes pre-

vail-Erroneous theories which may arise from overlooking this circum-

stance-On the remains of works of art included in alluvial deposits-Imbed-

ding of organic bodies and human remains in blown sand-Temple of Ipsam-

bul on the Nile-Dried carcasses of animals buried in the sands of the

African deserts-Towns overwhelmed by sand-floods in England and France

176

185

209

-Imbedding of organic bodies and works of art in volcanic formations on

the land-Cities and their inhabitants buried by showers of ejected matter

-by lava-In tuffs or mud composed of volcanic sand and ashes

CHAPTER XV.

Imbedding of organic remains in subaqueous deposits-Division of the sub-

ject-Phenomena relating to terrestrial animals and plants first considered-

Wood sunk to a great depth in the sea instantly impregnated with salt-water

-Experiments of Scoresby-Drift timber carried by the Mackenzie into Slave

Lake and into the sea-Cause of the abundance of drift timber in this

river-Floating trees in the Mississippi-In the Gulf stream-Immense

quantity thrown upon the coast of Iceland, Spitzbergen, and Labrador-Im-

bedding of the remains of insects-of the remains of reptiles-Why the bones

of birds are so rare in subaqueous deposits-Imbedding of terrestrial quadru-

peds-Effects of a flood in the Solway Firth-Wild horses annually drowned

in the savannahs of South America-Skeletons in recent shell marl-Drifting

of mammiferous and other remains by tides and currents

CHAPTER XVI.

Imbedding of the remains of man and his works in subaqueous strata-

Drifting of bodies to the sea by river-inundations—Destruction of bridges and

houses-Burial of human bodies in the sea-Loss of lives by shipwreck-

Circumstances under which human corpses may be preserved under a great

thickness of recent deposits-Number of wrecked vessels-Durable character

of many of their contents-Examples of fossil skeletons of men-Of fossil

canoes, ships, and works of art—Of the chemical changes which certain

metallic instruments have undergone after long submergence-Effects of the

subsidence of land in imbedding cities and forests in subaqueous strata—

Earthquake of Cutch in 1819-Submarine forests-Berkely's arguments for

the recent date of the creation of man-Concluding remarks

CHAPTER XVII.

Imbedding of aquatic species in subaqueous strata-Inhumation of fresh-

water plants and animals-Shell marl-Fossilized seed-vessels and stems of

Chara-Recent deposits in the American lakes-Fresh-water species drifted

into seas and estuaries-Lewes levels-Alternations of marine and fresh-

water strata, how caused-Imbedding of marine plants and animals—

Cetacea stranded on our shores-Their remains should be more conspicuous

in marine alluvium than the bones of land quadrupeds-Liability of littoral

and estuary testacea to be swept into the deep sea-Effects of a storm in the

Frith of Forth-Burrowing shells secured from the ordinary action of waves

and currents-Living testacea found at considerable depths

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CHAPTER XVIII.

Formation of coral reefs-They are composed of shells as well as corals-

Conversion of a submerged reef into an island-Extent and thickness of coral

formations-The Maldiva isles-Growth of coral not rapid-Its geological

importance-Circular and oval forms of coral islands-Shape of their lagoons

-Causes of their peculiar configuration-Openings into the lagoons-Why

the windward side both in islands and submerged reefs is higher than the

leeward-Stratification of coral formations-Extent of some reefs in the

Pacific-That the subsidence by earthquakes in the Pacific exceeds the ele-

vation due to the same cause-Elizabeth, or Henderson's Island-Coral and

shell limestones now in progress, exceed in area any known group of ancient

rocks-The theory that all limestone is of animal origin, considered-The

hypothesis that the quantity of calcareous matter has been and is still on the

increase, controverted

283

ERRATA.

Frontispiece, for Montagnola read Montagnuola.

Page 39, line 2 from the bottom, for excusively read exclusively.

PRINCIPLES OF GEOLOGY.

CHAPTER I.

Changes of the Organic World now in progress-Division of the subject-Examination of the question, Whether Species have a real existence in Nature? -Importance of this question in Geology-Sketch of Lamarck's arguments in favour of the Transmutation of Species, and his conjectures respecting the Origin of existing Animals and Plants-His Theory of the transformation of the Orang Outang into the Human Species.

In our first volume we treated of the changes which have taken place in the inorganic world within the historical era, and we must next turn our attention to those now in progress in the animate creation. In examining this class of phenomena, we shall treat first of the vicissitudes to which species are subject, and afterwards consider the influence of the powers of vitality in modifying the surface of the earth and the material constituents of its crust.

The first of these divisions will lead us, among other topics, to inquire, first, whether species have a real and permanent existence in nature; or whether they are capable, as some naturalists pretend, of being indefinitely modified in the course of a long series of generations? Secondly, whether, if species have a real existence, the individuals composing them have been derived originally from many similar stocks, or each from one only, the descendants of which have spread themselves gradually from a particular point over the habitable lands and waters? Thirdly, how far the duration of each species of animal and plant is limited by its dependance on certain fluctuating and temporary conditions in the state of the animate and inanimate VOL. II.

B