The study of organic fossils was first pursued with connexion and

system in Italy. The hills which on each side skirt the

mountain-range of the Apennines are singularly rich in remains of

marine animals. When these remarkable objects drew the attention of

thoughtful men, controversies soon arose whether they really were

the remains of living creatures, or the productions of some

capricious or mysterious power by which the forms of such creatures

were mimicked; and again, if the shells were really the spoils of

the sea, whether they had been carried to the hills by the deluge of

which the Scripture speaks, or whether they indicated revolutions of

the earth of a different kind. The earlier works which contain the

descriptions of the phenomena have, in almost all instances, by far

the greater part of their pages occupied with these speculations;

indeed, the facts could not be studied without leading to such

inferences, and would not have been collected but for the interest

which such reasonings possessed. As one of the first persons who

applied a sound and vigorous intellect to these subjects, we may

notice the celebrated painter Leonardo da Vinci, whom we have

already had to refer to as one of the founders of the modern

mechanical sciences. He strenuously asserts the contents of the

rocks to be real shells, and maintains the reality of the changes of

the domain of land and sea which these spoils of the ocean imply.

"You will tell me," he says, "that nature and the influence of the

stars have formed these shelly forms in the mountains; then show me

a place in the mountains where the stars at the present day make

shelly forms of different ages, and of different species in the same

place. And how, with that, will you explain the gravel which is

hardened in stages at different heights in the mountains?" He then

mentions several other particulars respecting these evidences that

the existing mountains were formerly in the bed of the sea. Leonardo

died in 1519. At present we refer to geological essays like his,

only so far as they are descriptive. Going onwards with this view,

we may notice Fracastoro, who wrote concerning the petrifactions

which were brought to light in the mountains of Verona, when, in

1517, they were excavated for the purpose of repairing the city.

Little was done in the way of collection of facts for some time

after this. In 1669, Steno, a Dane resident in Italy, put forth his

treatise, _De Solido intra Solidum naturaliter contento_; and the

{508} following year, Augustino Scilla, a Sicilian painter,

published a Latin epistle, _De Corporibus Marinis Lapidescentibus_,

illustrated by good engravings of fossil-shells, teeth, and

corals.[8\18] After another interval of speculative controversy, we

come to Antonio Vallisneri, whose letters, _De' Corpi Marini che su'

Monti si trovano_, appeared at Venice in 1721. In these letters he

describes the fossils of Monte Bolca, and attempts to trace the

extent of the marine deposits of Italy,[9\18] and to distinguish the

most important of the fossils. Similar descriptions and figures were

published with reference to our own country at a later period. In

1766, Brander's _Fossilia Hantoniensia_, or Hampshire Fossils,

appeared; containing excellent figures of fossil shells from a part

of the south coast of England; and similar works came forth in other

parts of Europe.

[Note 8\18: Augustine Scilla's original drawings of fossil shells,

teeth, and corals, from which the engravings mentioned in the text

were executed, as well as the natural objects from which the

drawings were made, were bought by Woodward, and are now in the

Woodwardian Museum at Cambridge.]

[Note 9\18: p. 20.]

However exact might be the descriptions and figures thus produced,

they could not give such complete information as the objects

themselves, collected and permanently preserved in museums.

Vallisneri says,[10\18] that having begun to collect fossils for the

purpose of forming a grotto, he selected the best, and preserved

them "as a noble diversion for the more curious." The museum of

Calceolarius at Verona contained a celebrated collection of such

remains. A copious description of it appeared in 1622. Such

collections had been made from an earlier period, and catalogues of

them published. Thus Gessner's work, _De Rerum Fossilium, Lapidum et

Gemmarum Figuris_ (1565), contains a catalogue of the cabinet of

petrifactions collected by John Kentman; many catalogues of the same

kind appeared in the seventeenth century.[11\18] Lhwyd's

_**Lythophylacii Britannici Iconographia_, published at Oxford in

1669, and exhibiting a very ample catalogue of English Fossils

contained in the Ashmolean Museum, may be noticed as one of these.

[Note 10\18: p. 1.]

[Note 11\18: Parkinson, _Organic Remains_, vol. i. p. 20.]

One of the most remarkable occurrences in the progress of

descriptive geology in England, was the formation of a geological

museum by William Woodward as early as 1695. This collection, formed

with great labor, systematically arranged, and carefully catalogued,

he bequeathed to the University of Cambridge; founding and endowing

{509} at the same time a professorship of the study of geology. The

Woodwardian Museum still subsists, a monument of the sagacity with

which its author so early saw the importance of such a collection.

Collections and descriptions of fossils, including in the term

specimens of minerals of all kinds, as well as organic remains, were

frequently made, and especially in places where mining was

cultivated; but under such circumstances, they scarcely tended at

all to that general and complete knowledge of the earth of which we

are now tracing the progress.

In more modern times, collections may be said to be the most

important books of the geologist, at least next to the strata

themselves. The identifications and arrangements of our best

geologists, the immense studies of fossil anatomy by Cuvier and

others, have been conducted mainly by means of collections of

specimens. They are more important in this study than in botany,

because specimens which contain important geological information are

both more rare and more permanent. Plants, though each individual is

perishable, perpetuate and diffuse their kind; while the organic

impression on a stone, if lost, may never occur in a second

instance; but, on the other hand, if it be preserved in the museum,

the individual is almost as permanent in this case, as the species

in the other.

I shall proceed to notice another mode in which such information was

conveyed.

_Sect._ 3.--_First Construction of Geological Maps._

DR. LISTER, a learned physician, sent to the Royal Society, in 1683,

a proposal for maps of soils or minerals; in which he suggested that

in the map of England, for example, each soil and its boundaries

might be distinguished by color, or in some other way. Such a mode

of expressing and connecting our knowledge of the materials of the

earth was, perhaps, obvious, when the mass of knowledge became

considerable. In 1720, Fontenelle, in his observations on a paper of

De Reaumur's, which contained an account of a deposit of

fossil-shells in Touraine, says, that in order to reason on such

cases, "we must have a kind of geographical charts, constructed

according to the collection of shells found in the earth." But he

justly adds, "What a quantity of observations, and what time would

it not require to form such maps!"

The execution of such projects required, not merely great labor, but

{510} several steps in generalization and classification, before it

could take place. Still such attempts were made. In 1743, was

published, _A new Philosophico-chorographical Chart of East Kent,

invented and delineated_ by Christopher Packe, M.D.; in which,

however, the main object is rather to express the course of the

valleys than the materials of the country. Guettard formed the

project of a mineralogical map of France, and Monnet carried this

scheme into effect in 1780,[12\18] "by order of the king." In these

maps, however, the country is not considered as divided into soils,

still less strata; but each part is marked with its predominant

mineral only. The spirit of generalization which constitutes the

main value of such a work is wanting.

[Note 12\18: _Atlas et Description Minéralogique de la France,

entrepris par ordre du Roi_, par MM. Guettard et Monnet, Paris,

1780, pp. 212, with 31 maps.]

Geological maps belong strictly to Descriptive Geology; they are

free from those wide and doubtful speculations which form so large a

portion of the earlier geological books. Yet even geological maps

cannot be usefully or consistently constructed without considerable

steps of classification and generalization. When, in our own time,

geologists were become weary of controversies respecting theory,

they applied themselves with extraordinary zeal to the construction

of stratigraphical maps of various countries; flattering themselves

that in this way they were merely recording incontestable facts and

differences. Nor do I mean to intimate that their facts were

doubtful, or their distinctions arbitrary. But still they were facts

interpreted, associated, and represented, by means of the

classifications and general laws which earlier geologists had

established; and thus even Descriptive Geology has been brought into

existence as a science by the formation of systems and the discovery

of principles. At this we cannot be surprized, when we recollect the

many steps which the formation of Classificatory Botany required. We

must now notice some of the discoveries which tended to the

formation of Systematic Descriptive Geology. {511}

CHAPTER II.

FORMATION OF SYSTEMATIC DESCRIPTIVE GEOLOGY.

_Sect._ 1.--_Discovery of the Order and Stratification of the

Materials of the Earth._

THAT the substances of which the earth is framed are not scattered

and mixed at random, but possess identity and continuity to a

considerable extent, Lister was aware, when he proposed his map. But

there is, in his suggestions, nothing relating to stratification;

nor any order of position, still less of time, assigned to these

materials. Woodward, however, appears to have been fully aware of

the general law of stratification. On collecting information from

all parts, "the result was," he says, "that in time I was abundantly

assured that the circumstances of these things in remoter countries

were much the same with those of ours here: that the stone, and

other terrestrial matter in France, Flanders, Holland, Spain, Italy,

Germany, Denmark, and Sweden, was distinguished into _strata or

layers_, as it is in England; that these strata were divided by

parallel fissures; that there were enclosed in the stone and all the

other denser kinds of terrestrial matter, great numbers of the

shells, and other productions of the sea, in the same manner as in

that of this island."[13\18] So remarkable a truth, thus collected

from a copious collection of particulars by a patient induction, was

an important step in the science.

[Note 13\18: _Natural History of the Earth_, 1723.]

These general facts now began to be commonly recognized, and followed

into detail. **Stukeley the antiquary[14\18] (1724), remarked an

important feature in the strata of England, that their _escarpments_,

or steepest sides, are turned towards the west and north-west; and

Strachey[15\18] (1719), gave a stratigraphical description of certain

coal-mines near Bath.[16\18] Michell, appointed Woodwardian Professor

at Cambridge {512} in 1762, described this stratified structure of the

earth far more distinctly than his predecessors, and pointed out, as

the consequence of it, that "the same kinds of earths, stones, and

minerals, will appear at the surface of the earth in long parallel

slips, parallel to the long ridges of mountains; and so, in fact, we

find them."[17\18]

[Note 14\18: _Itinerarium Curiosum_, 1724.]

[Note 15\18: _Phil. Trans._ 1719, and _Observations on Strata, &c._

1729.]

[Note 16\18: Fitton, _Annals of Philosophy_, N. S. vol. i. and ii.

(1832, '3), p. 157.]

[Note 17\18: _Phil. Trans._ 1760.]

Michell (as appeared by papers of his which were examined after his

death) had made himself acquainted with the series of English strata

which thus occur from Cambridge to York;--that is, from the chalk to

the coal. These relations of position required that geological maps,

to complete the information they conveyed, should be accompanied by

geological _Sections_, or imaginary representations of the order and

mode of superpositions, as well as of the superficial extent of the

strata, as in more recent times has usually been done. The strata,

as we travel from the higher to the lower, come from under each

other into view; and this _out-cropping_, _basseting_, or by

whatever other term it is described, is an important feature in

their description.

It was further noticed that these relations of position were

combined with other important facts, which irresistibly suggested

the notion of a relation in time. This, indeed, was implied in all

theories of the earth; but observations of the facts most require

our notice. Steno is asserted by Humboldt[18\18] to be the first who

(in 1669) distinguished between rocks anterior to the existence of

plants and animals upon the globe, containing therefore no organic

remains; and rocks super-imposed on these, and full of such remains;

"turbidi maris sedimenta sibi invicem imposita".

[Note 18\18: _Essai **Géognostique_.]

Rouelle is stated, by his pupil Desmarest, to have made some

additional and important observations. "He saw," it is said, "that

the shells which occur in rocks were not the same in all countries;

that certain species occur together, while others do not occur in

the same beds; that there is a constant order in the arrangement of

these shells, certain species lying in distinct bands."[19\18]

[Note 19\18: _Encycl. Méthod. Geogr. Phys._ tom. i. p. 416, as

quoted by Fitton as above, p. 159.]

Such divisions as these required to be marked by technical names. A

distinction was made of _l'ancienne terre_ and _la nouvelle terre_,

to which Rouelle added a _travaille intermédiaire_. Rouelle died in

1770, having been known by lectures, not by books. Lehman, in 1756,

claims for himself the credit of being the first to observe and

describe correctly the structure of stratified countries; being

ignorant, {513} probably, of the labors of Strachey in England. He

divided mountains into three classes;[20\18] _primitive_, which were

formed with the world;--those which resulted from a partial

destruction of the primitive rocks;--and a third class resulting

from local or universal deluges. In 1759, also, Arduine,[21\18] in

his Memoirs on the mountains of Padua, Vicenza, and Verona, deduced,

from original observations, the distinction of rocks into _primary_,

_secondary_, and _tertiary_.

[Note 20\18: Lyell, i. 70.]

[Note 21\18: Ib. 72.]

The relations of position and fossils were, from this period,

inseparably connected with opinions concerning succession in time.

Odoardi remarked,[22\18] that the strata of the **Sub-Apennine hills

are _unconformable_ to those of the Apennine, (as Strachey had

observed, that the strata above the coal were unconformable to the

coal;[23\18]) and his work contained a clear argument respecting the

different ages of these two classes of hills. Fuchsel was, in 1762,

aware of the distinctness of strata of different ages in Germany.

Pallas and Saussure were guided by general views of the same kind in

observing the countries which they visited: but, perhaps, the

general circulation of such notions was most due to Werner.

[Note 22\18: Ib. 74.]

[Note 23\18: Fitton, p. 157.]

_Sect._ 2.--_Systematic form given to Descriptive Geology.--Werner._

WERNER expressed the general relations of the strata of the earth by

means of classifications which, so far as general applicability is

concerned, are extremely imperfect and arbitrary; he promulgated a

theory which almost entirely neglected all the facts previously

discovered respecting the grouping of fossils,--which was founded

upon observations made in a very limited district of Germany,--and

which was contradicted even by the facts of this district. Yet the

acuteness of his discrimination in the subjects which he studied,

the generality of the tenets he asserted, and the charm which he

threw about his speculations, gave to Geology, or, as he termed it,

_Geognosy_, a popularity and reputation which it had never before

possessed. His system had asserted certain universal formations,

which followed each other in a constant order;--granite the

lowest,--then mica-slate and clay-slate;--upon these _primitive_

rocks, generally highly inclined, rest other _transition_

strata;--upon these, lie _secondary_ ones, which being more nearly

horizontal, are called _flötz_ or flat. The term _formation_, {514}

which we have thus introduced, indicating groups which, by evidence

of all kinds,--of their materials, their position, and their organic

contents,--are judged to belong to the same period, implies no small

amount of theory: yet this term, from this time forth, is to be

looked upon as a term of classification solely, so far as

classification can be separately attended to.

Werner's distinctions of strata were for the most part drawn from

mineralogical constitution. Doubtless, he could not fail to perceive

the great importance of organic fossils. "I was witness," says M. de

Humboldt, one of his most philosophical followers, "of the lively

satisfaction which he felt when, in 1792, M. de **Schlottheim, one of

the most distinguished geologists of the school of Freiberg, began

to make the relations of fossils to strata the principal object of

his studies." But Werner and the disciples of his school, even the

most enlightened of them, never employed the characters derived from

organic remains with the same boldness and perseverance as those who

had from the first considered them as the leading phenomena: thus M.

de Humboldt expresses doubts which perhaps many other geologists do

not feel when, in 1823, he says, "Are we justified in concluding

that all formations are characterized by particular species? that

the fossil-shells of the chalk, the muschelkalk, the Jura limestone,

and the Alpine limestone, are all different? I think this would be

pushing the induction much too far."[24\18] In Prof. Jamieson's

_Geognosy_, which may be taken as a representation of the Wernerian

doctrines, organic fossils are in no instance referred to as

characters of formations or strata. After the curious and important

evidence, contained in organic fossils, which had been brought into

view by the labors of Italian, English, and German writers, the

promulgation of a system of Descriptive Geology, in which all this

evidence was neglected, cannot be considered otherwise than as a

retrograde step in science.

[Note 24\18: _Gissement des Roches_, p. 41.]

Werner maintained the aqueous deposition of all strata above the

primitive rocks; even of those _trap_ rocks, to which, from their

resemblance to lava and other phenomena, Raspe, Arduino, and others,

had already assigned a volcanic origin. The fierce and long

controversy between the _Vulcanists_ and _Neptunists_, which this

dogma excited, does not belong to this part of our history; but the

discovery of veins of granite penetrating the superincumbent slate,

to which the controversy led, was an important event in descriptive

geology. Hutton, the {515} author of the theory of igneous causation

which was in this country opposed to that of Werner, sought and

found this phenomenon in the Grampian hills, in 1785. This supposed

verification of his system "filled him with delight, and called

forth such marks of joy and exultation, that the guides who

accompanied him were persuaded, says his biographer,[25\18] that he

must have discovered a vein of silver or gold."[26\18]

[Note 25\18: Playfair's _Works_, vol. iv. p. 75.]

[Note 26\18: Lyell, i. 90.]

Desmarest's examination of Auvergne (1768) showed that there was

there an instance of a country which could not even be described

without terms implying that the basalt, which covered so large a

portion of it, had flowed from the craters of extinct volcanoes. His

map of Auvergne was an excellent example of a survey of such a

country, thus exhibiting features quite different from those of

common stratified countries.[27\18]

[Note 27\18: Lyell, i. 86.]

The facts connected with metalliferous veins were also objects of

Werner's attention. A knowledge of such facts is valuable to the

geologist as well as to the miner, although even yet much difficulty

attends all attempts to theorize concerning them. The facts of this

nature have been collected in great abundance in all mining

districts; and form a prominent part of the descriptive geology of

such districts; as, for example, the Hartz, and Cornwall.

Without further pursuing the history of the knowledge of the

inorganic phenomena of the earth, I turn to a still richer

department of geology, which is concerned with organic fossils.

_Sect._ 3.--_Application of Organic Remains as a Geological

Character.--Smith._

ROUELLE and Odoardi had perceived, as we have seen, that fossils

were grouped in bands: but from this general observation to the

execution of a survey of a large kingdom, founded upon this

principle, would have been a vast stride, even if the author of it

had been aware of the doctrines thus asserted by these writers. In

fact, however, William Smith executed such a survey of England, with

no other guide or help than his own sagacity and perseverance. In

his employments as a civil engineer, he noticed the remarkable

continuity and constant order of the strata in the neighborhood of

Bath, as discriminated by their fossils; and about the year 1793,

he[28\18] drew up a Tabular View of the {516} strata of that

district, which contained the germ of his subsequent discoveries.

Finding in the north of England the same strata and associations of

strata with which he had become acquainted in the west, he was led

to name them and to represent them by means of maps, according to

their occurrence over the whole face of England. These maps

appeared[29\18] in 1815; and a work by the same author, entitled

_The English Strata identified by Organic Remains_, came forth

later. But the views on which this identification of strata rests,

belong to a considerably earlier date; and had not only been acted

upon, but freely imparted in conversation many years before.

[Note 28\18: Fitton, p. 148.]

[Note 29\18: Brit. Assoc. 1832. Conybeare, p. 373.]

In the meantime the study of fossils was pursued with zeal in

various countries. Lamarck and Defrance employed themselves in

determining the fossil shells of the neighborhood of Paris;[30\18]

and the interest inspired by this subject was strongly nourished and

stimulated by the memorable work of Cuvier and Brongniart, _On the

Environs of Paris_, published in 1811, and by Cuvier's subsequent

researches on the subjects thus brought under notice. For now, not

only the distinction, succession, and arrangement, but many other

relations among fossil strata, irresistibly arrested the attention

of the philosopher. Brongniart[31\18] showed that very striking

resemblances occurred in their fossil remains, between certain

strata of Europe and of North America; and proved that a rock may be

so much disguised, that the identity of the stratum can only be

recognized by geological characters.[32\18]

[Note 30\18: Humboldt, _Giss. d. R._ p. 35.]

[Note 31\18: _Hist. Nat. des Crustacés Fossiles_, pp. 57, 62.]

[Note 32\18: Humboldt, _Giss. d. R._ p. 45.]

The Italian geologists had found in their hills, for the most part,

the same species of shells which existed in their seas; but the

German and English writers, as Gesner,[33\18] Raspe,[34\18] and

Brander,[35\18] had perceived that the fossil-shells were either of

unknown species, or of such as lived in distant latitudes. To decide

that the animals and plants, of which we find the remains in a

fossil state, were of species now extinct, obviously required an

exact and extensive knowledge of natural history. And if this were

so, to assign the relations of the past to the existing tribes of

beings, and the peculiarities of their vital processes and habits,

were tasks which could not be performed without the most consummate

physiological skill and talent. Such tasks, however, have been the

familiar employments of geologists, and naturalists incited and

{517} appealed to by geologists, ever since Cuvier published his

examination of the fossil inhabitants of the Paris basin. Without

attempting a history of such labors, I may notice a few

circumstances connected with them.

[Note 33\18: Lyell, i. 70.]

[Note 34\18: Ib. 74.]

[Note 35\18: Ib. 76.]

_Sect._ 4.--_Advances in Palæontology.--Cuvier._

SO long as the organic fossils which were found in the strata of the

earth were the remains of marine animals, it was very difficult for

geologists to be assured that the animals were such as did not exist

in any part or clime of the existing ocean. But when large land and

river animals were discovered, different from any known species, the

persuasion that they were of extinct races was forced upon the

naturalist. Yet this opinion was not taken up slightly, nor

acquiesced in without many struggles.

Bones supposed to belong to fossil elephants, were some of the first

with regard to which this conclusion was established. Such remains

occur in vast numbers in the soil and gravel of almost every part of

the world; especially in Siberia, where they are called the bones of

the _mammoth_. They had been noticed by the ancients, as we learn

from Pliny;[36\18] and had been ascribed to human giants, to

elephants imported by the Romans, and to many other origins. But in

1796, Cuvier had examined these opinions with a more profound

knowledge than his predecessors; and he thus stated the result of

his researches.[37\18] "With regard to what have been called the

fossil remains of elephants, from Tentzelius to Pallas, I believe

that I am in the condition to prove, that they belong to animals

which were very clearly different in species from our existing

elephants, although they resembled them sufficiently to be

considered as belonging to the same genera." He had founded this

conclusion principally on the structure of the teeth, which he found

to differ in the Asiatic and African elephant; while, in the fossil

animal, it was different from both. But he also reasoned in part on

the form of the skull, of which the best-known example had been

described in the _Philosophical Transactions_ as early as

1737.[38\18] "As soon," says Cuvier, at a later period, "as I became

acquainted with Messerschmidt's drawing, and joined to the

differences which it presented, those which I had myself observed in

the inferior jaw and the {518} molar teeth, I no longer doubted that

the fossil elephants were of a species different from the Indian

elephant. This idea, which I announced to the Institute in the month

of January, 1796, opened to me views entirely new respecting the

theory of the earth; and determined me to devote myself to the long

researches and to the assiduous labors which have now occupied me

for twenty-five years."[39\18]

[Note 36\18: _Hist. Nat._ lib. xxxvi. 18.]

[Note 37\18: _Mém. Inst. Math. et Phys._ tom. ii. p. 4.]

[Note 38\18: Described by Breyne from a specimen found in Siberia by

Messerschmidt in 1722. _Phil. Trans._ xl. 446.]

[Note 39\18: _Ossemens Fossiles_, second edit. i. 178.]

We have here, then, the starting-point of those researches

concerning extinct animals, which, ever since that time, have

attracted so large a share of notice from geologists and from the

world. Cuvier could hardly have anticipated the vast storehouse of

materials which lay under his feet, ready to supply him occupation

of the most intense interest in the career on which he had thus

entered. The examination of the strata on which Paris stands, and of

which its buildings consist, supplied him with animals, not only

different from existing ones, but some of them of great size and

curious peculiarities. A careful examination of the remains which

these strata contain was undertaken soon after the period we have

referred to. In 1802, Defrance had collected several hundreds of

undescribed species of shells; and Lamarck[40\18] began a series of

Memoirs upon them; remodelling the whole of Conchology, in order

that they might be included in its classifications. And two years

afterwards (1804) appears the first of Cuvier's grand series of

Memoirs containing the restoration of the vertebrate animals of

these strata. In this vast natural museum, and in contributions from

other parts of the globe, he discovered the most extraordinary

creatures:--the Palæotherium,[41\18] which is intermediate between

the horse and the pig; the Anoplotherium, which stands nearest to

the rhinoceros and the tapir; the Megalonix and Megatherium, animals

of the sloth tribe, but of the size of the ox and the rhinoceros.

The Memoirs which contained these and many other discoveries, set

the naturalists to work in every part of Europe.

[Note 40\18: _Annales du Muséum d'Hist. Nat._ tom. i. p. 308, and

the following volumes.]

[Note 41\18: Daubuisson, ii. 411.]

Another very curious class of animals was brought to light

principally by the geologists of England; animals of which the

bones, found in the _lias_ stratum, were at first supposed to be

those of crocodiles. But in 1816,[42\18] Sir Everard Home says, "In

truth, on a consideration of this skeleton, we cannot but be

inclined to believe, that among the animals destroyed by the

catastrophes of remote antiquity, there had {519} been some at least

that differ so entirely in their structure from any which now exist

as to make it impossible to arrange their fossil remains with any

known class of animals." The animal thus referred to, being clearly

intermediate between fishes and lizards, was named by Mr. König,

_Ichthyosaurus_; and its structure and constitution were more

precisely determined by Mr. Conybeare in 1821, when he had occasion

to compare with it another extinct animal of which he and Mr. de la

Beche had collected the remains. This animal, still more nearly

approaching the lizard tribe, was by Mr. Conybeare called

_Plesiosaurus_.[43\18] Of each of these two genera several species

were afterwards found.

[Note 42\18: _Phil. Trans._ 1816, p. 20.]

[Note 43\18: _Geol. Trans._ vol. v.]

Before this time, the differences of the races of animals and plants

belonging to the past and the present periods of the earth's

history, had become a leading subject of speculation among

geological naturalists. The science produced by this study of the

natural history of former states of the earth has been termed

_Palæontology_; and there is no branch of human knowledge more

fitted to stir men's wonder, or to excite them to the widest

physiological speculations. But in the present part of our history

this science requires our notice, only so far as it aims at the

restoration of the types of ancient animals, on clear and undoubted

principles of comparative anatomy. To show how extensive and how

conclusive is the science when thus directed, we need only refer to

Cuvier's _Ossemens Fossiles_;[44\18] a work of vast labor and

profound knowledge, which has opened wide the doors of this part of

geology. I do not here attempt even to mention the labors of the

many other eminent contributors to Palæontology; as Brocchi, Des

Hayes, Sowerby, Goldfuss, Agassiz, who have employed themselves on

animals, and Schlottheim, Brongniart, Hutton, Lindley, on plants.

[Note 44\18: The first edition appeared in 1812, consisting

principally of the Memoirs to which reference has already been made.]

[2nd Ed.] [Among the many valuable contributions to Palæontology in

more recent times, I may especially mention Mr. Owen's _Reports on

British Fossil Reptiles_, _on British Fossil Mammalia_, and _on the

Extinct Animals of Australia_, with descriptions of certain Fossils

indicative of large Marsupial Pachydermata: and M. Agassiz's _Report

on the Fossil Fishes of the Devonian System_, his _Synoptical Table

of British Fossil Fishes_, and his _Report on the Fishes of the

London Clay_. All these are contained in the volumes produced by the

British Association from 1839 to 1845. {520}

A new and most important instrument of palæontological investigation

has been put in the geologist's hand by Prof. Owen's discovery, that

the internal structure of teeth, as disclosed by the microscope, is

a means of determining the kind of the animal. He has carried into

every part of the animal kingdom an examination founded upon this

discovery, and has published the results of this in his

_Odontography_. As an example of the application of this character

of animals, I may mention that a tooth brought from Riga by Sir R.

Murchison was in this way ascertained by Mr. Owen to belong to a

fish of the genus _Dendrodus_. (_Geology of Russia_, i. 67.)]

When it had thus been established, that the strata of the earth are

characterized by innumerable remains of the organized beings which

formerly inhabited it, and that anatomical and physiological

considerations must be carefully and skilfully applied in order

rightly to interpret these characters, the geologist and the

palæontologist obviously had, brought before them, many very wide

and striking questions. Of these we may give some instances; but, in

the first place, we may add a few words concerning those eminent

philosophers to whom the science owed the basis on which succeeding

speculations were to be built.

_Sect._ 5.--_Intellectual Characters of the Founders of Systematic

Descriptive Geology._

IT would be in accordance with the course we have pursued in

treating of other subjects, that we should attempt to point out in

the founders of the science now under consideration, those

intellectual qualities and habits to which we ascribe their success.

The very recent date of the generalizations of geology, which has

hardly allowed us time to distinguish the calm expression of the

opinion of the wisest judges, might, in this instance, relieve us

from such a duty; but since our plan appears to suggest it, we will,

at least, endeavor to mark the characters of the founders of

geology, by a few of their prominent lines.

The three persons who must be looked upon as the main authors of

geological classification are, Werner, Smith, and Cuvier. These

three men were of very different mental constitution; and it will,

perhaps, not be difficult to compare them, in reference to those

qualities which we have all along represented as the main features

of the discoverer's genius, clearness of ideas, the possession of

numerous facts, and the power of bringing these two elements into

contact. {521}

In the German, considering him as a geologist, the ideal element

predominated. That Werner's powers of external discrimination were

extremely acute, we have seen in speaking of him as a mineralogist;

and his talent and tendency for classifying were, in his

mineralogical studies, fully fed by an abundant store of

observation; but when he came to apply this methodizing power to

geology, the love of system, so fostered, appears to have been too

strong for the collection of facts he had to deal with. As we have

already said, he promulgated, as representing the world, a scheme

collected from a province, and even too hastily gathered from that

narrow field. Yet his intense spirit of method in some measure

compensated for other deficiencies, and enabled him to give the

character of a science to what had been before a collection of

miscellaneous phenomena. The ardor of system-making produced a sort

of fusion, which, however superficial, served to bind together the

mass of incoherent and mixed materials, and thus to form, though by

strange and anomalous means, a structure of no small strength and

durability, like the ancient vitrified structures which we find in

some of our mountain regions.

Of a very different temper and character was William Smith. No

literary cultivation of his youth awoke in him the speculative love

of symmetry and system; but a singular clearness and precision of

the classifying power, which he possessed as a native talent, was

exercised and developed by exactly those geological facts among

which his philosophical task lay. Some of the advances which he

made, had, as we have seen, been at least entered upon by others who

preceded him: but of all this he was ignorant; and, perhaps, went on

more steadily and eagerly to work out his own ideas, from the

persuasion that they were entirely his own. At a later period of his

life, he himself published an account of the views which had

animated him in his earlier progress. In this account[45\18] he

dates his attempts to discriminate and connect strata from the year

1790, at which time he was twenty years old. In 1792, he "had

considered how he could best represent the order of

superposition--continuity of course--and general eastern declination

of the strata." Soon after, doubts which had arisen were removed by

the "discovery of a mode of identifying the strata by the organized

fossils respectively imbedded therein." And "thus stored with

ideas," as he expresses himself, he began to communicate them to his

friends. In all this, we see great vividness {522} of thought and

activity of mind, unfolding itself exactly in proportion to the

facts with which it had to deal. We are reminded of that cyclopean

architecture in which each stone, as it occurs, is, with wonderful

ingenuity, and with the least possible alteration of its form,

shaped so as to fit its place in a solid and lasting edifice.

[Note 45\18: _Phil. Mag._ 1833, vol. i. p. 38.]

Different yet again was the character (as a geological discoverer)

of the great naturalist of the beginning of the nineteenth century.

In that part of his labors of which we have now to speak, Cuvier's

dominant ideas were rather physiological than geological. In his

views of past physical changes, he did not seek to include any

ranges of facts which lay much beyond the narrow field of the Paris

basin. But his sagacity in applying his own great principle of the

Conditions of Existence, gave him a peculiar and unparalleled power

in interpreting the most imperfect fossil records of extinct

anatomy. In the constitution of his mind, all philosophical

endowments were so admirably developed and disciplined, that it was

difficult to say, whether more of his power was due to genius or to

culture. The talent of classifying which he exercised in geology,

was the result of the most complete knowledge and skill in zoology;

while his views concerning the revolutions which had taken place in

the organic and inorganic world, were in no small degree aided by an

extraordinary command of historical and other literature. His

guiding ideas had been formed, his facts had been studied, by the

assistance of all the sciences which could be made to bear upon

them. In his geological labors we seem to see some beautiful temple,

not only firm and fair in itself, but decorated with sculpture and

painting, and rich in all that art and labor, memory and

imagination, can contribute to its beauty.

[2nd Ed.] [Sir Charles Lyell (B. i. c. iv.) has quoted with approval

what I have elsewhere said, that the advancement of three of the

main divisions of geology in the beginning of the present century

was promoted principally by the three great nations of Europe,--the

German, the English, and the French:--Mineralogical Geology by the

German school of Werner:--Secondary Geology by Smith and his English

successors;--Tertiary Geology by Cuvier and his fellow-laborers in

France.] {523}

CHAPTER III.

SEQUEL TO THE FORMATION OF SYSTEMATIC DESCRIPTIVE GEOLOGY.

_Sect._ 1.--_Reception and Diffusion of Systematic Geology._

IF our nearness to the time of the discoveries to which we have just

referred, embarrasses us in speaking of their authors, it makes it

still more difficult to narrate the reception with which these

discoveries met. Yet here we may notice a few facts which may not be

without their interest.

The impression which Werner made upon his hearers was very strong;

and, as we have already said, disciples were gathered to his school

from every country, and then went forward into all parts of the

world, animated by the views which they had caught from him. We may

say of him, as has been so wisely said of a philosopher of a very

different kind,[46\18] "He owed his influence to various causes; at

the head of which may be placed that genius for system, which,

though it cramps the growth of knowledge, perhaps finally atones for

that mischief by the zeal and activity which it rouses among

followers and opponents, who discover truth by accident, when in

pursuit of weapons for their warfare." The list of Werner's pupils

for a considerable period included most of the principal geologists

of Europe; Freisleben, Mohs, Esmark, d'Andrada, Raumer, Engelhart,

Charpentier, Brocchi. Alexander von Humboldt and Leopold von Buch

went forth from his school to observe America and Siberia, the Isles

of the Atlantic, and the coast of Norway. Professor Jameson

established at Edinburgh a Wernerian Society; and his lecture-room

became a second centre of Wernerian doctrines, whence proceeded many

zealous geological observers; among these we may mention as one of

the most distinguished, M. Ami Boué, though, like several others, he

soon cast away the peculiar opinions of the Wernerian school. The

classifications of this school were, however, diffused over the

civilized world with {524} extraordinary success; and were looked

upon with great respect, till the study of organic fossils threw

them into the shade.

[Note 46\18: Mackintosh _on Hobbes_, Dissert. p. 177.]

Smith, on the other hand, long pursued his own thoughts without aid

and without sympathy. About 1799 he became acquainted with a few

gentlemen (Dr. Anderson, Mr. Richardson, Mr. Townsend, and Mr.

Davies), who had already given some attention to organic fossils,

and who were astonished to find his knowledge so much more exact and

extensive than their own. From this time he conceived the intention

of publishing his discoveries; but the want of literary leisure and

habits long prevented him. His knowledge was orally communicated

without reserve to many persons; and thus gradually and insensibly

became part of the public stock. When this diffusion of his views

had gone on for some time, his friends began to complain that the

author of them was deprived of his well-merited share of fame. His

delay in publication made it difficult to remedy this wrong; for

soon after he published his Geological Map of England, another

appeared, founded upon separate observations; and though, perhaps,

not quite independent of his, yet in many respects much more

detailed and correct. Thus, though his general ideas obtained

universal currency, he did not assume his due prominence as a

geologist. In 1818, a generous attempt was made to direct a proper

degree of public gratitude to him, in an article in the _Edinburgh

Review_, the production of Dr. Fitton, a distinguished English

geologist. And when the eminent philosopher, Wollaston, had

bequeathed to the Geological Society of London a fund from which a

gold medal was to be awarded to geological services, the first of

such medals was, in 1831, "given to Mr. William Smith, in

consideration of his being a great original discoverer in English

geology; and especially for his having been the first in this

country to discover and to teach the identification of strata, and

to determine their succession by means of their imbedded fossils."

Cuvier's discoveries, on the other hand, both from the high

philosophic fame of their author, and from their intrinsic

importance, arrested at once the attention of scientific Europe;

and, notwithstanding the undoubted priority of Smith's labors, for a

long time were looked upon as the starting-point of our knowledge of

organic fossils. And, in reality, although Cuvier's memoirs derived

the greatest part of their value from his zoological conclusions,

they reflected back no small portion of interest on the

classifications of strata which were involved in his inferences. And

the views which he presented gave to geology an attractive and

striking character, and a connexion with {525} large physiological

as well as physical principles, which added incomparably to its

dignity and charm.

In tracing the reception and diffusion of doctrines such as those of

Smith and Cuvier, we ought not to omit to notice more especially the

formation and history of the Geological Society of London, just

mentioned. It was established in 1807, with a view to multiply and

record observations, and patiently to await the result of some

future period; that is, its founders resolved to apply themselves to

Descriptive Geology, thinking the time not come for that theoretical

geology which had then long fired the controversial ardor of

Neptunists and Plutonists. The first volume of the Transactions of

this society was published in 1811. The greater part of the contents

of this volume[47\18] savor of the notions of the Wernerian school;

and there are papers on some of the districts in England most rich

in fossils, which Mr. Conybeare says, well exhibit the low state of

secondary geology at that period. But a paper by Mr. Parkinson

refers to the discoveries both of Smith and of Cuvier; and in the

next volume, Mr. Webster gives an account of the Isle of Wight,

following the admirable model of Cuvier and Brongniart's account of

the Paris basin. "If we compare this memoir of Mr. Webster with the

preceding one of Dr. Berger (also of the Isle of Wight), they at

once show themselves to belong to two very distinct eras of science;

and it is difficult to believe that the interval which elapsed

between their respective publication was only three or four

years."[48\18]

[Note 47\18: Conybeare, _Report. Brit. Assoc._ p. 372.]

[Note 48\18: Conybeare, _Report_, p. 372.]

Among the events belonging to the diffusion of sound geological

views in this country, we may notice the publication of a little

volume entitled, _The Geology of England and Wales_, by Mr.

Conybeare and Mr. Phillips, in 1821; an event far more important

than, from the modest form and character of the work, it might at

first sight appear. By describing in detail the geological structure

and circumstances of England (at least as far downwards as the

coal), it enabled a very wide class of readers to understand and

verify the classifications which geology had then very recently

established; while the extensive knowledge and philosophical spirit

of Mr. Conybeare rendered it, under the guise of a topographical

enumeration, in reality a profound and instructive scientific

treatise. The vast impulse which it gave to the study of sound

descriptive geology was felt and acknowledged in other countries, as

well as in Britain. {526}

Since that period, Descriptive Geology in England has constantly

advanced. The advance has been due mainly to the labors of the members

of the Geological Society; on whose merits as cultivators of their

science, none but those who are themselves masters of the subject,

have a right to dwell. Yet some parts of the scientific character of

these men may be appreciated by the general speculator; for they have

shown that there are no talents and no endowments which may not find

their fitting employment in this science. Besides that they have

united laborious research and comprehensive views, acuteness and

learning, zeal and knowledge; the philosophical eloquence with which

they have conducted their discussions has had a most beneficial

influence on the tone of their speculations; and their researches in

the field, which have carried them into every country and every class

of society, have given them that prompt and liberal spirit, and that

open and cordial bearing, which results from intercourse with the

world on a large and unfettered scale. It is not too much to say, that

in our time, Practical Geology has been one of the best schools of

philosophical and general culture of mind.

_Sect._ 2.--_Application of Systematic Geology. Geological Surveys

and Maps._

SUCH surveys as that which Conybeare and Phillips's book presented

with respect to England, were not only a means of disseminating the

knowledge implied in the classifications of such a work, but they

were also an essential part of the Application and Extension of the

principles established by the founders of Systematic Geology. As

soon as the truth of such a system was generally acknowledged, the

persuasion of the propriety of geological surveys and maps of each

country could not but impress itself on men's minds.

When the earlier writers, as Lister and Fontenelle, spoke of

mineralogical and fossilological maps, they could hardly be said to

know the meaning of the terms which they thus used. But when

subsequent classifications had shown how such a suggestion might be

carried into effect, and to what important consequences it might

lead, the task was undertaken in various countries in a vigorous and

consistent manner. In England, besides Smith's map, another, drawn

up by Mr. Greenough, was published by the Geological Society in

1819; and, being founded on very numerous observations of the author

and his friends, made with great labor and cost, was not only an

important {527} correction and confirmation of Smith's labors, but a

valuable storehouse and standard of what had then been done in

English geology. Leopold von Buch had constructed a geological map

of a large portion of Germany, about the same period; but, aware of

the difficulty of the task he had thus attempted, he still forbore

to publish it. At a later period, and as materials accumulated, more

detailed maps of parts of Germany were produced by Hoffmann and

others. The French government entrusted to a distinguished Professor

of the School of Mines (M. Brochant de Villiers), the task of

constructing a map of France on the model of Mr. Greenough's;

associating with him two younger persons, selected for their energy

and talents, MM. Beaumont and Dufrénoy. We shall have occasion

hereafter to speak of the execution of this survey. By various

persons, geological maps of almost every country and province of

Europe, and of many parts of Asia and America, have been published.

I need not enumerate these, but I may refer to the account given of

them by Mr. Conybeare, in the _Reports of the British Association

for_ 1832, p. 384. These various essays may be considered as

contributions, though hitherto undoubtedly very imperfect ones, to

that at which Descriptive Geology ought to aim, and which is

requisite as a foundation for sound theory;--a complete geological

survey of the whole earth. But we must say a few words respecting

the language in which such a survey must be written.

As we have already said, that condition which made such maps and the

accompanying descriptions possible, was that the strata and their

contents had previously undergone classification and arrangement at

the hands of the fathers of geology. Classification, in this as in

other cases, implied names which should give to the classes

distinctness and permanence; and when the series of strata belonging

to one country were referred to in the description of another, in

which they appeared, as was usually the case, under an aspect at

least somewhat different, the supposed identification required a

peculiar study of each case; and thus Geology had arrived at the

point, which we have before had to notice as one of the stages of

the progress of Classificatory Botany, at which a technical

_nomenclature_ and a well-understood _synonymy_ were essential parts

of the science.

_Sect._ 3.--_Geological Nomenclature._

BY Nomenclature we mean a _system_ of names; and hence we can {528}

not speak of a Geological Nomenclature till we come to Werner and

Smith. The earlier mineralogists had employed names, often

artificial and arbitrary, for special minerals, but no technical and

constant names for strata. The elements of Werner's names for the

members of his geological series were words in use among miners, as

_Gneiss_, _Grauwacke_, _Thonschiefer_, _Rothe todte liegende_,

_Zechstein_; or arbitrary names of the mineralogists, as Syenite,

Serpentine, Porphyry, Granite. But the more technical part of his

phraseology was taken from that which is the worst kind of name,

arbitrary numeration. Thus he had his _first_ sandstone formation,

_second_ sandstone, _third_ sandstone; _first_ flötz limestone,

_second_ flötz limestone, _third_ flötz limestone. Such names are,

beyond all others, liable to mistake in their application, and

likely to be expelled by the progress of knowledge; and accordingly,

though the Wernerian names for rocks mineralogically distinguished,

have still some currency, his sandstones and limestones, after

creating endless confusion while his authority had any sway, have

utterly disappeared from good geological works.

The nomenclature of Smith was founded upon English provincial terms

of very barbarous aspect, as _Cornbrash_, _Lias_, _Gault_, _Clunch

Clay_, _Coral Rag_. Yet these terms were widely diffused when his

classification was generally accepted; they kept their place,

precisely because they had no systematic signification; and many of

them are at present part of the geological language of the whole

civilized world.

Another kind of names which has been very prevalent among geologists

are those borrowed from places. Thus the Wernerians spoke of Alpine

Limestone and Jura Limestone; the English, of Kimmeridge Clay and

Oxford Clay, Purbeck Marble, and Portland Rock. These names,

referring to the stratum of a known locality as a type, were good,

as far as an identity with that type had been traced; but when this

had been incompletely done, they were liable to great ambiguity. If

the Alps or the Jura contain several formations of limestone, such

terms as we have noticed, borrowed from those mountains, cease to be

necessarily definite, and may give rise to much confusion.

Descriptive names, although they might be supposed to be the best,

have, in fact, rarely been fortunate. The reason of this is

obvious;--the mark which has been selected for description may

easily fail to be essential; and the obvious connexions of natural

facts may overleap the arbitrary definition. As we have already

stated in the history of botany, the establishment of descriptive

marks of real classes presupposes the important but difficult step,

of the discovery of such marks. {529} Hence those descriptive names

only have been really useful in geology which had been used without

any scrupulous regard to the appropriateness of the description. The

_Green Sand_ may be white, brown, or red; the _Mountain Limestone_

may occur only in valleys; the _Oolite_ may have no roe-like

structure; and yet these may be excellent geological names, if they

be applied to formations geologically identical with those which the

phrases originally designated. The signification may assist the

memory, but must not be allowed to subjugate the faculty of natural

classification.

The terms which have been formed by geologists in recent times have

been drawn from sources similar to those of the older ones, and will

have their fortune determined by the same conditions. Thus Mr. Lyell

has given to the divisions of the tertiary strata the appellations

_Pleiocene_, _Meiocene_, _Eocene_, accordingly as they contain a

_majority_ of recent species of shells, a _minority_ of such

species, or a small proportion of living species, which may be

looked upon as indicating the _dawn_ of the existing state of the

animate creation. But in this case, he wisely treats his

distinctions, not as definitions, but as the marks of natural

groups. "The plurality of species indicated by the name _pleiocene_

must not," he says,[49\18] "be understood to imply an absolute

majority of recent fossil shells in all cases, but a comparative

preponderance wherever the pleiocene are contrasted with strata of

the period immediately preceding."

[Note 49\18: _Geol._ iii. 392.]

Mr. Lyell might have added, that no precise percentage of recent

species, nor any numerical criterion whatever, can be allowed to

overbear the closer natural relations of strata, proved by evidence

of a superior kind, if such can be found. And this would be the

proper answer to the objection made by De la Beche to these names;

namely, that it may happen that the _meiocene_ rocks of one country

may be of the same date as the _pleiocene_ of another; the same

formation having in one place a majority, in another a minority, of

existing species. We are not to run into this incongruity, for we

are not so to apply the names. The formation which has been called

pleiocene, must continue to be so called, even where the majority of

recent species fails; and all rocks that agree with that in date,

without further reference to the numerical relations of their

fossils, must also share in the name.

To invent good names for these large divisions of the series of

strata is indeed extremely difficult. The term _Oolite_ is an

instance in which {530} a descriptive word has become permanent in a

case of this kind; and, in imitation of it, _Pœcilite_ (from

ποικίλος, various,**) has been proposed by Mr. Conybeare[50\18] as

a name for the group of strata inferior to the oolites, of which the

_Variegated_ Sandstone (Bunter Sandstein, Grès Bigarré,) is a

conspicuous member. For the series of formations which lies

immediately over the rocks in which no organic remains are found,

the term _Transition_ was long used, but with extreme ambiguity and

vagueness. When this series, or rather the upper part of it, was

well examined in South Wales, where it consists of many well-marked

members, and may be probably taken as a type for a large portion of

the rest of the world, it became necessary to give to the group thus

explored a name not necessarily leading to assumption or

controversy. Mr. Murchison selected the term _Silurian_, borrowed

from the former inhabitants of the country in which his types were

found; and this is a term excellent in many respects; but one which

will probably not quite supersede "Transition," because, in other

places, transition rocks occur which correspond to none of the

members of the Silurian region.

[Note 50\18: _Report_, p. 379.]

Though new names are inevitable accompaniments of new views of

classification, and though, therefore, the geological discoverer

must be allowed a right to coin them, this is a privilege which, for

the sake of his own credit, and the circulation of his tokens, he

must exercise with great temperance and judgment. M. Brongniart may

be taken as an example of the neglect of this caution. Acting upon

the principle, in itself a sound one, that inconveniences arise from

geological terms which have a mineralogical signification, he has

given an entirely new list of names of the members of the geological

series. Thus the primitive unstratified rocks are _terrains

agalysiens_; the transition semi-compact are _hemilysiens_; the

sedimentary strata are _yzemiens_; the diluvial deposits are

_clysmiens_; and these divisions are subdivided by designations

equally novel; thus of the "terrains yzemiens," members are--the

terrains _clastiques_, _tritoniens_, _protéïques_, _palæotheriens_,

_epilymniques_, _thalassiques_.[51\18] Such a nomenclature appears

to labor under great inconveniences, since the terms are descriptive

in their derivation, yet are not generally intelligible, and refer

to theoretical views yet have not the recommendation of systematic

connexion. {531}

[Note 51\18: Brongniart, _Tableau des Terrains_, 1829.]

_Sect._ 4.--_Geological Synonymy, or Determination of Geological

Equivalents._

IT will easily be supposed that with so many different sources of

names as we have mentioned, the same stratum may be called by

different designations; and thus a synonymy may be necessary for

geology; as it was for botany in the time of Bauhin, when the same

plants had been spoken of by so many different appellations in

different authors. But in reality, the synonymy of geology is a

still more important part of the subject than the analogy of botany

would lead us to suppose. For in plants, the species are really

fixed, and easily known when seen; and the ambiguity is only in the

imperfect communication or confused ideas of the observers. But in

geology, the identity of a stratum or formation in different places,

though not an arbitrary, may be a very doubtful matter, even to him

who has seen and examined. To assign its right character and place

to a stratum in a new country, is, in a great degree, to establish

the whole geological history of the country. To assume that the same

names may rightly be applied to the strata of different countries,

is to take for granted, not indeed the Wernerian dogma of universal

formations, but a considerable degree of generality and uniformity

in the known formations. And how far this generality and uniformity

prevail, observation alone can teach. The search for geological

synonyms in different countries brings before us two

questions;--first, _are_ there such synonyms? and only in the second

place, and as far as they occur, _what_ are they?

In fact, it is found that although formations which must be considered

as geologically identical (because otherwise no classification is

possible,) do extend over large regions, and pass from country to

country, their identity includes certain modifications; and the

determination of the identity and of the modifications are inseparably

involved with each other, and almost necessarily entangled with

theoretical considerations. And in two countries, in which we find

this modified coincidence, instead of saying that the strata are

identical, and that their designations are synonyms, we may, with more

propriety, consider them as two corresponding series; of which the

members of the one may be treated as the _Representatives_ or

_Equivalents_ of the members of the other.

This doctrine of Representatives or Equivalents supposes that the

geological phenomena in the two countries have been the results of

{532} similar series of events, which have, in some measure, coincided

in time and order; and thus, as we have said, refers us to a theory.

But yet, considered merely as a step in classification, the comparison

of the geological series of strata in different countries is, in the

highest degree, important and interesting. Indeed in the same manner

in which the separation of Classificatory from Chemical Mineralogy is

necessary for the completion of mineralogical science, the comparative

Classification of the strata of different countries according to their

resemblances and differences alone, is requisite as a basis for a

Theory of their causes. But, as will easily be imagined from its

nature, this part of descriptive geology deals with the most difficult

and the most elevated problems; and requires a rare union of laborious

observation with a comprehensive spirit of philosophical

classification.

In order to give instances of this process (for of the vast labor

and great talents which have been thus employed in England, France,

and Germany, it is only instances that we can give,) I may refer to

the geological survey of France, which was executed, as we have

already stated, by order of the government. In this undertaking it

was intended to obtain a knowledge of the whole mineral structure of

France; but no small portion of this knowledge was brought into

view, when a synonymy had been established between the Secondary

Rocks of France and the corresponding members of the English and

German series, which had been so well studied as to have become

classical points of standard reference. For the purpose of doing

this, the principal directors of the survey, MM. Brochant de

Villiers, De Beaumont, and Dufrénoy, came to England in 1822, and

following the steps of the best English geologists, in a few months

made themselves acquainted with the English series. They then

returned to France, and, starting from the chalk of Paris in various

directions, travelled on the lines which carried them over the edges

of the strata which emerge from beneath the chalk, identifying, as

they could, the strata with their foreign analogues. They thus

recognized almost all of the principal beds of the oolitic series of

England.[52\18] At the same time they found differences as well as

resemblances. Thus the Portland and Kimmeridge beds of France were

found to contain in abundance a certain shell, the _gryphæa

virgula_, which had not before been much remarked in those beds in

England. With regard to the synonyms in Germany, on the other hand,

a difference of opinion {538} arose between M. Elie de Beaumont and

M. Voltz,[53\18] the former considering the _Grès de Vosges_ as the

equivalent of the _Rothe todte liegende_, which occurs beneath the

Zechstein, while M. Voltz held that it was the lower portion of the

Red or _Variegated Sandstone_ which rests on the Zechstein.

[Note 52\18: De la Beche, _Manual_, 305.]

[Note 53\18: De la Beche, _Manual_, 381.]

In the same manner, from the first promulgation of the Wernerian

system, attempts were made to identify the English with the German

members of the geological alphabet; but it was long before this

alphabet was rightly read. Thus the English geologists who first

tried to apply the Wernerian series to this country, conceived the

Old and New Red Sandstone of England to be the same with the Old and

New Red Sandstone of Werner; whereas Werner's Old Red, the Rothe

todte liegende, is above the coal, while the English Old Red is

below it. This mistake led to a further erroneous identification of

our Mountain Limestone with Werner's First Flötz Limestone; and

caused an almost inextricable confusion, which, even at a recent

period, has perplexed the views of German geologists respecting this

country. Again, the Lias of England was, at first, supposed to be

the equivalent of the Muschelkalk of Germany. But the error of this

identification was brought into view by examinations and discussions

in which MM. Œyenhausen and Dechen took the lead; and at a later

period, Professor Sedgwick, by a laborious examination of the strata

of England, was enabled to show the true relation of this part of

the geology of the two countries. According to him, the New Red

Sandstone of England, considered as one great complex formation, may

be divided into seven members, composed of sandstones, limestones,

and marls; five of which represent respectively the _Rothe todte

liegende_; the _Kupfer schiefer_; the _Zechstein_, (with the

_Rauchwacké_, _Asche_, and _Stinkstein_ of the Thuringenwald;) the

_Bunter sandstein_; and the _Keuper_: while the _Muschelkalk_, which

lies between the two last members of the German list, has not yet

been discovered in our geological series. "Such a coincidence," he

observes,[54\18] "in the subdivisions of two distant mechanical

deposits, even upon the supposition of their being strictly

contemporaneous, is truly astonishing. It has not been assumed

hypothetically, but is the fair result of the facts which are

recorded in this paper."

[Note 54\18: _Geol. Trans._ Second Series, iii. 121.]

As an example in which the study of geological equivalents becomes

still more difficult, we may notice the attempts to refer the strata

of {534} the Alps to those of the north-west of Europe. The

dark-colored marbles and schists resembling mica slate[55\18] were,

during the prevalence of the Wernerian theory, referred, as was

natural, to the transition class. The striking physical characters

of this mountain region, and its long-standing celebrity as a

subject of mineralogical examination, made a complete subversion of

the received opinion respecting its place in the geological series,

an event of great importance in the history of the science. Yet this

was what occurred when Dr. Buckland, in 1820, threw his piercing

glance upon this district. He immediately pointed out that these

masses, by their fossils, approach to the Oolitic Series of this

country. From this view it followed, that the geological equivalents

of that series were to be found among rocks in which the

mineralogical characters were altogether different, and that the

loose limestones of England represent some of the highly-compact and

crystalline marbles of Italy and Greece. This view was confirmed by

subsequent investigations; and the correspondence was traced, not

only in the general body of the formations, but in the occurrence of

the Red Marl at its bottom, and the Green Sand and Chalk at its top.

[Note 55\18: De la Beche, _Manual_, 313.]

The talents and the knowledge which such tasks require are of no

ordinary kind; nor, even with a consummate acquaintance with the

well-ascertained formations, can the place of problematical strata

be decided without immense labor. Thus the examination and

delineation of hundreds of shells by the most skilful conchologists,

has been thought necessary in order to determine whether the

calcareous beds of Maestricht and of Gosau are or are not

intermediate, as to their organic contents, between the chalk and

the tertiary formations. And scarcely any point of geological

classification can be settled without a similar union of the

accomplished naturalist with the laborious geological collector.

It follows from the views already presented, of this part of geology,

that no attempt to apply to distant countries the names by which the

well-known European strata have been described, can be of any value,

if not accompanied by a corresponding attempt to show how far the

European series is really applicable. This must be borne in mind in

estimating the import of the geological accounts which have been given

of various parts of Asia, Africa, and America. For instance, when the

carboniferous group and the new red sandstone are stated to {535} be

found in India, we require to be assured that these formations are, in

some way, the equivalents of their synonyms in countries better

explored. Till this is done, the results of observation in such places

would be better conveyed by a nomenclature implying only those facts

of resemblance, difference, and order, which have been ascertained in

the country so described. We know that serious errors were incurred by

the attempts made to identify the Tertiary strata of other countries

with those first studied in the Paris basin. Fancied points of

resemblance, Mr. Lyell observes, were magnified into undue importance,

and essential differences in mineral character and organic contents

were slurred over.

[2nd Ed.] [The extension of geological surveys, the construction of

geological maps, and the determination of the geological equivalents

which replace each other in various countries, have been carried on

in continuation of the labors mentioned above, with enlarged

activity, range, and means. It is estimated that one-third of the

land of each hemisphere has been geologically explored; and that

thus Descriptive Geology has now been prosecuted so far, that it is

not likely that even the extension of it to the whole globe would

give any material novelty of aspect to Theoretical Geology. The

recent literature of the subject is so voluminous that it is

impossible for me to give any account of it here; very imperfectly

acquainted, as I am, even with the English portion, and still more,

with what has been produced in other countries.

While I admire the energetic and enlightened labors by which the

philosophers of France, Belgium, Germany, Italy, Russia, and

America, have promoted scientific geology, I may be allowed to

rejoice to see in the very phraseology of the subject, the evidence

that English geologists have not failed to contribute their share to

the latest advances in the science. The following order of strata

proceeding upwards is now, I think, recognized throughout Europe.

The _Silurian_; the _Devonian_ (Old Red Sandstone;) the

_Carboniferous_; the _Permian_, (Lower part of the new Red Sandstone

series;) the _Trias_, (Upper three members of the New Red Sandstone

series;) the _Lias_; the _Oolite_, (in which are reckoned by M.

D'Orbigny the Etages _Bathonien_, _Oxonien_, _Kimmeridgien_, and

_Portlandien_;) the _Neocomien_, (Lower Green Sand,) the Chalk; and

above these, Tertiary and Supra-Tertiary beds. Of these, the

Silurian, described by Sir R. Murchison from its types in South

Wales, has been traced by European Geologists through the Ardennes,

Servia, Turkey, the shores of the Gulf of Finland, the valley {536}

of the Mississippi, the west coast of North America, and the

mountains of South America. Again, the labors of Prof. Sedgwick and

Sir R. Murchison, in 1836, '7, and '8, aided by the sagacity of Mr.

Lonsdale, led to their placing certain rocks of Devon and Cornwall

as a formation intermediate between the Silurian and Carboniferous

Series; and the Devonian System thus established has been accepted

by geologists in general, and has been traced, not only in various

parts of Europe, but in Australia and Tasmania, and in the

neighborhood of the Alleganies.

Above the Carboniferous Series, Sir R. Murchison and his fellow

laborers, M. de Verneuil and Count Keyserling, have found in Russia

a well-developed series of rocks occupying the ancient kingdom of

Permia, which they have hence called the _Permian formation_; and

this term also has found general acceptance. The next group, the

Keuper, Muschelkalk, and Bunter Sandstein of Germany, has been

termed _Trias_ by the continental geologists. The _Neocomien_ is

called from Neuchatel, where it is largely developed. Below all

these rocks come, in England, the _Cambrian_ on which Prof. Sedgwick

has expended so many years of valuable labor. The comparison of the

Protozoic and Hypozoic rocks of different countries is probably

still incomplete.

The geologists of North America have made great progress in

decyphering and describing the structure of their own country; and

they have wisely gone, in a great measure, upon the plan which I

have commended at the end of the third Chapter;--they have compared

the rocks of their own country with each other, and given to the

different beds and formations names borrowed from their own

localities. This course will facilitate rather than impede the

redaction of their classification to its synonyms and equivalents in

the old world.

Of course it is not to be expected nor desired that books belonging

to Descriptive Geology shall exclude the other two branches of the

subject, Geological Dynamics and Physical Geology. On the contrary,

among the most valuable contributions to both these departments have

been speculations appended to descriptive works. And this is

naturally and rightly more and more the case as the description

embraces a wider field. The noble work _On the Geology of Russia and

the Urals_, by Sir Roderick Murchison and his companions, is a great

example of this, as of other merits in a geological book. The author

introduces into his pages the various portions of geological

dynamics of which I shall have to speak afterwards; and thus

endeavors to make out the {537} physical history of the region, the

boundaries of its raised sea bottoms, the shores of the great

continent on which the mammoths lived, the period when the gold ore

was formed, and when the watershed of the Ural chain was elevated.]

CHAPTER IV.

ATTEMPTS TO DISCOVER GENERAL LAWS IN GEOLOGY.

_Sect._ 1.--_General Geological Phenomena._

BESIDES thus noticing such features in the rocks of each country as

were necessary to the identification of the strata, geologists have

had many other phenomena of the earth's surface and materials

presented to their notice; and these they have, to a certain extent,

attempted to generalize, so as to obtain on this subject what we

have elsewhere termed the Laws of Phenomena, which are the best

materials for physical theory. Without dwelling long upon these, we

may briefly note some of the most obvious. Thus it has been observed

that mountain ranges often consist of a ridge of subjacent rock, on

which lie, on each side, strata sloping from the ridge. Such a ridge

is an _Anticlinal Line_, a _Mineralogical Axis_. The sloping strata

present their _Escarpements_, or steep edges, to this axis. Again,

in mining countries, the _Veins_ which contain the ore are usually a

system of _parallel_ and nearly vertical partitions in the rock; and

these are, in very many cases, intersected by another system of

veins parallel to each other and nearly _perpendicular_ to the

former. Rocky regions are often intersected by _Faults_, or fissures

interrupting the strata, in which the rock on one side the fissure

appears to have been at first continuous with that on the other, and

shoved aside or up or down after the fracture. Again, besides these

larger fractures, rocks have _Joints_,--separations, or tendencies

to separate in some directions rather than in others; and a _slaty

Cleavage_, in which the parallel subdivisions may be carried on, so

as to produce laminæ of indefinite thinness. As an example of those

laws of phenomena of which we have spoken, we may instance the

general law asserted by Prof. {538} Sedgwick (not, however, as free

from exception), that in one particular class of rocks the slaty

Cleavage _never_ coincides with the Direction of the strata.

The phenomena of metalliferous veins may be referred to, as another

large class of facts which demand the notice of the geologist. It

would be difficult to point out briefly any general laws which

prevail in such cases; but in order to show the curious and complex

nature of the facts, it may be sufficient to refer to the

description of the metallic veins of Cornwall by Mr. Carne;[56\18]

in which the author maintains that their various contents, and the

manner in which they cut across, and _stop_, or _shift_, each other,

leads naturally to the assumption of veins of no less than six or

eight different ages in one kind of rock.

[Note 56\18: _Transactions of the Geol. Soc. of Cornwall_, vol. ii.]

Again, as important characters belonging to the physical history of

the earth, and therefore to geology, we may notice all the general

laws which refer to its temperature;--both the laws of climate, as

determined by the _isothermal lines_, which Humboldt has drawn, by

the aid of very numerous observations made in all parts of the

world; and also those still more curious facts, of the increase of

temperature which takes place as we descend in the solid mass. The

latter circumstance, after being for a while rejected as a fable, or

explained away as an accident, is now generally acknowledged to be

the true state of things in many distant parts of the globe, and

probably in all.

Again, to turn to cases of another kind: some writers have

endeavored to state in a general manner laws according to which the

members of the geological series succeed each other; and to reduce

apparent anomalies to order of a wider kind. Among those who have

written with such views, we may notice Alexander von Humboldt,

always, and in all sciences, foremost in the race of generalization.

In his attempt to extend the doctrine of geological equivalents from

the rocks of Europe[57\18] to those of the Andes, he has marked by

appropriate terms the general modes of geological succession. "I

have insisted," he says[58\18] "principally upon the phenomena of

_alternation_, _oscillation_, and _local suppression_, and on those

presented by the _passages_ of formations from one to another, by

the effect of an _interior developement_."

[Note 57\18: _Gissement des Roches dans les deux Hemisphères_, 1823.]

[Note 58\18: Pref. p. vi.]

The phenomena of alternation to which M. de Humboldt here refers

are, in fact, very curious: as exhibiting a mode in which the

transitions from one formation to another may become gradual and

insensible, {539} instead of sudden and abrupt. Thus the coal

measures in the south of England are above the mountain limestone;

and the distinction of the formations is of the most marked kind.

But as we advance northward into the coal-field of Yorkshire and

Durham, the subjacent limestone begins to be subdivided by thick

masses of sandstone and carbonaceous strata, and passes into a

complex deposit, not distinguishable from the overlying coal

measures; and in this manner the transition from the limestone to

the coal is made by alternation. Thus, to use another expression of

M. de Humboldt's in ascending from the limestone, the coal, before

we quit the subjacent stratum, _preludes_ to its fuller exhibition

in the superior beds.

Again, as to another point: geologists have gone on up to the

present time endeavoring to discover general laws and facts, with

regard to the position of mountain and mineral masses upon the

surface of the earth. Thus M. Von Buch, in his physical description

of the Canaries, has given a masterly description of the lines of

volcanic action and volcanic products, all over the globe. And, more

recently, M. Elie de Beaumont has offered some generalizations of a

still wider kind. In this new doctrine, those mountain ranges, even

in distant parts of the world, which are of the same age, according

to the classifications already spoken of, are asserted to be

parallel[59\18] to each other, while those ranges which are of

different ages lie in different directions. This very wide and

striking proposition may be considered as being at present upon its

trial among the geologists of Europe.[60\18]

[Note 59\18: We may observe that the notion of parallelism, when

applied to lines drawn on _remote_ portions of a globular surface,

requires to be interpreted in so arbitrary a manner, that we can

hardly imagine it to express a physical law.]

[Note 60\18: Mr. Lyell, in the sixth edition of his _Principles_, B.

i. c. xii., has combated the hypothesis of M. Elie de Beaumont,

stated in the text. He has argued both against the catastrophic

character of the elevation of mountain chains, and the parallelism

of the contemporaneous ridges. It is evident that the former

doctrine may be true, though the latter be shown to be false.]

Among the organic phenomena, also, which have been the subject of

geological study, general laws of a very wide and comprehensive kind

have been suggested, and in a greater or less degree confirmed by

adequate assemblages of facts. Thus M. Adolphe Brongniart has not

only, in his _Fossil Flora_, represented and skilfully restored a

vast number of the plants of the ancient world; but he has also, in

the _Prodromus_ of the work, presented various important and

striking views of the general character of the vegetation of former

periods, as {540} insular or continental, tropical or temperate. And

M. Agassiz, by the examination of an incredible number of specimens

and collections of fossil fish, has been led to results which,

expressed in terms of his own ichthyological classification, form

remarkable general laws. Thus, according to him,[61\18] when we go

below the lias, we lose all traces of two of the four orders under

which he comprehends all known kinds of fish; namely, the

_Cycloïdean_ and the _Ctenoïdean_; while the other two orders, the

_Ganoïdean_ and _Placoïdean_, rare in our days, suddenly appear in

great numbers, together with large sauroid and carnivorous fishes.

Cuvier, in constructing his great work on ichthyology, transferred

to M. Agassiz the whole subject of fossil fishes, thus showing how

highly he esteemed his talents as a naturalist. And M. Agassiz has

shown himself worthy of his great predecessor in geological natural

history, not only by his acuteness and activity, but by the

comprehensive character of his zoological philosophy, and by the

courage with which he has addressed himself to the vast labors which

lie before him. In his _Report on the Fossil Fish discovered in

England_, published in 1835, he briefly sketches some of the large

questions which his researches have suggested; and then adds,[62\18]

"Such is the meagre outline of a history of the highest interest,

full of curious episodes, but most difficult to relate. To unfold

the details which it contains will be the business of my life."

[Note 61\18: Greenough, _Address to Geol. Soc._ 1835, p. 19.]

[Note 62\18: _Brit. Assoc. Report_, p. 72.]

[2nd Ed.] [In proceeding downwards through the series of formations

into which geologists have distributed the rocks of the earth, one

class of organic forms after another is found to disappear. In the

Tertiary Period we find all the classes of the present world:

Mammals, Birds, Reptiles, Fishes, Crustaceans, Mollusks, Zoophytes.

In the Secondary Period, from the Chalk down to the New Red

Sandstone, Mammals are not found, with the minute exception of the

marsupial _amphitherium_ and _phascolotherium_ in the Stonesfield

slate. In the Carboniferous and Devonian period we have no large

Reptiles, with, again, a minute amount of exception. In the lower

part of the Silurian rocks, Fishes vanish, and we have no animal

forms but Mollusks, Crustaceans and Zoophytes.

The Carboniferous, Devonian and Silurian formations, thus containing

the oldest forms of life, have been termed _palæozoic_. The

boundaries of the life-bearing series have not yet been determined;

but the series in which vertebrated animals do not appear has been

{541} provisionally termed _protozoic_, and the lower Silurian rocks

may probably be looked upon as its upper members. Below this,

geologists place a _hypozoic_ or _azoic_ series of rocks.

Geologists differ as to the question whether these changes in the

inhabitants of the globe were made by determinate steps or by

insensible gradations. M. Agassiz has been led to the conviction

that the organized population of the globe was renewed in the

interval of each principal member of its formations.[63\18] Mr.

Lyell, on the other hand, conceives that the change in the

collection of organized beings was gradual, and has proposed on this

subject an hypothesis which I shall hereafter consider.]

[Note 63\18: _Brit. Assoc. Report_ 1842, p. 83.]

_Sect._ 2.--_Transition to Geological Dynamics._

WHILE we have been giving this account of the objects with which

Descriptive Geology is occupied, it must have been felt how

difficult it is, in contemplating such facts, to confine ourselves

to description and classification. Conjectures and reasonings

respecting the causes of the phenomena force themselves upon us at

every step; and even influence our classification and nomenclature.

Our Descriptive Geology impels us to endeavor to construct a

Physical Geology. This close connexion of the two branches of the

subject by no means invalidates the necessity of distinguishing

them: as in Botany, although the formation of a Natural System

necessarily brings us to physiological relations, we still

distinguish Systematic from Physiological Botany.

Supposing, however, our Descriptive Geology to be completed, as far

as can be done without considering closely the causes by which the

strata have been produced, we have now to enter upon the other

province of the science, which treats of those causes, and of which

we have already spoken, as _Physical Geology_. But before we can

treat this department of speculation in a manner suitable to the

conditions of science, and to the analogy of other parts of our

knowledge, a certain intermediate and preparatory science must be

formed, of which we shall now consider the origin and progress.

{{542}}

GEOLOGICAL DYNAMICS.

CHAPTER V.

INORGANIC GEOLOGICAL DYNAMICS.

_Sect._ 1.--_Necessity and Object of a Science of Geological

Dynamics._

WHEN the structure and arrangement which men observed in the

materials of the earth instigated them to speculate concerning the

past changes and revolutions by which such results had been

produced, they at first supposed themselves sufficiently able to

judge what would be the effects of any of the obvious agents of

change, as water or volcanic fire. It did not at once occur to them

to suspect, that their common and extemporaneous judgment on such

points was far from sufficient for sound knowledge;--they did not

foresee that they must create a special science, whose object should

be to estimate the general laws and effects of assumed causes,

before they could pronounce whether such causes had actually

produced the particular facts which their survey of the earth had

disclosed to them.

Yet the analogy of the progress of knowledge on other subjects

points out very clearly the necessity of such a science. When

phenomenal astronomy had arrived at a high point of completeness, by

the labors of ages, and especially by the discovery of Kepler's

laws, astronomers were vehemently desirous of knowing the causes of

these motions; and sanguine men, such as Kepler, readily conjectured

that the motions were the effects of certain virtues and influences,

by which the heavenly bodies acted upon each other. But it did not

at first occur to him and his fellow-speculators, that they had not

ascertained what motions the influences of one body upon another

could produce: and that, therefore, they were not prepared to judge

whether such causes as they spoke of, did really regulate the

motions of the planets. Yet such was found to be the necessary

course of sound inference. Men needed a science of motion, in order

to arrive at a science of the {543} heavenly motions: they could not

advance in the study of the Mechanics of the heavens, till they had

learned the Mechanics of terrestrial bodies. And thus they were, in

such speculations, at a stand for nearly a century, from the time of

Kepler to the time of Newton, while the science of Mechanics was

formed by Galileo and his successors. Till that task was executed,

all the attempts to assign the causes of cosmical phenomena were

fanciful guesses and vague assertions; after that was done, they

became demonstrations. The science of _Dynamics_ enabled

philosophers to pass securely and completely from _Phenomenal

Astronomy_ to _Physical Astronomy_.

In like manner, in order that we may advance from Phenomenal Geology

to Physical Geology, we need a science of _Geological

Dynamics_;--that is, a science which shall investigate and determine

the laws and consequences of the known causes of changes such as

those which Geology considers:--and which shall do this, not in an

occasional, imperfect, and unconnected manner, but by systematic,

complete, and conclusive methods;--shall, in short, be a Science,

and not a promiscuous assemblage of desultory essays.

The necessity of such a study, as a distinct branch of geology, is

perhaps hardly yet formally recognized, although the researches

which belong to it have, of late years, assumed a much more

methodical and scientific character than they before possessed. Mr.

Lyell's work (_Principles of Geology_), in particular, has eminently

contributed to place Geological Dynamics in its proper prominent

position. Of the four books of his Treatise, the second and third

are upon this division of the subject; the second book treating of

aqueous and igneous causes of change, and the third, of changes in

the organic world.

There is no difficulty in separating this auxiliary geological

science from theoretical Geology itself, in which we apply our

principles to the explanation of the actual facts of the earth's

surface. The former, if perfected, would be a demonstrative science

dealing with general cases; the latter is an ætiological view having

reference to special facts; the one attempts to determine what

always must be under given conditions; the other is satisfied with

knowing what is and has been, and why it has been; the first study

has a strong resemblance to Mechanics, the other to philosophical

Archæology.

Since this portion of science is still so new, it is scarcely

possible to give any historical account of its progress, or any

complete survey of its shape and component parts. I can only attempt

a few notices, {544} which may enable us in some measure to judge to

what point this division of our subject is tending.

We may remark, in this as in former cases, that since we have here

to consider the formation and progress of a _science_, we must treat

as unimportant preludes to its history, the detached and casual

observations of the effects of causes of change which we find in

older writers. It is only when we come to systematic collections of

information, such as may afford the means of drawing general

conclusions; or to rigorous deductions from known laws of

nature;--that we can recognise the separate existence of geological

dynamics, as a path of scientific research.

The following may perhaps suffice, for the present, as a sketch of

the subjects of which this science treats:--the aqueous causes of

change, or those in which water adds to, takes from, or transfers,

the materials of the land:--the igneous causes; volcanoes, and,

closely connected with them, earthquakes, and the forces by which

they are produced;--the calculations which determine, on physical

principles, the effects of assumed mechanical causes acting upon

large portions of the crust of the earth;--the effect of the forces,

whatever they be, which produce the crystalline texture of rocks,

their fissile structure, and the separation of materials, of which

we see the results in metalliferous veins. Again, the estimation of

the results of changes of temperature in the earth, whether

operating by pressure, expansion, or in any other way;--the effects

of assumed changes in the superficial condition, extent, and

elevation, of terrestrial continents upon the climates of the

earth;--the effect of assumed cosmical changes upon the temperature

of this planet;--and researches of the same nature as these.

These researches are concerned with the causes of change in the

inorganic world; but the subject requires no less that we should

investigate the causes which may modify the forms and conditions of

organic things; and in the large sense in which we have to use the

phrase, we may include researches on such subjects also as parts of

Geological Dynamics; although, in truth, this department of

physiology has been cultivated, as it well deserves to be,

independently of its bearing upon geological theories. The great

problem which offers itself here, in reference to Geology, is, to

examine the value of any hypotheses by which it may be attempted to

explain the succession of different races of animals and plants in

different strata; and though it may be difficult, in this inquiry,

to arrive at any positive result, we {545} may at least be able to

show the improbability of some conjectures which have been

propounded.

I shall now give a very brief account of some of the attempts made

in these various departments of this province of our knowledge; and

in the present chapter, of Inorganic Changes.

_Sect._ 2.--_Aqueous Causes of Change._

THE controversies to which the various theories of geologists gave

rise, proceeding in various ways upon the effects of the existing

causes of change, led men to observe, with some attention and

perseverance, the actual operation of such causes. In this way, the

known effect of the Rhine, in filling up the Lake of Geneva at its

upper extremity, was referred to by De Luc, Kirwan, and others, in

their dispute with the Huttonians; and attempts were even made to

calculate how distant the period was, when this alluvial deposit

first began. Other modern observers have attended to similar facts

in the natural history of rivers and seas. But the subject may be

considered as having first assumed its proper form, when taken up by

Mr. Von Hoff; of whose _History of the Natural Changes of the

Earth's surface which are proved by Tradition_, the first part,

treating of aqueous changes, appeared in 1822. This work was

occasioned by a Prize Question of the Royal Society of Göttingen,

promulgated in 1818; in which these changes were proposed as the

subject of inquiry, with a special reference to geology. Although

Von Hoff does not attempt to establish any general inductions upon

the facts which his book contains, the collection of such a body of

facts gave almost a new aspect to the subject, by showing that

changes in the relative extent of land and water were going on at

every time, and almost at every place; and that mutability and

fluctuation in the form of the solid parts of the earth, which had

been supposed by most persons to be a rare exception to the common

course of events, was, in fact, the universal rule. But it was Mr.

Lyell's _Principles of Geology, being an attempt to explain the

former Changes of the Earth's Surface by the Causes now in action_

(of which the first volume was published in 1830), which disclosed

the full effect of such researches on geology; and which attempted

to present such assemblages of special facts, as examples of general

laws. Thus this work may, as we have said, be looked upon as the

beginning of Geological Dynamics, at least among us. Such

generalizations and applications as it contains give the most lively

{546} interest to a thousand observations respecting rivers and

floods, mountains and morasses, which otherwise appear without aim

or meaning; and thus this department of science cannot fail to be

constantly augmented by contributions from every side. At the same

time it is clear, that these contributions, voluminous as they must

become, must, from time to time, be resolved into laws of greater

and greater generality; and that thus alone the progress of this, as

of all other sciences, can be furthered.

I need not attempt any detailed enumeration of the modes of aqueous

action which are here to be considered. Some are destructive, as

when the rivers erode the channels in which they flow; or when the

waves, by their perpetual assault, shatter the shores, and carry the

ruins of them into the abyss of the ocean. Some operations of the

water, on the other hand, add to the land; as when _deltas_ are

formed at the mouths of rivers or when calcareous springs form

deposits of _travertin_. Even when bound in icy fetters, water is by

no mean deprived of its active power; the _glacier_ carries into the

valley masses of its native mountain, and often, becoming ice-bergs,

float with a lading of such materials far into the seas of the

temperate zone. It is indisputable that vast beds of worn down

fragments of the existing land are now forming into strata at the

bottom of the ocean; and that many other effects are constantly

produced by existing aqueous causes, which resemble some, at least,

of the facts which geology has to explain.

[2nd Ed.] [The effects of glaciers above mentioned are obvious; but

the mechanism of these bodies,--the mechanical cause of their

motions,--was an unsolved problem till within a very few years. That

they slide as rigid masses;--that they advance by the expansion of

their mass;--that they advance as a collection of rigid fragments;

were doctrines which were held by eminent physicists; though a very

slight attention to the subject shows these opinions to be

untenable. In Professor James Forbes's theory on the subject

(published in his _Travels through the Alps_, 1843,) we find a

solution of the problem, so simple, and yet so exact, as to produce

the most entire conviction. In this theory, the ice of a glacier is,

on a great scale, supposed to be a plastic or viscous mass, though

small portions of it are sensibly rigid. It advances down the slope

of the valley in which it lies as a plastic mass would do,

accommodating itself to the varying shape and size of its bed, and

showing by its crevasses its mixed character between fluid and

rigid. It shows this character still more curiously by a _ribboned_

{547} _structure_ on a small scale, which is common in the solid ice

of the glacier. The planes of these _ribbons_ are, for the most

part, at right angles to the crevasses, near the sides of the

glacier, while, near its central line, they _dip_ towards the upper

part of the glacier. This structure appears to arise from the

difference of velocities of contiguous moving filaments of the icy

mass, as the crevasses themselves arise from the tension of larger

portions. Mr. Forbes has, in successive publications, removed the

objections which have been urged against this theory. In the last of

them, a Memoir in the _Phil. Trans._, 1846, (_Illustrations of the

Viscous Theory of Glacier Motion_,) he very naturally expresses

astonishment at the opposition which has been made to the theory on

the ground of the rigidity of small pieces of ice. He has himself

shown that the ice of glaciers has a plastic flexibility, by marking

forty-five points in a transverse straight line upon the Mer de

Glace, and observing them for several days. The straight line in

that time not only became oblique to the side, but also became

visibly curved.

Both Mr. Forbes and other philosophers have made it in the highest

degree probable that glaciers have existed in many places in which

they now exist no longer, and have exercised great powers in

transporting large blocks of rock, furrowing and polishing the rocks

along which they slide, and leaving lines and masses of detritus or

_moraine_ which they had carried along with them or pushed before

them. It cannot be doubted that extinct glaciers have produced some

of the effects which the geologist has to endeavor to explain. But

this part of the machinery of nature has been worked by some

theorists into an exaggerated form, in which it cannot, as I

conceive, have any place in an account of Geological Dynamics which

aims at being permanent.

The great problem of the diffusion of drift and erratic blocks from

their parent rocks to great distances, has driven geologists to the

consideration of other hypothetical machinery by which the effects

may be accounted for: especially the great _northern drift_ and

_boulders_,--the rocks from the Scandinavian chain which cover the

north of Europe on a vast area, having a length of 2000 and breadth

of from 400 to 800 miles. The diffusion of these blocks has been

accounted for by supposing them to be imbedded in icebergs, detached

from the shore, and floated into oceanic spaces, where they have

grounded and been deposited by the melting of the ice. And this mode

of action may to some extent be safely admitted into geological

speculation. For it is a matter of fact, that our navigators in

arctic and antarctic regions have {548} repeatedly seen icebergs and

icefloes sailing along laden with such materials.

The above explanation of the phenomena of drift supposes the land on

which the travelled materials are found to have been the bottom of a

sea where they were deposited. But it does not, even granting the

conditions, account for some of the facts observed;--that the drift

and the boulders are deposited in "trainées" or streaks, which, in

direction, diverge from the parent rock;--and that the boulders are

of smaller and smaller size, as they are found more remote from that

centre. These phenomena rather suggest the notion of currents of

water as the cause of the distribution of the materials into their

present situations. And though the supposition that the whole area

occupied by drift and boulders was a sea-bottom when they were

scattered over it much reduces the amount of violence which it is

necessary to assume in order to distribute the loose masses, yet

still the work appears to be beyond the possible effect of ordinary

marine currents, or any movements which would be occasioned by a

slow and gradual rising of the centre of distribution.

It has been suggested that a _sudden_ rise of the centre of

distribution would cause a motion in the surrounding ocean sufficient

to produce such an effect: and in confirmation of this reference has

been made to Mr. Scott Russell's investigations with respect to waves,

already referred to. (Book VIII.) The wave in this case would be the

_wave of translation_, in which the motion of the water is as great at

the bottom as at the top; and it has hence been asserted that by

paroxysmal elevations of 100 or 200 feet, a current of 25 or 30 miles

an hour might be accounted for. But I think it has not been

sufficiently noted that at each point this "current" is transient: it

lasts only while the wave is passing over the point, and therefore it

would only either carry a single mass the whole way with its own

velocity, or move through a short distance a series of masses over

which it successively passed. It does not appear, therefore, that we

have here a complete account of the transport of a collection of

materials, in which each part is transferred through great

distances:--except, indeed, we were to suppose a numerous succession

of paroxysmal elevations. Such a _battery_ might, by successive

shocks, transmitting their force through the water, diffuse the

fragments of the central mass over any area, however wide.

The fact that the erratic blocks are found to rest on the lower

drift, is well explained by supposing the latter to have been spread

on the {549} sea bottom while rock-bearing ice-masses floated on the

surface till they deposited their lading.

Sir R. Murchison has pointed out another operation of ice in

producing mounds of rocky masses; namely, the effects of rivers and

lakes, in climates where, as in Russia, the waters carry rocky

fragments entangled in the winter ice, and leave them in heaps at

the highest level which the waters attain.

The extent to which the effects of glaciers, now vanished, are

apparent in many places, especially in Switzerland and in England,

and other phenomena of the like tendency, have led some of the most

eminent geologists to the conviction that, interior to the period of

our present temperature, there was a _Glacial Period_, at which the

temperature of Europe was lower than it now is.]

Although the study of the common operations of water may give the

geologist such an acquaintance with the laws of his subject as may

much aid his judgment respecting the extent to which such effects

may proceed, a long course of observation and thought must be

requisite before such operations can be analysed into their

fundamental principles, and become the subjects of calculation, or

of rigorous reasoning in any manner which is as precise and certain

as calculation. Various portions of Hydraulics have an important

bearing upon these subjects, including some researches which have

been pursued with no small labor by engineers and mathematicians; as

the effects of currents and waves, the laws of tides and of rivers,

and many similar problems. In truth, however, such subjects have not

hitherto been treated by mathematicians with much success; and

probably several generations must elapse before this portion of

geological dynamics can become an exact science.

_Sect._ 3.--_Igneous Causes of Change.--Motions of the Earth's

Surface._

THE effects of volcanoes have long been noted as important and

striking features in the physical history of our globe; and the

probability of their connexion with many geological phenomena, had

not escaped notice at an early period. But it was not till more

recent times, that the full import of these phenomena was

apprehended. The person who first looked at such operations with

that commanding general view which showed their extensive connexion

with physical geology, was Alexander von Humboldt, who explored the

volcanic phenomena {550} of the New World, from 1799 to 1804. He

remarked[64\18] the linear distribution of volcanic domes,

considering them as vents placed along the edge of vast fissures

communicating with reservoirs of igneous matter, and extending

across whole continents. He observed, also, the frequent sympathy of

volcanic and terremotive action in remote districts of the earth's

surface, thus showing how deeply seated must be the cause of these

convulsions. These views strongly excited and influenced the

speculations of geologists; and since then, phenomena of this kind

have been collected into a general view as parts of a

natural-historical science. Von Hoff, in the second volume of the

work already mentioned, was one of the first who did this; "At

least," he himself says,[65\18] (1824,) "it was not known to him

that any one before him had endeavored to combine so large a mass of

facts with the general ideas of the natural philosopher, so as to

form a whole." Other attempts were, however, soon made. In 1825, M.

von Ungern-Sternberg published his book _On the Nature and Origin of

Volcanoes_,[66\18] in which, he says, his object is, to give an

empirical representation of these phenomena. In the same year, Mr.

Poulett Scrope published a work in which he described the known

facts of volcanic action; not, however, confining himself to

description; his purpose being, as his title states, to consider

"the probable causes of their phenomena, the laws which determine

their march, the disposition of their products, and their connexion

with the present state and past history of the globe; leading to the

establishment of a new theory of the earth." And in 1826, Dr.

Daubeny, of Oxford, produced _A Description of Active_ and Extinct

_Volcanoes_, including in the latter phrase the volcanic rocks of

central France, of the Rhine, of northern and central Italy, and

many other countries. Indeed, the near connexion between the

volcanic effects now going on, and those by which the basaltic rocks

of Auvergne and many other places had been produced, was, by this

time, no longer doubted by any; and therefore the line which here

separates the study of existing causes from that of past effects may

seem to melt away. But yet it is manifest that the assumption of an

identity of scale and mechanism between volcanoes now active, and

the igneous catastrophes of which the products have {551} survived

great revolutions on the earth's surface, is hypothetical; and all

which depends on this assumption belongs to theoretical geology.

[Note 64\18: Humboldt, _Relation Historique_; and his other works.]

[Note 65\18: Vol. ii. Prop. 5.]

[Note 66\18: _Werden und Seyn des Vulkanischen Gebirges_. Carlsruhe,

1825.]

Confining ourselves, then, to volcanic effects, which have been

produced, certainly or probably, since the earth's surface assumed

its present form, we have still an ample exhibition of powerful

causes of change, in the streams of lava and other materials emitted

in eruptions; and still more in the earthquakes which, as men easily

satisfied themselves, are produced by the same causes as the

eruptions of volcanic fire.

Mr. Lyell's work was important in this as in other portions of this

subject. He extended the conceptions previously entertained of the

effects which such causes may produce, not only by showing how great

these operations are historically known to have been, and how

constantly they are going on, if we take into our survey the whole

surface of the earth; but still more, by urging the consequences

which would follow in a long course of time from the constant

repetition of operations in themselves of no extraordinary amount. A

lava-stream many miles long and wide, and several yards deep, a

subsidence or elevation of a portion of the earth's surface of a few

feet, are by no means extraordinary facts. Let these operations,

said Mr. Lyell, be repeated thousands of times; and we have results

of the same order with the changes which geology discloses.

The most mitigated earthquakes have, however, a character of

violence. But it has been thought by many philosophers that there is

evidence of a change of level of the land in cases where none of

these violent operations are going on. The most celebrated of these

cases is Sweden; the whole of the land from Gottenburg to the north

of the Gulf of Bothnia has been supposed in the act of rising,

slowly and insensibly, from the surrounding waters. The opinion of

such a change of level has long been the belief of the inhabitants;

and was maintained by Celsius in the beginning of the eighteenth

century. It has since been conceived to be confirmed by various

observations of marks cut on the face of the rock; beds of shells,

such as now live in the neighboring seas, raised to a considerable

height; and other indications. Some of these proofs appear doubtful;

but Mr. Lyell, after examining the facts upon the spot in 1834,

says, "In regard to the proposition that the land, in certain parts

of Sweden, is gradually rising, I have no hesitation in assenting to

it, after my visit to the districts above alluded to."[67\18] If

this conclusion be generally accepted by {552} geologists, we have

here a daily example of the operation of some powerful agent which

belongs to geological dynamics; and which, for the purposes of the

geological theorist, does the work of the earthquake upon a very

large scale, without assuming its terrors.

[Note 67\18: _Phil. Trans._ 1835, p. 32.]

[2nd Ed.] [Examples of changes of level of large districts occurring

at periods when the country has been agitated by earthquakes are

well ascertained, as the rising of the coast of Chili in 1822, and

the subsidence of the district of Cutch, in the delta of the Indus,

in 1819. (Lyell, B. II. c. xv.) But the cases of more slow and

tranquil movement seem also to be established. The gradual secular

rise of the shore of the Baltic, mentioned in the text, has been

confirmed by subsequent investigation. It appears that the rate of

elevation increases from Stockholm, where it is only a few inches in

a century, to the North Cape, where it is several feet. It appears

also that several other regions are in a like state of secular

change. The coast of Greenland is sinking. (Lyell, B. II. c. xviii.)

And the existence of "raised beaches" along various coasts is now

generally accepted among geologists. Such beaches, anciently forming

the margin of the sea, but now far above it, exist in many places;

for instance, along a great part of the Scotch coast; and among the

raised beaches of that country we ought probably, with Mr. Darwin,

to include the "parallel roads" of Glenroy, the subject, in former

days, of so much controversy among geologists and antiquaries.

Connected with the secular rise and fall of large portions of the

earth's surface, another agency which plays an important part in

Geological dynamics has been the subject of some bold yet singularly

persuasive speculations by Mr. Darwin. I speak of the formation of

Coral, and Coral Reefs. He says that the coral-building animal works

only at small and definite distances below the surface. How then are

we to account for the vast number of coral islands, rings, and

reefs, which are scattered over the Pacific and Indian Oceans! Can

we suppose that there are so many mountains, craters, and ridges,

all exactly within a few feet of the same height through this vast

portion of the globe's surface? This is incredible. How then are we

to explain the facts? Mr. Darwin replies, that if we suppose the

land to subside slowly beneath the sea, and at the same time suppose

the coralline zoophytes to go on building, so that their structure

constantly rises nearly to the surface of the water, we shall have

the facts explained. A submerged island will produce a ring; a long

coast, a barrier reef; and so on. Mr. Darwin also notes other

phenomena, as {553} elevated beds of coral, which, occurring in

other places, indicate a recent rising of the land; and on such

grounds as these he divides the surface of those parts of the ocean

into regions of elevation and of depression.