_African deserts._--If we attribute the origin of a great part of the

desert of Africa to the gradual progress of moving sands driven eastward

by the westerly winds, we may safely infer that a variety of species

must have been annihilated by this cause alone. The sand-flood has been

inundating, from time immemorial, some of the rich lands on the west of

the Nile; and we have only to multiply this effect a sufficient number

of times in order to understand how, in the lapse of ages, a whole group

of terrestrial animals and plants may become extinct.

The African desert, without including Bornou and Darfour, extends,

according to the calculation of Humboldt, over 194,000 square leagues;

an area nearly three times as great as that of France. In a small

portion of so vast a space, we may infer from analogy that there were

many peculiar species of plants and animals which must have been

banished by the sand, and their habitations invaded by the camel, and by

birds and insects formed for the arid sands.

There is evidently nothing in the nature of the catastrophe to favor the

escape of the former inhabitants to some adjoining province; nothing to

weaken, in the bordering lands, that powerful barrier against

emigration--pre-occupancy. Nor, even if the exclusion of a certain group

of species from a given tract were compensated by an extension of their

range over a new country, would that circumstance tend to the

conservation of species in general; for the extirpation would merely

then be transferred to the region so invaded. If it be imagined, for

example, that the aboriginal quadrupeds, birds, and other animals of

Africa, emigrated in consequence of the advance of drift-sand, and

colonized Arabia, the indigenous Arabian species must have given way

before them, and have been reduced in number or destroyed.

Let us next suppose that, in some central or more elevated parts of the

great African desert, the upheaving power of subterranean movements

should be exerted throughout an immense series of ages, accompanied, at

certain intervals, by volcanic eruptions, such as gave rise at once, in

1755, to a mountain 1600 feet high, on the Mexican plateau. When the

continued repetition of these events had caused a mountain-chain, it is

obvious that a complete transformation in the state of the climate would

be brought about throughout a vast area.

We may imagine the summits of the new chain to rise so high as to be

covered, like Mount Atlas, for several thousand feet, with snow, during

a great part of the year. The melting of these snows, during the

greatest heat, would cause the rivers to swell in the season when the

greatest drought now prevails; the waters, moreover, derived from this

source, would always be of lower temperature than the surrounding

atmosphere, and would thus contribute to cool the climate. During the

numerous earthquakes and volcanic eruptions supposed to accompany the

gradual formation of the chain, there would be many floods caused by the

bursting of temporary lakes, and by the melting of snows by lava. These

inundations might deposit alluvial matter far and wide over the original

sands, as the country assumed varied shapes, and was modified again and

again by the moving power from below, and the aqueous erosion of the

surface above. At length the Sahara might be fertilized, irrigated by

rivers and streamlets intersecting it in every direction, and covered by

jungle and morasses; so that the animals and plants which now people

Northern Africa would disappear, and the region would gradually become

fitted for the reception of a population of species perfectly dissimilar

in their forms, habits, and organization.

There are always some peculiar and characteristic features in the

physical geography of each large division of the globe; and on these

peculiarities the state of animal and vegetable life is dependent. If,

therefore, we admit incessant fluctuations in the physical geography, we

must, at the same time, concede the successive extinction of terrestrial

and aquatic species to be part of the economy of our system. When some

great class of _stations_ is in excess in certain latitudes, as, for

example, in wide savannahs, arid sands, lofty mountains, or inland seas,

we find a corresponding development of species adapted for such

circumstances. In North America, where there is a chain of vast inland

lakes of fresh water, we find an extraordinary abundance and variety of

aquatic birds, fresh-water fish, testacea, and small amphibious

reptiles, fitted for such a climate. The greater part of these would

perish if the lakes were destroyed,--an event that might be brought

about by some of the least of those important revolutions contemplated

in geology. It might happen that no fresh-water lakes of corresponding

magnitude might then exist on the globe; or that, if they occurred

elsewhere, they might be situated in New Holland, Southern Africa,

Eastern Asia, or some region so distant as to be quite inaccessible to

the North American species; or they might be situated within the

tropics, in a climate uninhabitable by creatures fitted for a temperate

zone; or, finally, we may presume that they would be pre-occupied by

_indigenous_ tribes.

A vivid description has been given by Mr. Darwin and Sir W. Parish of

the great droughts which have sometimes visited the Pampas of South

America, for three or four years in succession, during which an

incredible number of wild animals, cattle, horses, and birds, have

perished from want of food and water. Several hundred thousand animals

were drowned in the Parana alone, having rushed into the river to drink,

and being too much exhausted by hunger to escape.[986] Such droughts are

often attended in South America and other hot climates by wide-spreading

conflagrations, caused by lightning, which fires the dried grass and

brush-wood. Thus quadrupeds, birds, insects, and other creatures, are

destroyed by myriads. How many species, both of the animal and vegetable

world, which once flourished in the country between the valley of the

Parana and the Straits of Magellan, may not have been annihilated, since

the first drought or first conflagration began!

To pursue this train of reasoning farther is unnecessary; the geologist

has only to reflect on what has been said of the habitations and

stations of organic beings in general, and to consider them in relation

to those effects which were contemplated in the second book, as

resulting from the igneous and aqueous causes now in action, and he will

immediately perceive that, amidst the vicissitudes of the earth's

surface, species cannot be immortal, but must perish, one after the

other, like the individuals which compose them. There is no possibility

of escaping from this conclusion, without resorting to some hypothesis

as violent as that of Lamarck, who imagined, as we have before seen,

that species are each of them endowed with indefinite powers of

modifying their organization, in conformity to the endless changes of

circumstances to which they are exposed.

_Effects of a general Alteration in Climate on the Distribution of

Species._

Some of the effects which must attend every general alteration of

_climate_ are sufficiently peculiar to claim a separate consideration

before concluding the present chapter.

I have before stated that, during seasons of extraordinary severity,

many northern birds, and in some countries many quadrupeds, migrate

southwards. If these cold seasons were to become frequent, in

consequence of a gradual and general refrigeration of the atmosphere,

such migrations would be more and more regular, until, at length, many

animals, now confined to the arctic regions, would become the tenants of

the temperate zone; while the inhabitants of the temperate zone would

approach nearer to the equator. At the same time, many species

previously established on high mountains would begin to descend, in

every latitude, towards the middle regions; and those which were

confined to the flanks of mountains would make their way into the

plains. Analogous changes would also take place in the vegetable

kingdom.

If, on the contrary, the heat of the atmosphere be on the increase, the

plants and animals of low grounds would ascend to higher levels, the

equatorial species would migrate into the temperate zone, and those of

the temperate into the arctic circle.

But although some species might thus be preserved, every great change of

climate must be fatal to many which can find no place of retreat when

their original habitations become unfit for them. For if the general

temperature be on the rise, then there is no cooler region whither the

polar species can take refuge; if it be on the decline, then the animals

and plants previously established between the tropics have no resource.

Suppose the general heat of the atmosphere to increase, so that even the

arctic region became too warm for the musk-ox, and rein-deer, it is

clear that they must perish; so if the torrid zone should lose so much

of its heat, by the progressive refrigeration of the earth's surface, as

to be an unfit habitation for apes, boas, bamboos, and palms, these

tribes of animals and plants, or, at least; most of the species now

belonging to them, would become extinct, for there would be no warmer

latitudes for their reception.

It will follow, therefore, that as often as the climates of the globe

are passing from the extreme of heat to that of cold--from the summer to

the winter of the great year before alluded to[987]--the migratory

movement will be directed constantly from the poles towards the equator;

and for this reason the species inhabiting parallel latitudes, in the

northern and southern hemispheres, must become widely different. For I

assume, on grounds before explained, that the original stock of each

species is introduced into one spot of the earth only, and,

consequently, no species can be at once indigenous in the arctic and

antarctic circles.

But when, on the contrary, a series of changes in the physical geography

of the globe, or any other supposed cause, occasions an elevation of the

general temperature,--when there is a passage from the winter to one of

the vernal or summer seasons of the great cycle of climate,--then the

order of the migratory movement is inverted. The different species of

animals and plants direct their course from the equator towards the

poles; and the northern and southern hemispheres may become peopled to

a certain limited extent by identical species.

I say limited, because we cannot speculate on the entire transposition

of a group of animals and plants from tropical to polar latitudes, or

the reverse, as a probable or even possible event. We may believe the

mean annual temperature of one zone to be transferable to another, but

we know that the same climate cannot be so transferred. Whatever be the

general temperature of the earth's surface, comparative equability of

heat will characterize the tropical regions; while great periodical

variations will belong to the temperate, and still more to the polar

latitudes. These, and many other peculiarities connected with heat and

light, depend on fixed astronomical causes, such as the motion of the

earth and its position in relation to the sun, and not on those

fluctuations of its surface which may influence the general temperature.

Among many obstacles to such extensive transference of habitations, we

must not forget the immense lapse of time required, according to the

hypothesis before suggested, to bring about a considerable change in

climate. During a period so vast, the other cause of extirpation, before

enumerated, would exert so powerful an influence as to prevent all, save

a very few hardy species, from passing from equatorial to polar regions,

or from the tropics to the pole.[988]

But the power of accommodation to new circumstances is great in certain

species, and might enable many to pass from one zone to another, if the

mean annual heat of the atmosphere and the ocean were greatly altered.

To the marine tribes, especially, such a passage would be possible; for

they are less impeded in their migrations by barriers of land, than are

the terrestrial by the ocean. Add to this, that the temperature of the

ocean is much more uniform than that of the atmosphere investing the

land; so that we may easily suppose that most of the testacea, fish, and

other classes, might pass from the equatorial into the temperate

regions, if the mean temperature of those regions were transposed,

although a second expatriation of these species of tropical origin into

the arctic and antarctic circles would probably be impossible.

Let us now consider more particularly the effect of vicissitudes of

climate in causing one species to give way before the increasing numbers

of some other.

When temperature forms the barrier which arrests the progress of an

animal or plant in a particular direction, the individuals are fewer and

less vigorous as they approach the extreme confines of the geographical

range of the species. But these stragglers are ready to multiply rapidly

on the slightest increase or diminution of heat that may be favorable to

them, just as particular insects increase during a hot summer, and

certain plants and animals gain ground after a series of congenial

seasons.

In almost every district, especially if it be mountainous, there are a

variety of species the limits of whose habitations are conterminous,

some being unable to proceed farther without encountering too much heat,

others too much cold. Individuals, which are thus on the borders of the

regions proper to their respective species, are like the outposts of

hostile armies, ready to profit by every slight change of circumstances

in their favor, and to advance upon the ground occupied by their

neighbors and opponents.

The proximity of distinct climates produced by the inequalities of the

earth's surface, brings species possessing very different constitutions

into such immediate contact, that their naturalizations are very speedy

whenever opportunities of advancing present themselves. Many insects and

plants, for example, are common to low plains within the arctic circle,

and to lofty mountains in Scotland and other parts of Europe. If the

climate, therefore, of the polar regions were transferred to our own

latitudes, the species in question would immediately descend from these

elevated stations to overrun the low grounds. Invasions of this kind,

attended by the expulsion of the pre-occupants, are almost

instantaneous, because the change of temperature not only places the one

species in a more favorable position, but renders the others sickly and

almost incapable of defence.

_These changes inconsistent with the theory of transmutation._--Lamarck,

when speculating on the transmutation of species, supposed every

modification in organization and instinct to be brought about slowly and

insensibly in an indefinite lapse of ages. But he does not appear to

have sufficiently considered how much every alteration in the physical

condition of the habitable surface changes the relations of a great

number of coexisting species, and that some of these would be ready

instantly to avail themselves of the slightest change in their favor,

and to multiply to the injury of others. Even if we thought it possible

that the palm or the elephant, which now flourish in equatorial regions,

could ever learn to bear the variable seasons of our temperate zone, or

the rigors of an arctic winter, we might with no less confidence affirm,

that they must perish before they had time to become habituated to such

new circumstances. That they would be displaced by other species as

often as the climate varied, may be inferred from the data before

explained respecting the local extermination of species produced by the

multiplication of others.

Suppose the climate of the highest part of the woody zone of Etna to be

transferred to the sea-shore of the base of the mountain, no botanist

would anticipate that the olive, lemon-tree, and prickly pear (_Cactus

Opuntia_) would be able to contend with the oak and chestnut, which

would begin forthwith to descend to a lower level; or that these last

would be able to stand their ground against the pine, which would also,

in the space of a few years, begin to occupy a lower position. We might

form some kind of estimate of the time which might be required for the

migrations of these plants; whereas we have no data for concluding that

any number of thousands of years would be sufficient for one step in

the pretended metamorphosis of one species into another, possessing

distinct attributes and qualities.

This argument is applicable not merely to _climate_, but to any other

cause of mutation. However slowly a lake may be converted into a marsh,

or a marsh into a meadow, it is evident that before the lacustrine

plants can acquire the power of living in marshes, or the marsh-plants

of living in a less humid soil, other species, already existing in the

region, and fitted for these several stations, will intrude and keep

possession of the ground. So, if a tract of salt water becomes fresh by

passing through every intermediate degree of brackishness, still the

marine mollusks will never be permitted to be gradually metamorphosed

into fluviatile species; because long before any such transformation can

take place by slow and insensible degrees, other tribes, already formed

to delight in brackish or fresh water, will avail themselves of the

change in the fluid, and will, each in their turn, monopolize the space.

It is idle, therefore, to dispute about the abstract possibility of the

conversion of one species into another, when there are known causes so

much more active in their nature, which must always intervene and

prevent the actual accomplishment of such conversions. A faint image of

the certain doom of a species less fitted to struggle with some new

condition in a region which it previously inhabited, and where it has to

contend with a more vigorous species, is presented by the extirpation of

savage tribes of men by the advancing colony of some civilized nation.

In this case the contest is merely between two different _races_--two

varieties, moreover, of a species which exceeds all others in its

aptitude to accommodate its habits to the most extraordinary variations

of circumstances. Yet few future events are more certain than the speedy

extermination of the Indians of North America and the savages of New

Holland in the course of a few centuries, when these tribes will be

remembered only in poetry or history.

_Concluding remarks._--We often hear astonishment expressed at the

disappearance from the earth in times comparatively modern of many small

as well as large animals, the remains of which have been found in a

fossil state, under circumstances implying that neither any great

geographical revolution, nor the exterminating influence of man has

intervened to account for their extinction. But in all such cases we

should inquire whether we are sufficiently acquainted with the numerous

and complicated conditions on which the perpetuation of each species

depends, to entitle us to wonder if it should be suddenly cut off.

Mr. Darwin, when calling attention to the fact that the horse,

megatherium, megalonyx, and many contemporary Mammalia, had perished in

South America after that continent had acquired its present

configuration, and when, if we may judge by the Testacea, the climate

very nearly resembled the present, observes, "that in the living

creation one species is often extremely rare in a given region, while

another of the same genus and with closely allied habits is exceedingly

common. A zoologist familiar with such phenomena, if asked to explain

them, usually replies, that some slight difference in climate, food, or

the number of its enemies, must determine the relative strength of the

two species in question, although we may be unable to point out the

precise manner of the action of the check. We are, therefore, driven to

the conclusion, that causes generally quite inappreciable by us

determine whether a given species shall be abundant or scanty in

numbers. Why, then, should we feel astonishment if the rarity is

occasionally carried a step farther,--to extinction?"[989]

CHAPTER XLIII.

EXTINCTION AND CREATION OF SPECIES.

Theory of the successive extinction of species consistent with a

limited geographical distribution--Opinions of botanists respecting

the centres from which plants have been diffused--Whether there are

grounds for inferring that the loss, from time to time, of certain

animals and plants, is compensated by the introduction of new

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

expected within the historical era?--The question whether the

existing species have been created in succession must be decided by

geological monuments.

_Successive Extinction of Species consistent with their limited

Geographical Distribution._

In the preceding chapters I have pointed out the strict dependence of

each species of animal and plant on certain physical conditions in the

state of the earth's surface, and on the number and attributes of other

organic beings inhabiting the same region. I have also endeavored to

show that all these conditions are in a state of continual fluctuation,

the igneous and aqueous agents remodelling, from time to time, the

physical geography of the globe, and the migrations of species causing

new relations to spring up successively between different organic

beings. I have deduced as a corollary, that the species existing at any

particular period, must, in the course of ages, become extinct one after

the other. "They must die out," to borrow an emphatical expression from

Buffon, "because Time fights against them."

If the views which I have taken are just, there will be no difficulty in

explaining why the habitations of so many species are now restrained

within exceedingly narrow limits. Every local revolution, such as those

contemplated in the preceding chapter, tends to circumscribe the range

of some species, while it enlarges that of others; and if we are led to

infer that new species originate in one spot only, each must require

time to diffuse itself over a wide area. It will follow, therefore, from

the adoption of this hypothesis, that the recent origin of some species,

and the high antiquity of others, are equally consistent with the

general fact of their limited distribution; some being local, because

they have not existed long enough to admit of their wide dissemination;

others, because circumstances in the animate or inanimate world have

occurred to restrict the range which they may once have obtained. As a

general rule, however, species, common to many distant provinces, or

those now found to inhabit very distant parts of the globe, are to be

regarded as the most ancient. Numerically speaking, they may not perhaps

be largely represented, but their wide diffusion shows that they have

had a long time to spread themselves, and have been able to survive many

important revolutions in physical geography.

After so much evidence has been brought to light by the geologist, of

land and sea having changed places in various regions since the existing

species were in being, we can feel no surprise that the zoologist and

botanist have hitherto found it difficult to refer the geographical

distribution of species to any clear and determinate principles, since

they have usually speculated on the phenomena, upon the assumption that

the physical geography of the globe had undergone no material alteration

since the introduction of the species now living. So long as this

assumption was made, the facts relating to the geography of plants and

animals appeared capricious in the extreme, and by many the subject was

pronounced to be so full of mystery and anomalies, that the

establishment of a satisfactory theory was hopeless.[990]

_Centres from which plants have been diffused._--Some botanists

conceived, in accordance with the hypothesis of Wildenow, that mountains

were the centres of creation from which the plants now inhabiting large

continents have radiated; to which De Candolle and others, with much

reason, objected, that mountains, on the contrary, are often the

barriers between two provinces of distinct vegetation. The geologist who

is acquainted with the extensive modifications which the surface of the

earth has undergone in very recent geological epochs, may be able,

perhaps, to reconcile both these theories in their application to

different regions.

A lofty range of mountains, which is so ancient as to date from a period

when the species of animals and plants differed from those now living,

will naturally form a barrier between contiguous provinces; but a chain

which has been raised, in great part, within the epoch of existing

species, and around which new lands have arisen from the sea within that

period, will be a centre of peculiar vegetation.

"In France," observes De Candolle, "the Alps and Cevennes prevent a

great number of the plants of the south from spreading themselves to the

northward; but it has been remarked that some species have made their

way through the gorges of these chains, and are found on their northern

sides, principally in those places where they are lower and more

interrupted."[991] Now the chains here alluded to have probably been of

considerable height ever since the era when the existing vegetation

began to appear, and were it not for the deep fissures which divide

them, they might have caused much more abrupt terminations to the

extension of distinct assemblages of species.

Parts of the Italian peninsula, on the other hand, have gained a

considerable portion of their present height since a majority of the

marine species now inhabiting the Mediterranean, and probably, also,

since the terrestrial plants of the same region were in being. Large

tracts of land have been added, both on the Adriatic and Mediterranean

side, to what originally constituted a much narrower range of mountains,

if not a chain of islands running nearly north and south, like Corsica

and Sardinia. It may therefore be presumed that the Apennines have been

a centre whence species have diffused themselves over the contiguous

_lower_ and _newer_ regions. In this and all analogous situations, the

doctrine of Wildenow, that species have radiated from the mountains as

from centres, may be well founded.

_Introduction of New Species._

If the reader should infer, from the facts laid before him in the

preceding chapters, that the successive extinction of animals and plants

may be part of the constant and regular course of nature, he will

naturally inquire whether there are any means provided for the repair of

these losses? Is it part of the economy of our system that the habitable

globe should, to a certain extent, become depopulated both in the ocean

and on the land; or that the variety of species should diminish until

some new era arrives when a new and extraordinary effort of creative

energy is to be displayed? Or is it possible that new species can be

called into being from time to time, and yet that so astonishing a

phenomenon can escape the observation of naturalists?

Humboldt has characterized these subjects as among the mysteries which

natural science cannot reach; and he observes that the investigation of

the origin of beings does not belong to zoological or botanical

geography. To geology, however, these topics do strictly appertain; and

this science is chiefly interested in inquiries into the state of the

animate creation as it now exists, with a view of pointing out its

relations to antecedent periods when its condition was different.

Before offering any hypothesis towards the solution of so difficult a

problem, let us consider what kind of evidence we ought to expect, in

the present state of science, of the first appearance of new animals or

plants, if we could imagine the successive creation of species to

constitute, like their gradual extinction, a regular part of the economy

of nature.

In the first place it is obviously more easy to prove that a species,

once numerously represented in a given district, has ceased to be, than

that some other which did not pre-exist has made its

appearance--assuming always, for reasons before stated, that single

stocks only of each animal and plant are originally created, and that

individuals of new species do not suddenly start up in many different

places at once.

So imperfect has the science of natural history remained down to our own

times, that, within the memory of persons now living, the numbers of

known animals and plants have been doubled, or even quadrupled, in many

classes. New and often conspicuous species are annually discovered in

parts of the old continent, long inhabited by the most civilized

nations. Conscious, therefore, of the limited extent of our information,

we always infer, when such discoveries are made, that the beings in

question had previously eluded our research; or had at least existed

elsewhere, and only migrated at a recent period into the territories

where we now find them. It is difficult, even in contemplation, to

anticipate the time when we shall be entitled to make any other

hypothesis in regard to all the marine tribes, and to by far the greater

number of the terrestrial;--such as birds, which possess such unlimited

powers of migration; insects, which, besides the variability of each

species in number, are also so capable of being diffused to vast

distances; and cryptogamous plants, to which, as to many other classes,

both of the animal and vegetable kingdom, similar observations are

applicable.

_What kind of evidence of new creations could be expected?_--What kind

of proofs, therefore, could we reasonably expect to find of the origin

at a particular period of a new species?

Perhaps it may be said in reply that, within the last two or three

centuries, some forest tree or new quadruped might have been observed to

appear suddenly in those parts, of England or France which had been most

thoroughly investigated;--that naturalists might have been able to show

that no such living being inhabited any other region of the globe, and

that there was no tradition of anything similar having before been

observed in the district where it had made its appearance.

Now, although this objection may seem plausible, yet its force will be

found to depend entirely on the rate of fluctuation which we suppose to

prevail in the animate world, and on the proportion which such

conspicuous subjects of the animal and vegetable kingdoms bear to those

which are less known and escape our observation. There are, perhaps,

more than a million species of plants and animals, exclusive of the

microscopic and infusory animalcules, now inhabiting the terraqueous

globe. The terrestrial plants may amount, says De Candolle, to somewhere

between 110,000 and 120,000;[992] but the data on which this conjecture

is founded are considered by many botanists to be vague and

unsatisfactory. Sprengel only enumerated, in 1827, about 31,000 known

phaenogamous, and 6000 cryptogamous plants; but that naturalist omitted

many, perhaps 7000 phaenogamous, and 1000 cryptogamous species. Mr.

Lindley, in a letter to the author in 1836, expressed his opinion that

it would be rash to speculate on the existence of more than 80,000

phaenogamous, and 10,000 cryptogamous plants. "If we take," he says, in a

letter to the author on this subject, "37,000 as the number of published

phaenogamous species, and then add, for the undiscovered species in Asia

and New Holland, 15,000, in Africa 10,000, and in America 18,000, we

have 80,000 species; and if 7000 be the number of published cryptogamous

plants, and we allow 3000 for the undiscovered species (making 10,000),

there would then be, on the whole, 90,000 species." But since that

period one catalogue, as I learn from Dr. J. Hooker, contains a list of

the names of 78,000 phaenogamous plants which had been published before

1841.

It was supposed by Linnaeus that there were four or five species of

insects in the world for each phaenogamous plant: but if we may judge

from the relative proportion of the two classes in Great Britain, the

number of insects must be still greater; for the total number of British

insects, "according to the last census," is about 12,500;[993] whereas

there are only 1500 phaenogamous plants indigenous to our island. As the

insects are much more numerous in hot countries than in our temperate

latitudes, it seems difficult to avoid the conclusion that there are

more than half a million species in the world.

The number of known mammifers, when Temminck wrote, exceeded 800, and

Mr. Waterhouse informs me that more than 1200 are now (1850) ascertained

to exist. Baron Cuvier estimated the amount of known fishes at 6000; and

Mr. G. Gray, in his "Genera of Birds," enumerates 8000 species. We have

still to add the reptiles, and all the invertebrated animals, exclusive

of insects. It remains, in a great degree, mere matter of conjecture

what proportion the aquatic tribes may bear to the denizens of the land;

but the habitable surface beneath the waters can hardly be estimated at

less than double that of the continents and islands, even admitting that

a very considerable area is destitute of life, in consequence of great

depth, cold, darkness, and other circumstances. In the late polar

expedition it was found that, in some regions, as in Baffin's Bay, there

were marine animals inhabiting the bottom at great depths, where the

temperature of the water was below the freezing point. That there is

life at much greater profundities in warmer regions may be confidently

inferred.

The ocean teems with life--the class of _Polyps_ alone are conjectured

by Lamarck to be as strong in individuals as insects. Every tropical

reef is described as covered with Corals and Sponges, and swarming with

Crustacea, Echini, and Testacea; while almost every tide-washed rock in

the world is carpeted with Fuci, and supports some Corallines, Actiniae,

and Mollusca. There are innumerable forms in the seas of the warmer

zones, which have scarcely begun to attract the attention of the

naturalist; and there are parasitic animals without number, three or

four of which are sometimes appropriated to one genus, as to the whale

(_Balaena_), for example. Even though we concede, therefore, that the

geographical range of marine species is more extensive in general than

that of the terrestrial (the temperature of the sea being more uniform,

and the land impeding less the migrations of the oceanic than the ocean

those of the terrestrial species), yet it seems probable that the

aquatic tribes far exceed in number the inhabitants of the land.

Without insisting on this point, it may be safe to assume, that,

exclusive of microscopic beings, there are between one and two millions

of species now inhabiting the terraqueous globe; so that if only one of

these were to become extinct annually, and one new one were to be every

year called into being, much more than a million of years might be

required to bring about a complete revolution in organic life.

I am not hazarding at present any hypothesis as to the probable rate of

change; but none will deny that when the _annual_ birth and the _annual_

death of one species on the globe is proposed as a mere speculation,

this at least is to imagine no slight degree of instability in the

animate creation. If we divide the surface of the earth into twenty

regions of equal area, one of these might comprehend a space of land and

water about equal in dimensions to Europe, and might contain a twentieth

part of the million of species which may be assumed to exist in the

animal kingdom. In this region one species only would, according to the

rate of mortality before assumed, perish in twenty years, or only five

out of fifty thousand in the course of a century. But as a considerable

proportion of the whole would belong to the aquatic classes, with which

we have a very imperfect acquaintance, we must exclude them from our

consideration; and if they constitute half of the entire number, then

one species only might be lost in forty years among the terrestrial

tribes. Now the Mammalia, whether terrestrial or aquatic, bear so small

a proportion to other classes of animals, forming less, perhaps, than

one thousandth part of the whole, that if the longevity of species in

the different orders were equal, a vast period must elapse before it

would come to the turn of this conspicuous class to lose one of their

number. If one species only of the whole animal kingdom died out in

forty years, no more than one mammifer might disappear in 40,000 years

in a region of the dimensions of Europe.

It is easy, therefore, to see, that in a small portion of such an area,

in countries, for example, of the size of England and France, periods

of much greater duration must elapse before it would be possible to

authenticate the first appearance of one of the larger plants and

animals, assuming the annual birth and death of one species to be the

rate of vicissitude in the animate creation throughout the world.

The observations of naturalists upon living species may, in the course

of future centuries, accumulate positive data, from which an insight

into the laws which govern this part of our terrestrial system may be

derived; but, in the present deficiency of historical records, we have

traced up the subject to that point where geological monuments alone are

capable of leading us on to the discovery of ulterior truths. To these,

therefore, we must appeal, carefully examining the strata of recent

formation wherein the remains of _living_ species, both animal and

vegetable, are known to occur. We must study these strata in strict

reference to their chronological order, as deduced from their

superposition, and other relations. From these sources we may learn

which of the species, now our contemporaries, have survived the greatest

revolutions of the earth's surface; which of them have co-existed with

the greatest number of animals and plants now extinct; and which have

made their appearance only when the animate world had nearly attained

its present condition.

From such data we may be enabled to infer, whether species have been

called into existence in succession, or all at one period; whether

singly, or by groups simultaneously; whether the antiquity of man be as

high as that of any of the inferior beings which now share the planet

with him, or whether the human species is one of the most recent of the

whole.

To some of these questions we can even now return a satisfactory answer;

and with regard to the rest, we have some data to guide conjecture, and

to enable us to speculate with advantage: but in order to be fully

qualified to enter upon such discussions the reader must study the ample

body of materials amassed by the industry of modern geologists.

CHAPTER XLIV.

EFFECTS PRODUCED BY THE POWERS OF VITALITY ON THE STATE OF THE EARTH'S

SURFACE.

Modifications in physical geography caused by organic beings--Why

the vegetable soil does not augment in thickness--The theory, that

vegetation is an antagonist power counterbalancing the degradation

caused by running water untenable--Conservative influence of

vegetation--Rain diminished by felling of forests--Distribution of

American forests dependent on direction of predominant

winds--Influence of man in modifying the physical geography of the

globe.

The second branch of our inquiry, respecting changes of the organic

world, relates to the processes by which the remains of animals and

plants become fossil, or, to speak still more generally, to all the

effects produced by the powers of vitality on the surface and shell of

the earth.

Before entering on the principal division of this subject, the imbedding

and preservation of animal and vegetable remains, I shall offer a few

remarks on the superficial modifications caused directly by the agency

of organic beings, as when the growth of certain plants covers the slope

of a mountain with peat, or converts a swamp into dry land; or when

vegetation prevents the soil, in certain localities, from being washed

away by running water.

In considering alterations of this kind, brought about in the physical

geography of particular tracts, we are too apt to think exclusively of

that part of the earth's surface which has emerged from beneath the

waters, and with which alone, as terrestrial beings, we are familiar.

Here the direct power of animals and plants to cause any important

variation is, of necessity, very limited, except in checking the

progress of that decay of which the land is the chief theatre. But if we

extend our views, and instead of contemplating the dry land, consider

that larger portion which is assigned to the aquatic tribes, we discover

the great influence of the living creation, in imparting varieties of

conformation to the solid exterior which the agency of inanimate causes

alone could not produce.

Thus, when timber is floated into the sea, it is often drifted to vast

distances, and subsides in spots where there might have been no deposit,

at that time and place, if the earth had not been tenanted by living

beings. If, therefore, in the course of ages, a hill of wood, or

lignite, be thus formed in the subaqueous regions, a change in the

submarine geography may be said to have resulted from the action of

organic powers. So in regard to the growth of coral reefs; it is

probable that a large portion of the matter of which they are composed

is supplied by mineral springs, which often rise up at the bottom of the

sea, and which, on land, abound throughout volcanic regions hundreds of

leagues in extent. The matter thus constantly given out could not go on

accumulating for ever in the waters, but would be precipitated in the

abysses of the sea, even if there were no polyps and testacea; but these

animals arrest and secrete the carbonate of lime on the summits of

submarine mountains, and form reefs many hundred feet in thickness, and

hundreds of miles in length, where, but for them, none might ever have

existed.

_Why the vegetable soil does not augment in thickness._--If no such

voluminous masses are formed on the land, it is not from the want of

solid matter in the structure of terrestrial animals and plants; but

merely because, as I have so often stated, the continents are those

parts of the globe where accessions of matter can scarcely ever take

place--where, on the contrary, the most solid parts already formed are,

each in their turn, exposed to gradual degradation. The quantity of

timber and vegetable matter which grows in a tropical forest in the

course of a century is enormous, and multitudes of animal skeletons are

scattered there during the same period, besides innumerable land shells

and other organic substances. The aggregate of these materials,

therefore, might constitute a mass greater in volume than that which is

produced in any coral-reef during the same lapse of years; but, although

this process should continue on the land for ever, no mountains of wood

or bone would be seen stretching far and wide over the country, or

pushing out bold promontories into the sea. The whole solid mass is

either devoured by animals, or decomposes, as does a portion of the rock

and soil on which the animals and plants are supported.

The waste of the strata themselves, accompanied by the decomposition of

their organic remains, and the setting free of their alkaline

ingredients, is one source from whence running water and the atmosphere

may derive the materials which are absorbed by the roots and leaves of

plants. Another source is the passage into a gaseous form of even the

hardest parts of animals and plants which die and putrefy in the air,

where they are soon resolved into the elements of which they are

composed: and while a portion of these constituents is volatilized, the

rest is taken up by rain-water, and sinks into the earth, or flows

towards the sea; so that they enter again and again into the composition

of different organic beings.

The principal elements found in plants are hydrogen, carbon, and oxygen;

so that water and the atmosphere contain all of them, either in their

own composition or in solution.[994] The constant supply of these

elements is maintained not only by the putrefaction of animal and

vegetable substances, and the decay of rocks, but also by the copious

evolution of carbonic acid and other gases from volcanoes and mineral

springs, and by the effects of ordinary evaporation, whereby aqueous

vapors are made to rise from the ocean, and to circulate round the

globe.

It is well known, that when two gases of different specific gravity are

brought into contact, even though the heavier be the lowermost, they

soon become uniformly diffused by mutual absorption through the whole

space which they occupy. By virtue of this law, the heavy carbonic acid

finds its way upwards through the lighter air of the atmosphere, and

conveys nourishment to the lichen which covers the mountain top.

If the quantity of food consumed by terrestrial animals, and the

elements imbibed by the roots and leaves of plants, were derived

entirely from that supply of hydrogen, carbon, oxygen, nitrogen, and

other elements, given out into the atmosphere and the waters by the

putrescence of organic substances, then we might imagine that the

vegetable mould would, after a series of years, neither gain nor lose a

single particle by the action of organic beings; and this conclusion is

not far from the truth; but the operation which renovates the vegetable

and animal mould is by no means so simple as that here supposed.

Thousands of carcases of terrestrial animals are floated down, every

century, into the sea; and, together with forests of drift-timber, are

imbedded in subaqueous deposits, where their elements are imprisoned in

solid strata, and may there remain locked up throughout whole geological

epochs before they again become subservient to the purposes of life.

On the other hand, fresh supplies are derived by the atmosphere and by

running water, as before stated, from the disintegration of rocks and

their organic contents, and through the agency of mineral springs from

the interior of the earth, from whence all the elements before

mentioned, which enter principally into the composition of animals and

vegetables, are continually evolved. Even nitrogen is found, by

chemists, to be contained very generally in the waters of mineral

springs.

_Vegetation not an antagonist power counterbalancing the action of

running water._--If we suppose that the copious supply from the nether

regions, by springs and volcanic vents, of carbonic acid and other

gases, together with the decomposition of rocks, may be just sufficient

to counterbalance that loss of matter which, having already served for

the nourishment of animals and plants, is annually carried down in

organized forms, and buried in subaqueous strata, we concede the utmost

that is consistent with probability. An opinion, however, has been

expressed, that the processes of vegetable life, by absorbing various

gases from the atmosphere, cause so large a mass of solid matter to

accumulate on the surface of the land, that this mass alone may

constitute a great counterpoise to all the matter transported to lower

levels by the aqueous agents of decay. "Torrents and rivers," it is

said--"the waves of the sea and marine currents--act upon lines only;

but the power of vegetation to absorb the elastic and non-elastic fluids

circulating round the earth, extends over the whole surface of the

continents. By the silent but universal action of this great antagonist

power, the spoliation and waste caused by running water on the land,

and by the movements of the ocean, are neutralized, and even

counterbalanced."[995]

In opposition to these views, I conceive that we shall form a juster

estimate of the influence of vegetation, if we consider it as being in a

slight degree conservative, and capable of retarding the waste of land,

but not of acting as an antagonist power. The vegetable mould is seldom

more than a few feet in thickness, and frequently does not exceed a few

inches; and we by no means find that its volume is more considerable on

those parts of our continents which we can prove, by geological data, to

have been elevated at more ancient periods, and where, consequently,

there has been the greatest time for the accumulation of vegetable

matter, produced throughout successive zoological epochs. On the

contrary, these higher and older regions are more frequently denuded, so

as to expose the bare rock to the action of the sun and air.

We find in the torrid zone, where the growth of plants is most rank and

luxurious, that accessions of matter due to their agency are by no means

the most conspicuous. Indeed it is in these latitudes, where the

vegetation is most active, that, for reasons to be explained in the next

chapter, even those superficial peat mosses are unknown which cover a

large area in some parts of our temperate zone. If the operation of

animal and vegetable life could restore to the general surface of the

continents a portion of the elements of those disintegrated rocks of

which such enormous masses are swept down annually into the sea, the

effects would long ere this have constituted one of the most striking

features in the structure and composition of our continents. All the

great steppes and table-lands of the world, where the action of running

water is feeble, would have become the grand repositories of organic

matter, accumulated without that intermixture of earthy sediment which

so generally characterizes the subaqueous strata.

I have already stated that, in the known operation of the _igneous_

causes, a real antagonist power is found, which may counterbalance the

levelling action of running water (p. 563); and there seems no good

reason for presuming that the upheaving and depressing force of

earthquakes, together with the ejection of matter by volcanoes, may not

be fully adequate to restore that inequality of the surface which rivers

and the waves and currents of the ocean annually tend to lessen. If a

counterpoise be derived from this source, the quantity and elevation of

land above the sea may for ever remain the same, in spite of the action

of the aqueous causes, which, if thus counteracted, may never be able to

reduce the surface of the earth more nearly to a state of equilibrium

than that which it has now attained; and, on the other hand, the force

of the aqueous agents themselves might thus continue for ever

unimpaired.

_Conservative influence of vegetation._--If, then, vegetation cannot act

as an antagonist power amid the mighty agents of change which are always

modifying the surface of the globe, let us next inquire how far its

influence is conservative,--how far it may retard the levelling effects

of running water, which it cannot oppose, much less counterbalance.

It is well known that a covering of herbage and shrubs may protect a

loose soil from being carried away by rain, or even by the ordinary

action of a river, and may prevent hills of loose sand from being blown

away by the wind; for the roots bind together the separate particles

into a firm mass, and the leaves intercept the rain-water, so that it

dries up gradually, instead of flowing off in a mass and with great

velocity. The old Italian hydrographers make frequent mention of the

increased degradation which has followed the clearing away of natural

woods in several parts of Italy. A remarkable example was afforded in

the Upper Val d' Arno, in Tuscany, on the removal of the woods clothing

the steep declivities of the hills by which that valley is bounded. When

the ancient forest laws were abolished by the Grand Duke Joseph, during

the last century, a considerable tract of surface in the Cassentina (the

Clausentinium of the Romans) was denuded, and immediately the quantity

of sand and soil washed down into the Arno increased enormously. Frisi,

alluding to such occurrences, observes, that as soon as the bushes and

plants were removed, the waters flowed off more rapidly, and, in the

manner of floods, swept away the vegetable soil.[996]

This effect of vegetation is of high interest to the geologist, when he

is considering the formation of those valleys which have been

principally due to the action of rivers. The spaces intervening between

valleys, whether they be flat or ridgy, when covered with vegetation,

may scarcely undergo the slightest waste, as the surface may be

protected by the green sward of grass; and this may be renewed, in the

manner before described, from elements derived from rain-water and the

atmosphere. Hence, while the river is continually bearing down matter in

the alluvial plain, and undermining the cliffs on each side of every

valley, the height of the intervening rising grounds may remain

stationary.

In this manner, a cone of loose scoriae, sand, and ashes, such as Monte

Nuovo, may, when it has once become densely clothed with herbage and

shrubs, suffer scarcely any further dilapidation; and the perfect state

of the cones of hundreds of extinct volcanoes in France, the Neapolitan

territory, Sicily, and elsewhere, may prove nothing whatever, either as

to their relative or absolute antiquity. We may be enabled to infer,

from the integrity of such conical hills of incoherent materials, that

no flood can have passed over the countries where they are situated,

since their formation; but the atmospheric action alone, in spots where

there happen to be no torrents, and where the surface was clothed with

vegetation, could scarcely in any lapse of ages have destroyed them.

During a tour in Spain, in 1830, I was surprised to see a district of

gently undulating ground in Catalonia, consisting of red and gray

sandstone, and in some parts of red marl, almost entirely denuded of

herbage; while the roots of the pines, holm oaks, and some other trees,

were half exposed, as if the soil had been washed away by a flood. Such

is the state of the forests, for example, between Oristo and Vich, and

near San Lorenzo. But, being overtaken by a violent thunder-storm, in

the month of August, I saw the whole surface, even the highest levels of

some flat-topped hills, streaming with mud, while on every declivity the

devastation of torrents was terrific. The peculiarities in the

physiognomy of the district were at once explained; and I was taught

that, in speculating on the greater effects which the direct action of

rain may once have produced on the surface of certain parts of England,

we need not revert to periods when the heat of the climate was

_tropical_.

In the torrid zone the degradation of land is generally more rapid; but

the waste is by no means proportioned to the superior quantity of rain

or the suddenness of its fall, the transporting power of water being

counteracted by a greater luxuriance of vegetation. A geologist who is

no stranger to tropical countries observes, that the softer rocks would

speedily be washed away in such regions, if the numerous roots of plants

were not matted together in such a manner as to produce considerable

resistance to the destructive power of the rains. The parasitical and

creeping plants also entwine in every possible direction, so as to

render the forests nearly impervious, and the trees possess forms and

leaves best calculated to shoot off the heavy rains; which, when they

have thus been broken in their fall, are quickly absorbed by the ground

beneath, or, when thrown into the drainage depressions, give rise to

furious torrents.[997]

_Influence of Man in modifying the Physical Geography of the Globe._

Before concluding this chapter, I shall offer a few observations on the

influence of man in modifying the physical geography of the globe; for

we must class his agency among the powers of organic nature.

_Felling of forests._--The felling of forests has been attended, in many

countries, by a diminution of rain, as in Barbadoes and Jamaica.[998]

For in tropical countries, where the quantity of aqueous vapor in the

atmosphere is great, but where, on the other hand, the direct rays of

the sun are most powerful, any impediment to the free circulation of

air, or any screen which shades the earth from the solar rays, becomes a

source of humidity; and wherever dampness and cold have begun to be

generated by such causes, the condensation of vapor continues. The

leaves, moreover, of all plants are alembics, and some of those in the

torrid zone have the remarkable property of distilling water, thus

contributing to prevent the earth from becoming parched up.

_Distribution of the American forests._--There can be no doubt then,

that the state of the climate, especially the humidity of the

atmosphere, influences vegetation, and that, in its turn, vegetation

re-acts upon the climate: but some writers seem to have attributed too

much importance to the influence of forests, particularly those of

America, as if they were the primary cause of the moisture of the

climate.

The theory of a modern author on this subject "that forests exist in

those parts of America only where the predominant winds carry with them

a considerable quantity of moisture from the ocean," seems far more

rational. In all countries, he says, "having a summer heat exceeding

70 degrees, the presence or absence of natural woods, and their greater

or less luxuriance, may be taken as a measure of the amount of humidity,

and of the fertility of the soil. Short and heavy rains in a warm

country will produce grass, which, having its roots near to the surface,

springs up in a few days, and withers when the moisture is exhausted;

but transitory rains, however heavy, will not nourish trees; because,

after the surface is saturated, the remainder of the water runs off, and

the moisture lodged in the soil neither sinks deep enough, nor is in

sufficient quantity, to furnish the giants of the forests with the

necessary sustenance. It may be assumed that twenty inches of rain

falling moderately or at intervals, will leave a greater permanent

supply in the soil than forty inches falling, as it sometimes does in

the torrid zone, in as many hours."[999]

"In all regions," he continues, "where ranges of mountains intercept the

course of the constant or predominant winds, the country on the windward

side of the mountains will be moist, and that on the leeward dry; and

hence parched deserts will generally be found on the west side of

countries within the tropics, and on the east side of those beyond them,

the prevailing winds in these cases being generally in opposite

directions. On this principle, the position of forests in North and

South America may be explained. Thus, for example, in the region within

the thirtieth parallel, the moisture swept up by the trade-wind from the

Atlantic is precipitated in part upon the mountains of Brazil, which are

but low, and so distributed as to extend far into the interior. The

portion which remains is borne westward, and, losing a little as it

proceeds, is at length arrested by the Andes, where it falls down in

showers on their summits. The aarial current, now deprived of all the

humidity with which it can part, arrives in a state of complete

exsiccation at Peru, where consequently no rain falls. But in the region

of America, beyond the thirtieth parallel, the Andes serve as a screen

to intercept the moisture brought by the prevailing winds from the

Pacific Ocean: rains are copious on their summits, and in Chili on their

_western_ declivities; but none falls on the plains to the _eastward_,

except occasionally when the wind blows from the Atlantic."[1000]

I have been more particular in explaining these views, because they

appear to place in a true light the dependence of vegetation on climate,

the humidity being increased, and more uniformly diffused throughout the

year, by the gradual spreading of wood.

It has been affirmed, that formerly, when France and England were

covered with wood, Europe was much colder than at present; that the

winters in Italy were longer, and that the Seine, and many other rivers,

froze more regularly every winter than now. M. Arago, in an essay on

this subject, has endeavored to show, by tables of observations on the

congelation of the Rhine, Danube, Rhone, Po, Seine, and other rivers, at

different periods, that there is no reason to believe the cold to have

been in general more intense in ancient times.[1001] He admits, however,

that the climate of Tuscany has been so far modified, by the removal of

wood, as that the winters are less cold; but the summers also, he

contends, are less hot than of old; and the summers, according to him,

were formerly hotter in France than in our own times. His evidence is

derived chiefly from documents showing that wine was made three

centuries ago in the Vivarais and several other provinces, at an earlier

season, at greater elevations, and in higher latitudes, than are now

found suitable to the vine.

There seems little doubt that in the United States of North America the

rapid _clearing_ of the country has rendered the winters less severe and

the summers less hot; in other words, the extreme temperatures of

January and July have been observed from year to year to approach

somewhat nearer to each other. Whether in this case, or in France, the

_mean_ temperature has been raised, seems by no means as yet decided;

but there is no doubt that the climate has become, as Buffon would have

said, "less excessive."

I have before shown, when treating of the excavation of new estuaries in

Holland by inroads of the ocean, as also of the changes on our own

coasts, that although the conversion of sea into land by artificial

labors may be great, yet it must always be in subordination to the power

of the tides and currents, or to the great movements which alter the

relative level of the land and sea, (Chap. XX.) If, in addition to the

assistance obtained by parliamentary grants for defending Dunwich from

the waves, all the resources of Europe had been directed to the same

end, the existence of that port might perhaps have been prolonged for

several centuries (p. 310.) But in the mean time, the current would have

continued to sweep away portions from the adjoining cliffs on each side,

giving to the whole line of coast its present form, until at length the

town, projecting as a narrow promontory, must have become exposed to the

irresistible fury of the waves.

It is scarcely necessary to observe, that the control which man can

obtain over the igneous agents is less even than that which he may exert

over the aqueous. He cannot modify the upheaving or depressing force of

earthquakes, or the periods or degree of violence of volcanic eruptions;

and on these causes the inequalities of the earth's surface, and,

consequently, the shape of the sea and land, appear mainly to depend.

The utmost that man can hope to effect in this respect is occasionally

to divert the course of a lava-stream, and to prevent the burning

matter, for a season, from overwhelming a city, or some other of the

proudest works of human industry.

If all the nations of the earth should attempt to quarry away the lava

which flowed during one eruption from the Icelandic volcanoes in 1783,

and the two following years, and should attempt to consign it to the

deepest abysses of the ocean, they might toil for thousands of years and

not accomplish their task. Yet the matter borne down to the sea by two

great rivers, the Ganges and Burrampooter, in each quarter of a century,

probably equals in weight and volume the mass of Icelandic lava produced

by that great eruption (p. 282). So insignificant is the aggregate force

exerted by man, when contrasted with the ordinary operations of aqueous

or igneous agents in the natural world.

No application, perhaps, of human skill and labor tends so greatly to

vary the state of the habitable surface, as that employed in the

drainage of lakes and marshes, since not only the _stations_ of many

animals and plants, but the general climate of a district, may thus be

modified. It is also a kind of alteration to which it is difficult to

find anything analogous in the agency of inferior beings; for we ought

always, before we decide that any part of the influence of man is novel

and anomalous, carefully to consider the powers of all other animated

agents which may be limited or superseded by him.[1002] Many who have

reasoned on these subjects seem to have forgotten that the human race

often succeeds to the discharge of functions previously fulfilled by

other species. Suppose the growth of some of the larger terrestrial

plants, or, in other words, the extent of forest, to be diminished by

man, and the climate to be thereby modified, it does not follow that

this kind of innovation is unprecedented. It is a change in the state of

vegetation, and such may often have been the result of the appearance of

new species upon the earth. The multiplication, for example, of certain

insects in parts of Germany, during the last century, destroyed more

trees than man, perhaps, could have felled during an equal period.

It would be rash, however, to affirm that the power of man to modify the

surface may not differ in kind or degree from that of other living

beings; although the problem is certainly more complex than many who

have speculated on such topics have imagined. If land be raised from the

sea, the greatest alteration in its physical condition, which could ever

arise from the influence of organic beings, would probably be produced

by the first immigration of terrestrial plants, whereby the new tract

would become covered with vegetation. The change next in importance

would seem to be when animals first enter, and modify the proportionate

numbers of certain species of plants. If there be any anomaly in the

intervention of man, in farther varying the relative numbers in the

vegetable kingdom, it may not so much consist in the kind or absolute

quantity of alteration, as in the circumstance that a _single species_,

in this case, would exert, by its superior power and universal

distribution, an influence equal to that of hundreds of other

terrestrial animals.

If we inquire whether man, by his direct power, or by the changes which

he may give rise to indirectly, tends, upon the whole, to lessen or

increase the inequalities of the earth's surface, we shall incline,

perhaps, to the opinion that he is a levelling agent. In mining

operations he conveys upwards a certain quantity of materials from the

bowels of the earth; but, on the other hand, much rock is taken annually

from the land, in the shape of ballast, and afterwards thrown into the

sea, and by this means, in spite of prohibitory laws, many harbors, in

various parts of the world, have been blocked up. We rarely transport

heavy materials to higher levels, and our pyramids and cities are

chiefly constructed of stone brought down from more elevated situations.

By ploughing up thousands of square miles, and exposing a surface for

part of the year to the action of the elements, we assist the abrading

force of rain, and diminish the conservative effects of vegetation.

CHAPTER XLV.

INCLOSING OF FOSSILS IN PEAT, BROWN SAND, AND VOLCANIC EJECTIONS.

Division of the subject--Imbedding of organic remains in deposits on

emerged land--Growth of peat--Site of ancient forests in Europe now

occupied by peat--Bog iron-ore--Preservation of animal substances in

peat--Miring of quadrupeds--Bursting of the Solway moss--Great

Dismal Swamp--Imbedding of organic bodies and human remains in blown

sand--Moving sands of African deserts--De Luc on their recent

origin--Buried temple of Ipsambul--Dried carcases in the

sands--Towns overwhelmed by sand-floods--Imbedding of organic and

other remains in volcanic formations on the land.

_Division of the subject._--The next subject of inquiry is the mode in

which the remains of animals and plants become fossil, or are buried in

the earth by natural causes. M. Constant Prevost has observed, that the

effects of geological causes are divisible into two great classes; those

produced during the submersion of land beneath the waters, and those

which take place after its emersion. Agreeably to this classification, I

shall consider, first, in what manner animal and vegetable remains

become included and preserved in deposits on emerged land, or that part

of the surface which is not _permanently_ covered by water, whether of

seas or lakes; secondly, the manner in which organic remains become

imbedded in subaqueous deposits.

Under the first division, I shall treat of the following topics:--1st,

the growth of peat, and the preservation of vegetable and animal remains

therein;--2dly, the burying of organic remains in blown sand;--3dly, of

the same in the ejections and alluviums of volcanoes;--4thly, in

alluviums generally, and in the ruins of landslips;--5thly, in the mud

and stalagmite of caves and fissures.

_Growth of Peat, and Preservation of Vegetable and Animal Remains

therein._

The generation of peat, when not completely under water, is confined to

moist situations, where the temperature is low, and where vegetables may

decompose without putrefying. It may consist of any of the numerous

plants which are capable of growing in such _stations_; but a species of

moss (_Sphagnum_) constitutes a considerable part of the peat found in

marshes of the north of Europe; this plant having the property of

throwing up new shoots in its upper part, while its lower extremities

are decaying.[1003] Reeds, rushes, and other aquatic plants may usually

be traced in peat; and their organization is often so entire that there

is no difficulty in discriminating the distinct species.

_Analysis of peat._--In general, says Sir H. Davy, one hundred parts of

dry peat contain from sixty to ninety-nine parts of matter destructible

by fire; and the residuum consists of earths usually of the same kind as

the substratum of clay, marl, gravel, or rock, on which they are found,

together with oxide of iron. "The peat of the chalk counties of

England," observes the same writer, "contains much gypsum: but I have

found very little in any specimens from Ireland or Scotland, and in

general these peats contain very little saline matter."[1004] From the

researches of Dr. MacCulloch, it appears that peat is intermediate

between simple vegetable matter and lignite, the conversion of peat to

lignite being gradual, and being brought about by a prolonged action of

water.[1005]

_Peat abundant in cold and humid climates._--Peat is sometimes formed on

a declivity in mountainous regions, where there is much moisture; but in

such situations it rarely, if ever, exceeds four feet in thickness. In

bogs, and in low grounds into which alluvial peat is drifted, it is

found forty feet thick, and upwards; but in such cases it generally owes

one half of its volume to the water which it contains. It has seldom, if

ever, been discovered within the tropics; and it rarely occurs in the

valleys, even in the south of France and Spain. It abounds more and

more, in proportion as we advance farther from the equator, and becomes

not only more frequent but more inflammable in northern latitudes.[1006]

The same phenomenon is repeated in the southern hemisphere. No peat is

found in Brazil, nor even in the swampy parts of the country drained by

the La Plata on the east side of South America, or in the island of

Chiloe on the west; yet when we reach the 45th degree of latitude and

examine the Chonos Archipelago or the Falkland Islands, and Tierra del

Fuego, we meet with an abundant growth of this substance. Almost all

plants contribute here by their decay to the production of peat, even

the grasses; but it is a singular fact, says Mr. Darwin, as contrasted

with what occurs in Europe, that no kind of moss enters into the

composition of the South American peat, which is formed by many plants,

but chiefly by that called by Brown _Astelia pumila_.[1007]

I learn from Dr. Forchhammer (1849) that water charged with vegetable

matter in solution does not throw down a deposit of peat in countries

where the mean temperature of the year is above 43 degrees or 44 degrees

Fahrenheit. Frost causes the precipitation of such peaty matter, but in

warm climates the attraction of the carbon for the oxygen of the air

mechanically mixed with the water increases with the increasing

temperature, and the dissolved vegetable matter or humic acid (which is

organic matter in a progressive state of decomposition) being converted

into carbonic acid, rises and is absorbed into the atmosphere, and thus

disappears.

_Extent of surface covered by peat._--There is a vast extent of surface

in Europe covered with peat, which, in Ireland, is said to extend over a

tenth of the whole island. One of the mosses on the Shannon is described

as being fifty miles long, by two or three broad; and the great marsh of

Montoire, near the mouth of the Loire, is mentioned, by Blavier, as

being more than fifty leagues in circumference. It is a curious and

well-ascertained fact, that many of these mosses of the north of Europe

occupy the place of forests of pine and oak, which have, many of them,

disappeared within the historical era. Such changes are brought about by

the fall of trees and the stagnation of water, caused by their trunks

and branches obstructing the free drainage of the atmospheric waters,

and giving rise to a marsh. In a warm climate, such decayed timber would

immediately be removed by insects, or by putrefaction; but, in the cold

temperature now prevailing in our latitudes, many examples are recorded

of marshes originating in this source. Thus, in Mar forest, in

Aberdeenshire, large trunks of Scotch fir, which had fallen from age and

decay, were soon immured in peat, formed partly out of their perishing

leaves and branches, and in part from the growth of other plants. We

also learn, that the overthrow of a forest by a storm, about the middle

of the seventeenth century, gave rise to a peat-moss near Lochbroom, in

Ross-shire, where, in less than half a century after the fall of the

trees, the inhabitants dug peat.[1008] Dr. Walker mentions a similar

change, when, in the year 1756, the whole wood of Drumlaurig in

Dumfries-shire was overset by the wind. Such events explain the

occurrence, both in Britain and on the Continent, of mosses where the

trees are all broken within two or three feet of the original surface,

and where their trunks all lie in the same direction.[1009]

It may however be suggested in these cases, that the soil had become

exhausted for trees, and that, on the principle of that natural rotation

which prevails in the vegetable world, one set of plants died out and

another succeeded. It is certainly a remarkable fact that in the Danish

islands, and in Jutland and Holstein, fir wood of various species,

especially Scotch fir, is found at the bottom of the peat-mosses,

although it is well ascertained that for the last five centuries no

Coniferae have grown wild in these countries; the coniferous trees which

now flourish there having been all planted towards the close of the last

century.

Nothing is more common than the occurrence of buried trees at the bottom

of the Irish peat-mosses, as also in most of those of England, France,

and Holland; and they have been so often observed with parts of their

trunks standing erect, and with their roots fixed to the subsoil, that

no doubt can be entertained of their having generally grown on the spot.

They consist, for the most part, of the fir, the oak, and the birch:

where the subsoil is clay, the remains of oak are the most abundant;

where sand is the substratum, fir prevails. In the marsh of Curragh, in

the Isle of Man, vast trees are discovered standing firm on their

roots, though at the depth of eighteen or twenty feet below the surface.

Some naturalists have desired to refer the imbedding of timber in

peat-mosses to aqueous transportation, since rivers are well known to

float wood into lakes; but the facts above mentioned show that, in

numerous instances, such an hypothesis is inadmissible. It has,

moreover, been observed, that in Scotland, as also in many parts of the

Continent, the largest trees are found in those peat-mosses which lie in

the least elevated regions, and that the trees are proportionally

smaller in those which lie at higher levels; from which fact De Luc and

Walker have both inferred that the trees grew on the spot, for they

would naturally attain a greater size in lower and warmer levels. The

leaves, also, and fruits of each species, are continually found immersed

in the moss along with the parent trees; as, for example, the leaves and

acorns of the oak, the cones and leaves of the fir, and the nuts of the

hazel.

_Recent origin of some peat-mosses._--In Hatfield moss, in Yorkshire,

which appears clearly to have been a forest eighteen hundred years ago,

fir-trees have been found ninety feet long, and sold for masts and keels

of ships; oaks have also been discovered there above one hundred feet

long. The dimensions of an oak from this moss are given in the

Philosophical Transactions, No. 275, which must have been larger than

any tree now existing in the British dominions.

In the same moss of Hatfield, as well as in that of Kincardine, in

Scotland, and several others, Roman roads have been found covered to the

depth of eight feet by peat. All the coins, axes, arms, and other

utensils found in British and French mosses, are also Roman; so that a

considerable portion of the peat in European peat-bogs is evidently not

more ancient than the age of Julius Caesar. Nor can any vestiges of the

ancient forests described by that general, along the line of the great

Roman way in Britain, be discovered, except in the ruined trunks of

trees in peat.

De Luc ascertained that the very sites of the aboriginal forests of

Hercinia, Semana, Ardennes, and several others, are now occupied by

mosses and fens; and a great part of these changes have, with much

probability, been attributed to the strict orders given by Severus, and

other emperors, to destroy all the wood in the conquered provinces.

Several of the British forests, however, which are now mosses, were cut

at different periods, by order of the English parliament, because they

harbored wolves or outlaws. Thus the Welsh woods were cut and burned, in

the reign of Edward I.; as were many of those in Ireland, by Henry II.,

to prevent the natives from harboring in them, and harassing his troops.

It is curious to reflect that considerable tracts have, by these

accidents, been permanently sterilized, and that, during a period when

civilization has been making great progress, large areas in Europe have,

by human agency, been rendered less capable of administering to the

wants of man. Rennie observes,[1010] with truth, that in those regions

alone which the Roman eagle never reached--in the remote circles of the

German empire, in Poland and Prussia, and still more in Norway, Sweden,

and the vast empire of Russia--can we see what Europe was before it

yielded to the power of Rome. Desolation now reigns where stately

forests of pine and oak once flourished, such as might now have supplied

all the navies of Europe with timber.

_Sources of bog iron-ore._--At the bottom of peat-mosses there is

sometimes found a cake, or "pan," as it is termed, of oxide of iron, and

the frequency of bog iron-ore is familiar to the mineralogist. The oak,

which is so often dyed black in peat, owes its color to the same metal.

From what source the iron is derived has often been a subject of

discussion, until the discoveries of Ehrenberg seem at length to have

removed the difficulty. He had observed in the marshes about Berlin a

substance of a deep ochre yellow passing into red, which covered the

bottom of the ditches, and which, where it had become dry after the

evaporation of the water, appeared exactly like oxide of iron. But under

the microscope it was found to consist of slender articulated threads or

plates, partly siliceous and partly ferruginous, of what he considered

an animalcule, _Gaillonella ferruginea_, but which most naturalists now

regard as a plant.[1011] There can be little doubt, therefore, that bog

iron-ore consists of an aggregate of millions of these organic bodies

invisible to the naked eye.[1012]

[Illustration: Fig. 101.

_Gaillonella ferruginea._

_a._ 2000 times magnified.]

_Preservation of animal substances in peat._--One interesting

circumstance attending the history of peat mosses is the high state of

preservation of animal substances buried in them for periods of many

years. In June, 1747, the body of a woman was found six feet deep, in a

peat-moor in the Isle of Axholm, in Lincolnshire. The antique sandals

on her feet afforded evidence of her having been buried there for many

ages: yet her nails, hair, and skin, are described as having shown

hardly any marks of decay. On the estate of the Earl of Moira, in

Ireland, a human body was dug up, a foot deep in gravel, covered with

eleven feet of moss; the body was completely clothed and the garments

seemed all to be made of hair. Before the use of wool was known in that

country the clothing of the inhabitants was made of hair, so that it

would appear that this body had been buried at that early period; yet it

was fresh and unimpaired.[1013] In the Philosophical Transactions we

find an example recorded of the bodies of two persons having been buried

in moist peat, in Derbyshire, in 1674, about a yard deep, which were

examined twenty-eight years and nine months afterwards; "the color of

their skin was fair and natural, their flesh soft as that of persons

newly dead."[1014]

Among other analogous facts we may mention, that in digging a pit for a

well near Dulverton, in Somersetshire, many pigs were found in various

postures, still entire. Their shape was well preserved, the skin, which

retained the hair, having assumed a dry, membranous appearance. Their

whole substance was converted into a white, friable, laminated,

inodorous, and tasteless substance; but which, when exposed to heat,

emitted an odor precisely similar to broiled bacon.[1015]

_Cause of the antiseptic property of peat._--We naturally ask whence

peat derives this antiseptic property? It has been attributed by some to

the carbonic and gallic acids which issue from decayed wood, as also to

the presence of charred wood in the lowest strata of many peat-mosses,

for charcoal is a powerful antiseptic, and capable of purifying water

already putrid. Vegetable gums and resins also may operate in the same

way.[1016]

The tannin occasionally present in peat is the produce, says Dr.

MacCulloch, of tormentilla, and some other plants; but the quantity he

thinks too small, and its occurrence too casual, to give rise to effects

of any importance. He hints that the soft parts of animal bodies,

preserved in peat-bogs, may have been converted into adipocire by the

action of water merely; an explanation which appears clearly applicable

to some of the cases above enumerated.[1017]

_Miring of quadrupeds._--The manner, however, in which peat contributes

to preserve, for indefinite periods, the harder parts of terrestrial

animals, is a subject of more immediate interest to the geologist. There

are two ways in which animals become occasionally buried in the peat of

marshy grounds; they either sink down into the semifluid mud, underlying

a turfy surface upon which they have rashly ventured, or, at other

times, as we shall see in the sequel, a bog "bursts," and animals may be

involved in the peaty alluvium.

In the extensive bogs of Newfoundland, cattle are sometimes found buried

with only their heads and necks above ground; and after having remained

for days in this situation, they have been drawn out by ropes and saved.

In Scotland, also, cattle venturing on the "quaking moss" are often

mired, or "laired," as it is termed; and in Ireland, Mr. King asserts

that the number of cattle which are lost in sloughs is quite

incredible.[1018]

_Solway moss._--The description given of the Solway moss will serve to

illustrate the general character of these boggy grounds. That moss,

observes Gilpin, is a flat area, about seven miles in circumference,

situated on the western confines of England and Scotland. Its surface is

covered with grass and rushes, presenting a dry crust and a fair

appearance; but it shakes under the least pressure, the bottom being

unsound and semifluid. The adventurous passenger, therefore, who

sometimes in dry seasons traverses this perilous waste, to save a few

miles, picks his cautious way over the rushy tussocks as they appear

before him, for here the soil is firmest. If his foot slip, or if he

venture to desert this mark of security, it is possible he may never

more be heard of.

"At the battle of Solway, in the time of Henry VIII. (1542), when the

Scotch army, commanded by Oliver Sinclair, was routed, an unfortunate

troop of horse, driven by their fears, plunged into this morass, which

instantly closed upon them. The tale was traditional, but it is now

authenticated; a man and horse, in complete armor, having been found by

peat-diggers, in the place where it was always supposed the affair had

happened. The skeleton of each was well preserved, and the different

parts of the armor easily distinguished."[1019]

The same moss, on the 16th of December, 1772, having been filled like a

great sponge with water during heavy rains, swelled to an unusual height

above the surrounding country, and then burst. The turfy covering seemed

for a time to act like the skin of a bladder retaining the fluid within,

till it forced a passage for itself, when a stream of black

half-consolidated mud began at first to creep over the plain,

resembling, in the rate of its progress, an ordinary lava-current. No

lives were lost, but the deluge totally overwhelmed some cottages, and

covered 400 acres. The highest parts of the original moss subsided to

the depth of about twenty-five feet; and the height of the moss, on the

lowest parts of the country which it invaded, was at least fifteen feet.

_Bursting of a peat-moss in Ireland._--A recent inundation in Sligo

(January, 1831), affords another example of this phenomenon. After a

sudden thaw of snow, the bog between Bloomfield and Geevah gave way; and

a black deluge, carrying with it the contents of a hundred acres of bog,

took the direction of a small stream and rolled on with the violence of

a torrent, sweeping along heath, timber, mud, and stones, and

overwhelming many meadows and arable land. On passing through some boggy

land, the flood swept out a wide and deep ravine, and part of the road

leading from Bloomfield to St. James's Well was completely carried away

from below the foundation for the breadth of 200 yards.

_Great Dismal Swamp._--I have described, in my Travels in North

America,[1020] an extensive swamp or morass, forty miles long from north

to south, and twenty-five wide, between the towns of Norfolk in

Virginia, and Weldon in North Carolina. It is called the "Great Dismal,"

and has somewhat the appearance of an inundated river-plain covered with

aquatic trees and shrubs, the soil being as black as that of a peat bog.

It is higher on all sides except one than the surrounding country,

towards which it sends forth streams of water to the north, east, and

south, receiving a supply from the west only. In its centre it rises 12

feet above the flat region which bounds it. The soil, to the depth of 15

feet, is formed of vegetable matter without any admixture, of earthy

particles, and offers an exception to a general rule before alluded to,

namely, that such peaty accumulations scarcely ever occur so far south

as lat. 36 degrees, or in any region where the summer heat is so great

as in Virginia. In digging canals through the morass for the purpose of

obtaining timber, much of the black soil has been thrown out from time

to time, and exposed to the sun and air, in which case it soon rots away

so that nothing remains behind, showing clearly that it owes its

preservation to the shade afforded by a luxuriant vegetation and to the

constant evaporation of the spongy soil by which the air is cooled

during the hot months. The surface of the bog is carpeted with mosses,

and densely covered with ferns and reeds, above which many evergreen

shrubs and trees flourish, especially the White Cedar (_Cupressus

thyoides_), which stands firmly supported by its long tap roots in the

softest parts of the quagmire. Over the whole the deciduous cypress

(_Taxodium distichum_) is seen to tower with its spreading top, in full

leaf in the season when the sun's rays are hottest, and when, if not

intercepted by a screen of foliage, they might soon cause the fallen

leaves and dead plants of the preceding autumn to decompose, instead of

adding their contributions to the peaty mass. On the surface of the wide

morass lie innumerable trunks of large and tall trees, while thousands

of others, blown down by the winds, are buried at various depths in the

black mire below. They remind the geologist of the prostrate position of

large stems of Sigillaria and Lepidodendron, converted into coal in

ancient carboniferous rocks.

_Bones of herbivorous quadrupeds in peat._--The antlers of large and

full-grown stags are amongst the most common and conspicuous remains of

animals in peat. They are not horns which have been shed; for portions

of the skull are found attached, proving that the whole animal perished.

Bones of the ox, hog, horse, sheep, and other herbivorous animals, also

occur. M. Morren has discovered in the peat of Flanders the bones of

otters and beavers[1021]; but no remains have been met with belonging to

those extinct quadrupeds, of which the living congeners inhabit warmer

latitudes, such as the elephant, rhinoceros, hippopotamus, hyaena, and

tiger, though these are so common in superficial deposits of silt, mud,

sand, or stalactite, in various districts throughout Great Britain.

Their absence seems to imply that they had ceased to live before the

atmosphere of this part of the world acquired that cold and humid

character which favors the growth of peat.

_Remains of ships, &c., in peat mosses._--From the facts before

mentioned, that mosses occasionally burst, and descend in a fluid state

to lower levels, it will readily be seen that lakes and arms of the sea

may occasionally become the receptacles of drift peat. Of this,

accordingly, there are numerous examples; and hence the alternations of

clay and sand with different deposits of peat so frequent on some

coasts, as on those of the Baltic and German Ocean. We are informed by

Deguer, that remains of ships, nautical instruments, and oars, have been

found in many of the Dutch mosses; and Gerard, in his History of the

Valley of the Somme, mentions that in the lowest tier of that moss was

found a boat loaded with bricks, proving that these mosses were at one

period navigable lakes and arms of the sea, as were also many mosses on

the coast of Picardy, Zealand, and Friesland, from which soda and salt

are procured.[1022] The canoes, stone hatchets, and stone arrow-heads

found in peat in different parts of Great Britain, lead to similar

conclusions.

_Imbedding of human and other remains, and works of Art, in Blown Sand._

The drifting of sand may next be considered among the causes capable of

preserving organic remains and works of art on the emerged land.

_African Sands._--The sands of the African deserts have been driven by

the west winds over part of the arable land of Egypt, on the western

bank of the Nile, in those places where valleys open into the plain, or

where there are gorges through the Libyan mountains. By similar

sand-drifts the ruins of ancient cities have been buried between the

temple of Jupiter Ammon and Nubia. M. G. A. De Luc attempted to infer

the recent origin of our continents, from the fact that these moving

sands have arrived only in modern times at the fertile plains of the

Nile. The same scourge, he said, would have afflicted Egypt for ages

anterior to the times of history, had the continents risen above the

level of the sea several hundred centuries before our era.[1023] But the

author proceeded in this, as in all his other chronological

computations, on a multitude of gratuitous assumptions. He ought, in the

first place, to have demonstrated that the whole continent of Africa was

raised above the level of the sea at one period; for unless this point

was established, the region from whence the sands began to move might

have been the last addition made to Africa, and the commencement of the

sand-flood might have been long posterior to the laying dry of the

greater portion of that continent. That the different parts of Europe

were not all elevated at one time is now generally admitted. De Luc

should also have pointed out the depth of drift sand in various parts of

the great Libyan deserts, and have shown whether any valleys of large

dimensions had been filled up--how long these may have arrested the

progress of the sands, and how far the flood had upon the whole advanced

since the times of history.

We have seen that Sir J. G. Wilkinson is of opinion that, while the

sand-drift is making aggressions at certain points upon the fertile soil

of Egypt, the alluvial deposit of the Nile is advancing very generally

upon the desert; and that, upon the whole, the balance is greatly in

favor of the fertilizing mud.[1024]

No mode of interment can be conceived, more favorable to the

conservation of monuments for indefinite periods than that now so common

in the region immediately westward of the Nile. The sand which

surrounded and filled the great temple of Ipsambul, first discovered by

Burckhardt, and afterwards partially uncovered by Belzoni and Beechey,

was so fine as to resemble a fluid when put in motion. Neither the

features of the colossal figures, nor the color of the stucco with which

some were covered, nor the paintings on the walls, had received any

injury from being enveloped for ages in this dry impalpable dust.[1025]

At some future period, perhaps when the pyramids shall have perished,

the action of the sea, or an earthquake, may lay open to the day some of

these buried temples. Or we may suppose the desert to remain

undisturbed, and changes in the surrounding sea and land to modify the

climate and the direction of the prevailing winds, so that these may

then waft away the Libyan sands as gradually as they once brought them

to those regions. Thus, many a town and temple of higher antiquity than

Thebes or Memphis may reappear in their original antiquity, and a part

of the gloom which overhangs the history of the earlier nations be

dispelled.

Whole caravans are said to have been overwhelmed by the Libyan sands;

and Burckhardt informs us that "after passing the Akaba near the head of

the Red Sea, the bones of dead camels are the only guides of the pilgrim

through the wastes of sand."--"We did not see," says Captain Lyon,

speaking of a plain near the Soudah mountains, in Northern Africa, "the

least appearance of vegetation; but observed many skeletons of animals,

which had died of fatigue on the desert, and occasionally the grave of

some human being. All these bodies were so dried by the heat of the sun,

that putrefaction appears not to have taken place after death. In

recently expired animals I could not perceive the slightest offensive

smell; and in those long dead, the skin with the hair on it remained

unbroken and perfect, although so brittle as to break with a slight

blow. The sand-winds never cause these carcases to change their places;

for, in a short time, a slight mound is formed round them, and they

become stationary."[1026]

_Towns overwhelmed by sand floods._--The burying of several towns and

villages in England, France, and Jutland, by blown sand, is on record;

thus, for example, near St. Pol de Leon, in Brittany, a whole village

was completely buried beneath drift sand, so that nothing was seen but

the spire of the church.[1027] In Jutland marine shells adhering to

sea-weed are sometimes blown by the violence of the wind to the height

of 100 feet, and buried in similar hills of sand.

In Suffolk, in the year 1688, part of Downham was overwhelmed by sands

which had broken loose about 100 years before, from a warren five miles

to the south-west. This sand had, in the course of a century, travelled

five miles, and covered more than 1000 acres of land.[1028] A

considerable tract of cultivated land on the north coast of Cornwall has

been inundated by drift sand, forming hills several hundred feet above

the level of the sea, and composed of comminuted marine shells, in

which some terrestrial shells are enclosed entire. By the shifting of

these sands the ruins of ancient buildings have been discovered; and in

some cases where wells have been bored to a great depth, distinct

strata, separated by a vegetable crust, are visible. In some places, as

at New Quay, large masses have become sufficiently indurated to be used

for architectural purposes. The lapidification, which is still in

progress, appears to be due to oxide of iron held in solution by the

water which percolates the sand.[1029]

_Imbedding of Organic and other Remains in Volcanic Formations on the

Land._

I have in some degree anticipated the subject of this section in former

chapters, when speaking of the buried cities around Naples, and those on

the flanks of Etna (pp. 385. 400.). From the facts referred to, it

appeared that the preservation of human remains and works of art is

frequently due to the descent of floods caused by the copious rains

which accompany eruptions. These aqueous lavas, as they are called in

Campania, flow with great rapidity, and in 1822 surprised and

suffocated, as was stated, seven persons in the villages of St.

Sebastian and Massa, on the flanks of Vesuvius.

In the tuffs, moreover, or solidified mud, deposited by these aqueous

lavas, impressions of leaves and of trees have been observed. Some of

those, formed after the eruption of Vesuvius in 1822, are now preserved

in the museum at Naples.

Lava itself may become indirectly the means of preserving terrestrial

remains, by overflowing beds of ashes, pumice, and ejected matter, which

may have been showered down upon animals and plants, or upon human

remains. Few substances are better non-conductors of heat than volcanic

dust and scoriae, so that a bed of such materials is rarely melted by a

superimposed lava-current. After consolidation, the lava affords secure

protection to the lighter and more removable mass below, in which the

organic relics may be enveloped. The Herculanean tuffs containing the

rolls of papyrus, of which the characters are still legible, have, as

was before remarked, been for ages covered by lava.

Another mode by which lava may tend to the conservation of imbedded

remains, at least of works of human art, is by its overflowing them when

it is not intensely heated, in which case they sometimes suffer little

or no injury.

Thus when the Etnean lava-current of 1669 covered fourteen towns and

villages, and part of the city of Catania, it did not melt down a great

number of statues and other articles in the vaults of Catania; and at

the depth of thirty-five feet in the same current, on the site of

Mompiliere, one of the buried towns, the bell of a church and some

statues were found uninjured (p. 401.).

We read of several buried cities in Central India, and among others of

Oujein (or Oojain) which about fifty years before the Christian era was

the seat of empire, of art, and of learning; but which in the time of

the Rajah Vicramaditya, was overwhelmed, according to tradition,

together with more than eighty other large towns in the provinces of

Malwa and Bagur, "by a shower of earth." The city which now bears the

name is situated a mile to the southward of the ancient town. On digging

on the spot where the latter is supposed to have stood, to the depth of

fifteen or eighteen feet, there are frequently discovered, says Mr.

Hunter, entire brick walls, pillars of stone, and pieces of wood of an

extraordinary hardness, besides utensils of various kinds, ancient

coins, and occasionally buried wheat in a state resembling

charcoal.[1030]

The soil which covers Oujein is described as "being of an ash-gray

color, with minute specks of black sand."[1031] And the "shower of

earth," said to have "fallen from heaven," has been attributed by some

travellers to volcanic agency. There are, however, no active volcanoes

in Central India, the nearest to Oujein being Denodur hill near Bhooj,

the capital of Cutch, 300 geographical miles distant, if indeed that

hill has ever poured out lava in historical times, which is doubted by

many.[1032] The latest writers on Oujein avow their suspicion that the

supposed "catastrophe" was nothing more than the political decline and

final abandonment of a great city which, like Nineveh or Babylon, and

many an ancient seat of empire in the East, after losing its importance

as a metropolis, became a heap of ruins. The rapidity with which the

sun-dried bricks, of which even the most splendid oriental palaces are

often constructed, crumble down when exposed to rain and sun, and are

converted into mounds of ordinary earth and clay, is well known.

According to Captain Dangerfield, trap tuff and columnar basalt

constitute the rocks in the environs of Oujein[1033], and the volcanic

nature of these formations, from which the materials of the bricks were

originally derived, may have led to the idea of the city having been

overwhelmed by a volcanic eruption.

CHAPTER XLVI.

BURYING OF FOSSILS IN ALLUVIAL DEPOSITS AND IN CAVES.

Fossils in alluvium--Effects of sudden inundations--terrestrial

animals most abundantly preserved in alluvium where earthquakes

prevail--Marine alluvium--Buried town--Effects of Landslips--Organic

remains in fissures and caves--Form and dimensions of caverns--their

probable origin--Closed basins and subterranean rivers of the

Morea--Katavothra--Formation of breccias with red cement--Human

remains imbedded in Morea--Intermixture, in caves of South of France

and elsewhere, of human remains and bones of extinct quadrupeds, no

proof of former co-existence of man with those lost species.

_Fossils in alluvium._--The next subject for our consideration,

according to the division before proposed, is the embedding of organic

bodies in alluvium.

The gravel, sand, and mud in the bed of a river does not often contain

any animal or vegetable remains; for the whole mass is so continually

shifting its place, and the attrition of the various parts is so great,

that even the hardest rocks contained in it are, at length, ground down

to powder. But when sand and sediment are suddenly swept by a flood, and

then let fall upon the land, such an alluvium may envelop trees or the

remains of animals, which, in this manner, are often permanently

preserved. In the mud and sand produced by the floods in Scotland, in

1829, the dead and mutilated bodies of hares, rabbits, moles, mice,

partridges, and even the bodies of men, were found partially

buried.[1034] But in these and similar cases one flood usually effaces

the memorials left by another, and there is rarely a sufficient depth of

undisturbed transported matter, in any one spot, to preserve the organic

remains for ages from destruction.

Where earthquakes prevail, and the levels of a country are changed from

time to time, the remains of animals may more easily be inhumed and

protected from disintegration. Portions of plains, loaded with alluvial

accumulations by transient floods, may be gradually upraised; and, if

any organic remains have been imbedded in the transported materials,

they may, after such elevation, be placed beyond the reach of the

erosive power of streams. In districts where the drainage is repeatedly

deranged by subterranean movements, every fissure, every hollow caused

by the sinking in of land, becomes a depository of organic and inorganic

substances, hurried along by transient floods.

_Marine alluvium._--In May, 1787, a dreadful inundation of the sea was

caused at Coringa, Ingeram, and other places, on the coast of

Coromandel, in the East Indies, by a hurricane blowing from the N. E.,

which raised the waters so that they rolled inland to the distance of

about twenty miles from the shore, swept away many villages, drowned

more than 10,000 people, and left the country covered with marine mud,

on which the carcasses of about 100,000 head of cattle were strewed. An

old tradition of the natives of a similar flood, said to have happened

about a century before, was, till this event, regarded as fabulous by

the European settlers.[1035] The same coast of Coromandel was, so late

as May, 1832, the scene of another catastrophe of the same kind; and

when the inundation subsided, several vessels were seen grounded in the

fields of the low country about Coringa.

Many of the storms termed hurricanes have evidently been connected with

submarine earthquakes, as is shown by the atmospheric phenomena

attendant on them, and by the sounds heard in the ground and the odors

emitted. Such were the circumstances which accompanied the swell of the

sea in Jamaica, in 1780, when a great wave desolated the western coast,

and bursting upon Savanna la Mar, swept away the whole town in an

instant, so that not a vestige of man, beast, or habitation, was seen

upon the surface.[1036]

_Houses and works of art in alluvial deposits._--A very ancient

subterranean town, apparently of Hindoo origin, was discovered in India

in 1833, in digging the Doab canal. Its site is north of Saharunpore,

near the town of Behat, and seventeen feet below the present surface of

the country. More than 170 coins of silver and copper have already been

found, and many articles in metal and earthenware. The overlying deposit

consisted of about five feet of river sand, with a substratum about

twelve feet thick of red alluvial clay. In the neighborhood are several

rivers and torrents, which descend from the mountains charged with vast

quantities of mud, sand, and shingle; and within the memory of persons

now living the modern Behat has been threatened by an inundation, which,

after retreating, left the neighboring country strewed over with a

superficial covering of sand several feet thick. In sinking wells in the

environs, masses of shingle and boulders have been reached resembling

those now in the river-channels of the same district, under a deposit of

thirty feet of reddish loam. Captain Cautley, therefore, who directed

the excavations, supposes that the matter discharged by torrents has

gradually raised the whole country skirting the base of the lower hills;

and that the ancient town, having been originally built in a hollow, was

submerged by floods, and covered over with sediment seventeen feet in

thickness.[1037]

We are informed, by M. Boblaye, that in the Morea, the formation termed

caramique, consisting of pottery, tiles, and bricks, intermixed with

various works of art, enters so largely into the alluvium and vegetable

soil upon the plains of Greece, and into hard and crystalline breccias

which have been formed at the foot of declivities, that it constitutes

an important stratum which might, in the absence of zoological

characters, serve to mark our epoch in a most indestructible

manner.[1038]

_Landslips._--The landslip, by suddenly precipitating large masses of

rock and soil into a valley, overwhelms a multitude of animals, and

sometimes buries permanently whole villages, with their inhabitants and

large herds of cattle. Thus three villages, with their entire

population, were covered, when the mountain of Piz fell in 1772, in the

district of Treviso, in the state of Venice,[1039] and part of Mount

Grenier, south of Chambery, in Savoy, which fell down in the year 1248,

buried five parishes, including the town and church of St. Andra, the

ruins occupying an extent of about nine square miles.[1040]

The number of lives lost by the slide of the Rossberg, in Switzerland,

in 1806, was estimated at more than 800, a great number of the bodies,

as well as several villages and scattered houses, being buried deep

under mud and rock. In the same country, several hundred cottages, with

eighteen of their inhabitants and a great number of cows, goats, and

sheep, were victims to the sudden fall of a bed of stones, thirty yards

deep, which descended from the summits of the Diablerets in Vallais. In

the year 1618, a portion of Mount Conto fell, in the county of

Chiavenna, in Switzerland, and buried the town of Pleurs with all its

inhabitants, to the number of 2430.

It is unnecessary to multiply examples of similar local catastrophes,

which however numerous they may have been in mountainous parts of

Europe, within the historical period, have been, nevertheless, of rare

occurrence when compared to events of the same kind which have taken

place in regions convulsed by earthquakes. It is then that enormous

masses of rock and earth, even in comparatively low and level countries,

are detached from the sides of valleys, and cast down into the river

courses, and often so unexpectedly that they overwhelm, even in the

daytime, every living thing upon the plains.

_Preservation of Organic Remains in Fissures and Caves._

In the history of earthquakes it was shown that many hundreds of new

fissures and chasms had opened in certain regions during the last 150

years, some of which are described as being of unfathomable depth. We

also perceive that mountain masses have been violently fractured and

dislocated, during their rise above the level of the sea; and thus we

may account for the existence of many cavities in the interior of the

earth by the simple agency of earthquakes; but there are some caverns,

especially in limestone rocks, which, although usually, if not always,

connected with rents, are nevertheless of such forms, and dimensions,

alternately expanding into spacious chambers, and then contracting again

into narrow passages, that it is difficult to conceive that they can owe

their origin to the mere fracturing and displacement of solid masses.

In the limestone of Kentucky, in the basin of Green River, one of the

tributaries of the Ohio, a line of underground cavities has been traced

in one direction for a distance of ten miles, without any termination;

and one of the chambers, of which there are many, all connected by

narrow tunnels, is no less than ten acres in area and 150 feet in its

greatest height. Besides the principal series of "antres vast," there

are a great many lateral embranchments not yet explored.[1041]

The cavernous structure here alluded to is not altogether confined to

calcareous rocks; for it has lately been observed in micaceous and

argillaceous schist in the Grecian island of Thermia (Cythnos of the

ancients), one of the Cyclades. Here also spacious halls, with rounded

and irregular walls, are connected together by narrow passages or

tunnels, and there are many lateral branches which have no outlet. A

current of water has evidently at some period flowed through the whole,

and left a muddy deposit of bluish clay upon the floor; but the erosive

action of the stream cannot be supposed to have given rise to the

excavations in the first instance. M. Virlet suggests that fissures were

first caused by earthquakes, and that these fissures became the chimneys

or vents for the disengagement of gas, generated below by volcanic heat.

Gases, he observes, such as the muriatic, sulphuric, fluoric, and

others, might, if raised to a high temperature, alter and decompose the

rocks which they traverse. There are signs of the former action of such

vapors in rents of the micaceous schist of Thermia, and thermal springs

now issue from the grottoes of that island. We may suppose that

afterwards the elements of the decomposed rocks were gradually removed

in a state of solution by mineral waters; a theory which, according to

M. Virlet, is confirmed by the effect of heated gases which escape from

rents in the isthmus of Corinth, and which have greatly altered and

corroded the hard siliceous and jaspideous rocks.[1042]

When we reflect on the quantity of carbonate of lime annually poured out

by mineral waters, we are prepared to admit that large cavities must, in

the course of ages, be formed at considerable depths below the surface

in calcareous rocks.[1043] These rocks, it will be remembered, are at

once more soluble, more permeable, and more fragile, than any others, at

least all the compact varieties are very easily broken by the movements

of earthquakes, which would produce only flexures in argillaceous

strata. Fissures once formed in limestone are not liable, as in many

other formations, to become closed up by impervious clayey matter, and

hence a stream of acidulous water might for ages obtain a free and

unobstructed passage.[1044]

_Morea._--Nothing is more common in limestone districts than the

engulfment of rivers, which after holding a subterranean course for many

miles escape again by some new outlet. As they are usually charged with

fine sediment, and often with sand and pebbles where they enter, whereas

they are usually pure and limpid where they flow out again, they must

deposit much matter in empty spaces in the interior of the earth. In

addition to the materials thus introduced, stalagmite, or carbonate of

lime, drops from the roofs of caverns, and in this mixture the bones of

animals washed in by rivers are often entombed. In this manner we may

account for those bony breccias which we often find in caves, some of

which are of high antiquity while others are very recent and in daily

progress. In no district are engulfed streams more conspicuous than in

the Morea, where the phenomena attending them have been lately studied

and described in great detail by M. Boblaye and his fellow-laborers of

the French expedition to Greece.[1045] Their account is peculiarly

interesting to geologists, because it throws light on the red osseous

breccias containing the bones of extinct quadrupeds which are so common

in almost all the countries bordering the Mediterranean. It appears that

the numerous caverns of the Morea occur in a compact limestone, of the

age of the English chalk, immediately below which are arenaceous strata

referred to the period of our greensand. In the more elevated districts

of that peninsula there are many deep land-locked valleys, or basins,

closed round on all sides by mountains of fissured and cavernous

limestone. The year is divided almost as distinctly as between the

tropics into a rainy season, which lasts upwards of four months, and a

season of drought of nearly eight months' duration. When the torrents

are swollen by the rains, they rush from surrounding heights into the

inclosed basins; but, instead of giving rise to lakes, as would be the

case in most other countries, they are received into gulfs or chasms,

called by the Greeks "Katavothra," and which correspond to what are

termed "swallow-holes" in the north of England. The water of these

torrents is charged with pebbles and red ochreous earth, resembling

precisely the well-known cement of the osseous breccias of the

Mediterranean. It dissolves in acids with effervescence, and leaves a

residue of hydrated oxide of iron, granular iron, impalpable grains of

silex, and small crystals of quartz. Soil of the same description

abounds everywhere on the surface of the decomposing limestone in

Greece, that rock containing in it much siliceous and ferruginous

matter.

Many of the Katavothra being insufficient to give passage to all the

water in the rainy season, a temporary lake is formed round the mouth of

the chasm, which then becomes still farther obstructed by pebbles, sand,

and red mud, thrown down from the turbid waters. The lake being thus

raised, its waters generally escape through other openings, at higher

levels, around the borders of the plain, constituting the bottom of the

closed basin.

In some places, as at Kavaros and Tripolitza, where the principal

discharge is by a gulf in the middle of the plain, nothing can be seen

over the opening in summer, when the lake dries up, but a deposit of red

mud, cracked in all directions. But the Katavothron is more commonly

situated at the foot of the surrounding escarpment of limestone; and in

that case there is sometimes room enough to allow a person to enter, in

summer, and even to penetrate far into the interior. Within is seen a

suite of chambers, communicating with each other by narrow passages; and

M. Virlet relates, that in one instance he observed, near the entrance,

human bones imbedded in recent red mud, mingled with the remains of

plants and animals of species now inhabiting the Morea. It is not

wonderful, he says, that the bones of man should be met with in such

receptacles; for so murderous have been the late wars in Greece, that

skeletons are often seen lying exposed on the surface of the

country.[1046]

In summer, when no water is flowing into the Katavothron, its mouth,

half closed up with red mud, is masked by a vigorous vegetation, which

is cherished by the moisture of the place. It is then the favorite

hiding-place and den of foxes and jackals; so that the same cavity

serves at one season of the year for the habitation of carnivorous

beasts, and at another as the channel of an engulfed river. Near the

mouth of one chasm, M. Boblaye and his companions saw the carcass of a

horse, in part devoured, the size of which seemed to have prevented the

jackals from dragging it in: the marks of their teeth were observed on

the bones, and it was evident that the floods of the ensuing winter

would wash in whatsoever might remain of the skeleton.

It has been stated that the waters of all these torrents of the Morea

are turbid where they are engulfed; but when they come out again, often

at the distance of many leagues, they are perfectly clear and limpid,

being only charged occasionally with a slight quantity of calcareous

sand. The points of efflux are usually near the sea-shores of the Morea,

but sometimes they are submarine; and when this is the case, the sands

are seen to boil up for a considerable space, and the surface of the

sea, in calm weather, swells in large convex waves. It is curious to

reflect, that when this discharge fails in seasons of drought, the

pressure of the sea may force its salt waters into subterraneous

caverns, and carry in marine sand and shells, to be mingled with

ossiferous mud, and the remains of terrestrial animals.

In general, however, the efflux of water at these inferior openings is

surprisingly uniform. It seems, therefore, that the large caverns in the

interior must serve as reservoirs, and that the water escapes gradually

from them, in consequence of the smallness of the rents and passages by

which they communicate with the surface.

The phenomena above described are not confined to the Morea, but occur

in Greece generally, and in those parts of Italy, Spain, Asia Minor, and

Syria, where the formations of the Morea extend. The Copaic lake in

Boeotia has no outlet, except by underground channels; and hence we

can explain those traditional and historical accounts of its having

gained on the surrounding plains and overflowed towns, as such floods

must have happened whenever the outlet was partially choked up by mud,

gravel, or the subsidence of rocks, caused by earthquakes. When speaking

of the numerous fissures in the limestone of Greece, M. Boblaye reminds

us of the famous earthquake of 469 B.C., when, as we learn from Cicero,

Plutarch, Strabo, and Pliny, Sparta was laid in ruins, part of the

summit of Mount Taygetus torn off, and numerous gulfs and fissures

caused in the rocks of Laconia.

During the great earthquake of 1693, in Sicily, several thousand people

were at once entombed in the ruins of caverns in limestone, at Sortino

Vecchio; and, at the same time, a large stream, which had issued for

ages from one of the grottoes below that town, changed suddenly its

subterranean course, and came out from the mouth of a cave lower down

the valley, where no water had previously flowed. To this new point the

ancient water-mills were transferred, as I learnt when I visited the

spot in 1829.

When the courses of engulfed rivers are thus liable to change, from time

to time, by alterations in the levels of a country, and by the rending

and shattering of mountain masses, we must suppose that the dens of wild

beasts will sometimes be inundated by subterranean floods, and their

carcasses buried under heaps of alluvium. The bones, moreover, of

individuals which have died in the recesses of caves, or of animals

which have been carried in for prey, may be drifted along, and mixed up

with mud, sand, and fragments of rocks, so as to form osseous breccias.

In 1833 I had an opportunity of examining the celebrated caves of

Franconia, and among others that of Rabenstein, newly discovered. Their

general form, and the nature and arrangement of their contents, appeared

to me to agree perfectly with the notion of their having once served as

the channels of subterranean rivers. This mode of accounting for the

introduction of transported matter into the Franconian and other caves,

filled up as they often are even to their roofs with osseous breccia,

was long ago proposed by M. C. Prevost,[1047] and seems at length to be

very generally adopted. But I do not doubt that bears inhabited some of

the German caves, or that the cavern of Kirkdale, in Yorkshire, was once

the den of hyaenas. The abundance of bony dung, associated with hyaenas'

bones, has been pointed out by Dr. Buckland, and with reason, as

confirmatory of this opinion.

The same author observed in every cave examined by him in Germany, that

deposits of mud and sand, with or without rolled pebbles and angular

fragments of rock, were covered over with a _single_ crust of

stalagmite.[1048] In the English caves he remarked a similar absence of

_alterations_ of alluvium and stalagmite. But Dr. Schmerling has

discovered in a cavern at Chockier, about two leagues from Liege, three

distinct beds of stalagmite, and between each of them a mass of breccia,

and mud mixed with quartz pebbles, and in the three deposits the bones

of extinct quadrupeds.[1049]

This exception does not invalidate the generality of the phenomenon

pointed out by Dr. Buckland, one cause of which may perhaps be this,

that if several floods pass at different intervals of time through a

subterranean passage, the last, if it has power to drift along fragments

of rock, will also tear up any alternating stalagmitic and alluvial beds

that may have been previously formed. Another cause may be, that a

particular line of caverns will rarely be so situated, in relation to

the lowest levels of a country, as to become, at two distinct epochs,

the receptacle of engulfed rivers; and if this should happen, some of

the caves, or at least the tunnels of communication, may at the first

period be entirely choked up with transported matter, so as not to allow

the subsequent passage of water in the same direction.

As the same chasms may remain open throughout periods of indefinite

duration, the species inhabiting a country may in the meantime be

greatly changed, and thus the remains of animals belonging to very

different epochs may become mingled together in a common tomb. For this

reason it is often difficult to separate the monuments of the human

epoch from those relating to periods long antecedent, and it was not

without great care and skill that Dr. Buckland was enabled to guard

against such anachronisms in his investigations of several of the

English caves. He mentions that human skeletons were found in the cave

of Wokey Hole, near Wells, in the Mendips, dispersed through reddish mud

and clay, and some of them united by stalagmite into a firm osseous

breccia. "The spot on which they lie is within reach of the highest

floods of the adjacent river, and the mud in which they are buried is

evidently fluviatile."[1050]

In speaking of the cave of Paviland on the coast of Glamorganshire the

same author states that the entire mass through which bones were

dispersed appeared to have been disturbed by ancient diggings, so that

the remains of extinct animals had become mixed with recent bones and

shells. In the same cave was a human skeleton, and the remains of recent

testacea of eatable species, which may have been carried in by man.

In several caverns on the banks of the Meuse, near Liege, Dr. Schmerling

has found human bones in the same mud and breccia with those of the

elephant, rhinoceros, bear, and other quadrupeds of extinct species. He

has observed none of the dung of any of these animals: and from this

circumstance, and the appearance of the mud and pebbles, he concludes

that these caverns were never inhabited by wild beasts, but washed in by

a current of water. As the human skulls and bones were in fragments, and

no entire skeleton had been found, he does not believe that these caves

were places of sepulture, but that the human remains were washed in at

the same time as the bones of extinct quadrupeds, and that these lost

species of mammalia co-existed on the earth with man.

_Caverns in the south of France._--Similar associations in the south of

France, of human bones and works of art, with remains of extinct

quadrupeds, have induced other geologists to maintain that man was an

inhabitant of that part of Europe before the rhinoceros, hyaena, tiger,

and many fossil species disappeared. I may first mention the cavern of

Bize, in the department of Aude, where M. Marcel de Serres met with a

small number of human bones mixed with those of extinct animals and with

land shells. They occur in a calcareous stony mass, bound together by a

cement of stalagmite. On examining the same caverns, M. Tournal found

not only in these calcareous beds, but also in a black mud which

overlies a red osseous mud, several human teeth, together with broken

angular fragments of a rude kind of pottery, and also recent marine and

terrestrial shells. The teeth preserve their enamel; but the fangs are

so much altered as to adhere strongly when applied to the tongue. Of the

terrestrial shells thus associated with the bones and pottery, the most

common are _Cyclostoma elegans_, _Bulimus decollatus_, _Helix

nemoralis_, and _H. nitida_. Among the marine are found _Pecten

jacobaeus_, _Mytilus edulis_, and _Natica mille-punctata_, all of them

eatable kinds, and which may have been brought there for food. Bones

were found in the same mass belonging to three new species of deer, the

brown bear (_Ursus arctoideus_), and the wild bull (_Bos urus_),

formerly a native of Germany.[1051]

In the same parts of France, M. de Christol has found in caverns in a

tertiary limestone at Pondres and Souvignargues, two leagues north of

Lunel-viel, in the department of Herault, human bones and pottery

confusedly mixed with remains of the rhinoceros, bear, hyaena, and other

terrestrial mammifers. They were imbedded in alluvial mud, of the

solidity of calcareous tufa, and containing some flint pebbles and

fragments of the limestone of the country. Beneath this mixed

accumulation, which sometimes attained a thickness of thirteen feet, is

the original floor of the cavern, about a foot thick, covered with bones

and the dung of animals (_album graecum_), in a sandy and tufaceous

cement.

The human bones in these caverns of Pondres and Souvignargues were

found, upon a careful analysis, to have parted with their animal matter

to as great a degree as those of the hyaena which accompany them, and are

equally brittle, and adhere as strongly to the tongue.

In order to compare the degree of alteration of these bones with those

known to be of high antiquity, M. Marcel de Serres and M. Ballard,

chemists of Montpelier, procured some from a Gaulish sarcophagus, in the

plain of Lunel, supposed to have been buried for fourteen or fifteen

centuries at least. In these the cellular tissue was empty, but they

were more solid than fresh bones. They did not adhere to the tongue in

the same manner as those of the caverns of Bize and Pondres, yet they

had lost at least three fourths of their original animal matter.

The superior solidity of the Gaulish bones to those in a fresh skeleton

is a fact in perfect accordance with the observations made by Dr.

Mantell on bones taken from a Saxon tumulus near Lewes.

M. Tessier has also described a cavern near Mialet, in the department

of Gard, where the remains of the bear and other animals were mingled

confusedly with human bones, coarse pottery, teeth pierced for amulets,

pointed fragments of bone, bracelets of bronze, and a Roman urn. Part of

this deposit reached to the roof of the cavity, and adhered firmly to

it. The author suggests that the exterior portion of the grotto may at

one period have been a den of bears, and that afterwards the aboriginal

inhabitants of the country took possession of it either for a dwelling

or a burial-place, and left there the coarse pottery, amulets, and

pointed pieces of bone. At a third period the Romans may have used the

cavern as a place of sepulture or concealment, and to them may have

belonged the urn and bracelets of metal. If we then suppose the course

of the neighboring river to be impeded by some temporary cause, a flood

would be occasioned, which, rushing into the open grotto, may have

washed all the remains into the interior caves and tunnels, heaping the

whole confusedly together.[1052]

In the controversy which has arisen on this subject, MM. Marcel de

Serres, De Christol, Tournal, and others, have contended, that the

phenomena of this and other caverns in the south of France prove that

the fossil rhinoceros, hyaena, bear, and several other lost species, were

once contemporaneous inhabitants of the country, together with man;

while M. Desnoyers has supported the opposite opinion. The flint

hatchets and arrow-heads, he says, and the pointed bones and coarse

pottery of many French and English caves, agree precisely in character

with those found in the tumuli, and under the dolmens (rude altars of

unhewn stone) of the primitive inhabitants of Gaul, Britain, and

Germany. The human bones, therefore, in the caves which are associated

with such fabricated objects, must belong not to antediluvian periods,

but to a people in the same stage of civilization as those who

constructed the tumuli and altars.

In the Gaulish monuments we find, together with the objects of industry

above mentioned, the bones of wild and domestic animals of species now

inhabiting Europe, particularly of deer, sheep, wild-boars, dogs,

horses, and oxen. This fact has been ascertained in Quercy, and other

provinces; and it is supposed by antiquaries that the animals in

question were placed beneath the Celtic altars in memory of sacrifices

offered to the Gaulish divinity Hesus, and in the tombs to commemorate

funeral repasts, and also from a supposition prevalent among savage

nations, which induces them to lay up provisions for the manes of the

dead in a future life. But in none of these ancient monuments have any

bones been found of the elephant, rhinoceros, hyaena, tiger, and other

quadrupeds, such as are found in caves, as might certainly have been

expected had these species continued to flourish at the time that this

part of Gaul was inhabited by man.[1053]

We are also reminded by M. Desnoyers of a passage in Florus, in which it

is related that Caesar ordered the caves into which the Aquitanian Gauls

had retreated to be closed up.[1054] It is also on record, that so late

as the eighth century, the Aquitanians defended themselves in caverns

against King Pepin. As many of these caverns, therefore, may have served

in succession as temples and habitations, as places of sepulture,

concealment, or defence, it is easy to conceive that human bones, and

those of animals, in osseous breccias of much older date, may have been

swept away together, by inundations, and then buried in one promiscuous

heap.

It is not on the evidence of such intermixtures that we ought readily to

admit either the high antiquity of the human race, or the recent date of

certain lost species of quadrupeds.

Among the various modes in which the bones of animals become preserved,

independently of the agency of land floods and engulfed rivers, I may

mention that open fissures often serve as natural pitfalls in which

herbivorous animals perish. This may happen the more readily when they

are chased by beasts of prey, or when surprised while carelessly

browsing on the shrubs which so often overgrow and conceal the edges of

fissures.[1055]

During the excavations recently made near Behat in India, the bones of

two deer were found at the bottom of an ancient well which had been

filled up with alluvial loam. Their horns were broken to pieces, but the

jaw bones and other parts of the skeleton remained tolerably perfect.

"Their presence," says Captain Cautley, "is easily accounted for, as a

great number of these and other animals are constantly lost in galloping

over the jungles and among the high grass by falling into deserted

wells."[1056]

Above the village of Selside, near Ingleborough in Yorkshire, a chasm of

enormous but unknown depth occurs in the scar-limestone, a member of the

carboniferous series. "The chasm," says Professor Sedgwick, "is

surrounded by grassy shelving banks, and many animals, tempted towards

its brink, have fallen down and perished in it. The approach of cattle

is now prevented by a strong lofty wall; but there can be no doubt that,

during the last two or three thousand years, great masses of bony

breccia must have accumulated in the lower parts of the great fissure,

which probably descends through the whole thickness of the

scar-limestone, to the depth of perhaps five or six hundred feet."[1057]

When any of these natural pit-falls happen to communicate with lines of

subterranean caverns, the bones, earth, and breccia, may sink by their

own weight, or be washed into the vaults below.

At the north extremity of the rock of Gibraltar are perpendicular

fissures, on the ledges of which a number of hawks nestle and rear their

young in the breeding season. They throw down from their nests the bones

of small birds, mice, and other animals, on which they feed, and these

are gradually united into a breccia of angular fragments of the

decomposing limestone with a cement of red earth.

At the pass of Escrinet in France, on the northern escarpment of the

Coiron hills, near Aubenas, I have seen a breccia in the act of forming.

Small pieces of disintegrating limestone are transported, during heavy

rains, by a streamlet, to the foot of the declivity, where land shells

are very abundant. The shells and pieces of stone soon become cemented

together by stalagmite into a compact mass, and the talus thus formed is

in one place fifty feet deep, and five hundred yards wide. So firmly is

the lowest portion consolidated, that it is quarried for mill-stones.

_Recent, stalagmitic limestone of Cuba._--One of the most singular

examples of the recent growth of stalagmitic limestone in caves and

fissures is that described by Mr. R. C. Taylor, as observable on the

north-east part of the island of Cuba.[1058] The country there is

composed of a white marble, in which are numerous cavities, partially

filled with a calcareous deposit of a brick-red color. In this red

deposit are shells, or often the hollow casts of shells, chiefly

referable to eight or nine species of land snails, a few scattered bones

of quadrupeds, and, what is still more singular, marine univalve shells,

often at the height of many hundred, or even one thousand feet above the

sea. The following explanation is given of the gradual increase of this

deposit. Land snails of the genera Helix, Cyclostoma, Pupa, and

Clausilia, retire into the caves, the floors of which are strewed with

myriads of their dead and unoccupied shells, at the same time that water

infiltered through the mountain throws down carbonate of lime,

enveloping the shells, together with fragments of the white limestone

which occasionally falls from the roof. Multitudes of bats resort to the

caves; and their dung, which is of a bright red color, (probably derived

from the berries on which they feed,) imparts its red hue to the mass.

Sometimes also the Hutia, or great Indian rat of the island, dies and

leaves its bones in the caves. "At certain seasons the soldier-crabs

resort to the sea-shore, and then return from their pilgrimage, each

carrying with them, or rather dragging, the shell of some marine

univalve for many a weary mile. They may be traced even at the distance

of eight or ten miles from the shore, on the summit of mountains 1200

feet high, like the pilgrims of the olden times, each bearing his shell

to denote the character and extent of his wanderings." By this means

several species of marine testacea of the genera Trochus, Turbo,

Littorina, and Monodonta, are conveyed into inland caverns, and enter

into the composition of the newly formed rock.

CHAPTER XLVII.

IMBEDDING OF ORGANIC REMAINS IN SUBAQUEOUS DEPOSITS.

Division of the subject--Imbedding of terrestrial animals and

plants--Increased specific gravity of wood sunk to great depths in

the sea--Drift-timber of the Mackenzie in Slave Lake and Polar

Sea--Floating trees in the Mississippi--in the Gulf Stream--on the

coast of Iceland, Spitzbergen, and Labrador--Submarine

forests--Example on coast of Hampshire--Mineralization of

plants--Imbedding of marine plants--of insects--of reptiles--Bones

of birds why rare--Imbedding of terrestrial quadrupeds by river

floods--Skeletons in recent shell marl--Imbedding of mammiferous

remains in marine strata.

_Division of the subject._--Having treated of the imbedding of organic

remains in deposits formed upon the land, I shall next consider the

including of the same in deposits formed under water.

It will be convenient to divide this branch of our subject into three

parts; considering, first, the various modes whereby the relics of

_terrestrial_ species may be buried in subaqueous formations; secondly,

the modes whereby animals and plants inhabiting _fresh water_ may be so

entombed; thirdly, how _marine_ species may become preserved in new

strata.

The phenomena above enumerated demand a fuller share of attention than

those previously examined, since the deposits which originate upon dry

land are insignificant in thickness, superficial extent, and durability,

when contrasted with those of subaqueous origin. At the same time, the

study of the latter is beset with greater difficulties; for we are here

concerned with the results of processes much farther removed from the

sphere of ordinary observation. There is, indeed, no circumstance which

so seriously impedes the acquisition of just views in our science as an

habitual disregard of the important fact, that the reproductive effects

of the principal agents of change are confined to another element--to

that larger portion of the globe, from which by our very organization we

are almost entirely excluded.[1059]

_Imbedding of Terrestrial Plants._

When a tree falls into a river from the undermining of the banks or from

being washed in by a torrent or flood, it floats on the surface, not

because the woody portion is specifically lighter than water, but

because it is full of pores containing air. When soaked for a

considerable time, the water makes its way into these pores, and the

wood becomes _waterlogged_ and sinks. The time required for this

process varies in different woods; but several kinds may be drifted to

great distances, sometimes across the ocean, before they lose their

buoyancy.

_Wood sunk to a great depth in the sea._--If wood be sunk to vast depths

in the sea, it may be impregnated with water suddenly. Captain Scoresby

informs us, in his Account of the Arctic Regions, that on one occasion a

whale, on being harpooned, ran out all the lines in the boat, which it

then dragged under water, to the depth of several thousand feet, the men

having just time to escape to a piece of ice. When the fish returned to

the surface "to blow," it was struck a second time, and soon afterwards

killed. The moment it expired it began to sink,--an unusual

circumstance, which was found to be caused by the weight of the sunken

boat, which still remained attached to it. By means of harpoons and

ropes the fish was prevented from sinking, until it was released from

the weight by connecting a rope to the lines of the attached boat, which

was no sooner done than the fish rose again to the surface. The sunken

boat was then hauled up with great labor; for so heavy was it, that

although before the accident it would have been buoyant when full of

water, yet it now required a boat at each end to keep it from sinking.

"When it was hoisted into the ship, the paint came off the wood in large

sheets; and the planks, which were of wainscot, were as completely

soaked in every pore as if they had lain at the bottom of the sea since

the flood! A wooden apparatus that accompanied the boat in its progress

through the deep, consisting chiefly of a piece of thick deal, about

fifteen inches square, happened to fall overboard, and, though it

originally consisted of the lightest fir, sank in the water like a

stone. The boat was rendered useless; even the wood of which it was

built, on being offered to the cook for fuel, was tried and rejected as

incombustible."[1060]

Captain Scoresby found that, by sinking pieces of fir, elm, ash, &c., to

the depth of four thousand and sometimes six thousand feet, they became

impregnated with sea-water, and when drawn up again, after immersion for

an hour, would no longer float. The effect of this impregnation was to

increase the dimensions as well as the specific gravity of the wood,

every solid inch having increased one-twentieth in size and twenty-one

twenty-fifths in weight.[1061]

_Drift-wood of the Mackenzie River._--When timber is drifted down by a

river, it is often arrested by lakes; and, becoming water-logged, it may

sink and be imbedded in lacustrine strata, if any be there forming;

sometimes a portion floats on till it reaches the sea. In the course of

the Mackenzie River we have an example of vast accumulations of

vegetable matter now in progress under both these circumstances.