But in the subjects where we principally find such a

subordination of classes as we have spoken of, this process

of deduction is rarely of much prominence: for example, in

the branches of natural history. Yet it is in these subjects

that the existence and importance of these characteristic

marks, which we have spoken of, principally comes into view.

In treating of these marks, however, we enter upon methods

which are technical and scientific, not popular and common.

And before we make this transition, we have a remark to make

on the manner in which writers, without reference to physics

or natural history, have spoken of kinds, their

subordination, and their marks.

11. '_The Five Words._'--These things,--the Nature and

Relations of Classes,--were, in fact, the subjects of minute

and technical treatment by the logicians of the school of

Aristotle. Porphyry wrote an Introduction to the

_Categories_ of that philosopher, which is entitled _On the

Five Words_. The 'Five Words' are _Genus_, _Species_,

_Difference_, _Property_, _Accident_. Genus and Species are

superior and inferior classes, and are stated[2\8] to be

capable of repeated subordination. The 'most {106} general

Genus' is the widest class; the 'most special Species' the

narrowest. Between these are intermediate classes, which are

Genera with regard to those below, and Species with regard

to those above them. Thus Being is the most general Genus;

under this is Body; under Body is Living Body; under this

again Animal; under Animal is Rational Animal, or Man; under

Man are Socrates and Plato, and other individual men.

[Note 2\8: Porphyr. _Isagog._ c. 23.]

The _Difference_ is that which is added to the genus to make

the species; thus Rational is the Difference by which the

genus Animal is made the species Man; the Difference in this

Technical sense is the 'Specific,' or species-making

Difference[3\8]. It forms the Definition for the purposes of

logic, and corresponds to the 'Character' (specific or

generic) of the Natural Historians. Indeed several of them,

as, for instance, Linnæus, in his _Philosophia Botanica_,

always call these Characters the _Difference_, by a

traditional application of the Peripatetic terms of art.

[Note 3\8: εἰδοποιός.]

Of the other two words, the Property is that which though

not employed in defining the class, belongs to every part of

it[4\8]: it is, 'What happens to all the class, to it alone,

and at all times; as _to be capable of laughing_ is a

Property of man.'

[Note 4\8: _Isagog._ c. 4]

The Accident is that which may be present and absent without

the destruction of the subject, as to sleep is an Accident

(a thing which happens) to man.

I need not dwell further on this system of technicalities.

The most remarkable points in it are those which I have

already noticed; the doctrine of the successive

Subordination of genera, and the fixing attention upon the

Specific Difference. These doctrines, though invented in

order to make reasoning more systematic, and at a period

anterior to the existence of any Classificatory Science,

have, by a curious contrast with the intentions of their

founders, been of scarcely {107} any use in sciences of

_Reasoning_, but have been amply applied and developed in

the _Natural History_ which arose in later times.

We must now treat of the principles on which this science

(Natural History) proceeds, and explain what peculiar and

technical processes it employs in addition to those of

common thought and common language.

{{108}}

CHAPTER II.

THE METHODS OF NATURAL HISTORY, AS REGULATED BY THE IDEA OF

LIKENESS.

SECT. I.--_Natural History in general._

1. _Idea of Likeness in Natural History._--THE various

branches of Natural History, in so far as they are

classificatory sciences merely, and do not depend upon

physiological views, rest upon the same Idea of Likeness

which is the ground of the application of the names, more or

less general, of common language. But the nature of science

requires that, for her purposes, this Idea should be applied

in a more exact and rigourous manner than in its common and

popular employment; just as occurs with regard to the other

Ideas on which science is founded;--for instance, as the

idea of space gives rise, in popular use, to the relations

implied in the prepositions and adjectives which refer to

position and form, and in its scientific development gives

rise to the more precise relations of geometry.

The way in which the Idea of Likeness has been applied, so

as to lead to the construction of a science, is best seen in

Botany: for, in the Classification of Animals, we are

inevitably guided by a consideration of the _function_ of

parts; that is, by an idea of _purpose_, and not of likeness

merely: and in Mineralogy, the attempts at classification on

the principles of Natural History have been hitherto very

imperfectly successful. But in Botany we have an example of

a branch of knowledge in which systematic classification has

been effected with great beauty and advantage; and in which

the peculiarities and principles on which such {109}

classification must depend have been carefully studied. Many

of the principal botanists, as Linnæus, Adanson, Decandolle,

have not only practically applied, but have theoretically

enunciated, what they held to be the sound maxims of

classificatory science: and have thus enabled us to place

before the reader with confidence the philosophy of this

kind of science.

2. _Condition of its Use._--We may begin by remarking that

the Idea of Likeness, in its systematic employment, is

governed by the same principle which we have already spoken

of as regulating the distribution of things into kinds, and

the assignment of names in unsystematic thought and speech;

namely, the condition that _general propositions shall be

possible_. But as in this case the propositions are to be of

a scientific form and exactness, the likeness must be

treated with a corresponding precision; and its consequences

traced by steady and distinct processes. Naturalists must,

for their purposes, employ the resemblances of objects in a

technical manner. This technical process may be considered

as consisting of three steps;--The fixation of the

resemblances; The use of them in making a classification;

The means of applying the classification. These three steps

may be spoken of as the _Terminology_, the _Plan of the

System_, and the _Scheme of the Characters_.

SECT. II.--_Terminology._[5\8]

[Note 5\8: Decandolle and others use the term _Glossology_

instead of Terminology, to avoid the blemish of a word

compounded of two parts taken from different languages. The

convenience of treating the termination _ology_ (and a few

other parts of compounds) as not restricted to Greek

combinations, is so great, that I shall venture, in these

cases, to disregard this philological scruple.]

3. _Terminology_ signifies the collection of _terms_, or

technical words, which belong to the science. But in fixing

the meaning of the terms, at least of the descriptive terms,

we necessarily fix, at the same time, the perceptions and

notions which the terms are to {110} convey; and thus the

Terminology of a classificatory science exhibits the

elements of its substance as well as of its language. A

large but indispensable part of the study of botany (and of

mineralogy and zoology also,) consists in the acquisition of

the peculiar vocabulary of the science.

The meaning of technical terms can be fixed in the first

instance only by convention, and can be made intelligible

only by presenting to the senses that which the terms are to

signify. The knowledge of a colour by its name can only be

taught through the eye. No description can convey to a

hearer what we mean by _apple-green_ or _French grey_. It

might, perhaps, be supposed that, in the first example, the

term _apple_, referring to so familiar an object,

sufficiently suggests the colour intended. But it may easily

be seen that this is not true; for apples are of many

different hues of green, and it is only by a conventional

selection that we can appropriate the term to one special

shade. When this appropriation is once made, the term refers

to the sensation, and not to the parts of this term; for

these enter into the compound merely as a help to the

memory, whether the suggestion be a natural connexion as in

'apple-green,' or a casual one as in 'French grey.' In order

to derive due advantage from technical terms of this kind,

they must be associated _immediately_ with the perception to

which they belong; and not connected with it through the

vague usages of common language. The memory must retain the

sensation; and the technical word must be understood as

directly as the most familiar word, and more distinctly.

When we find such terms as _tin-white_ or _pinchbeck-brown_,

the metallic colour so denoted ought to start up in our

memory without delay or search.

This, which it is most important to recollect with respect

to the simpler properties of bodies, as colour and form, is

no less true with respect to more compound notions. In all

cases the term is fixed to a peculiar meaning by convention;

and the student, in order to use the word, must be

completely familiar with the convention, so that he has no

need to frame {111} conjectures from the word itself. Such

conjectures would always be insecure, and often erroneous.

Thus the term _papilionaceous_, applied to a flower, is

employed to indicate, not only a resemblance to a butterfly,

but a resemblance arising from five petals of a certain

peculiar shape and arrangement; and even if the resemblance

to a butterfly were much stronger than it is in such cases,

yet if it were produced in a different way, as, for example,

by one petal, or two only, instead of a 'standard,' two

'wings,' and a 'keel' consisting of two parts more or less

united into one, we should no longer be justified in

speaking of it as a 'papilionaceous' flower.

The formation of an exact and extensive descriptive language

for botany has been executed with a degree of skill and

felicity, which, before it was attained, could hardly have

been dreamt of as attainable. Every part of a plant has been

named; and the form of every part, even the most minute, has

had a large assemblage of descriptive terms appropriated to

it, by means of which the botanist can convey and receive

knowledge of form and structure, as exactly as if each

minute part were presented to him vastly magnified. This

acquisition was part of the Linnæan Reform, of which we have

spoken in the _History_. 'Tournefort,' says Decandolle[6\8],

'appears to have been the first who really perceived the

utility of fixing the sense of terms in such a way as always

to employ the same word in the same sense, and always to

express the same idea by the same word; but it was Linnæus

who really created and fixed this botanical language, and

this is his fairest claim to glory, for by this fixation of

language he has shed clearness and precision over all parts

of the science.'

[Note 6\8: _Theor. Elem._ p. 327.]

It is not necessary here to give any detailed account of the

terms of botany. The fundamental ones have been gradually

introduced, as the parts of plants were more carefully and

minutely examined. Thus the flower was successively

distinguished into the _calyx_, {112} the _corolla_, the

_stamens_, and the _pistils_: the sections of the corolla

were termed _petals_ by Columna; those of the calyx were

called _sepals_ by Necker[7\8]. Sometimes terms of greater

generality were devised; as _perianth_ to include the calyx

and corolla, whether one or both of these were present[8\8];

_pericarp_ for the part inclosing the grain, of whatever

kind it be, fruit, nut, pod, &c. And it may easily be

imagined that descriptive terms may, by definition and

combination, become very numerous and distinct. Thus leaves

may be called _pinnatifid_[9\8], _pinnatipartite_,

_pinnatisect_, _pinnatilobate_, _palmatifid_,

_palmatipartite_, &c., and each of these words designates

different combinations of the modes and extent of the

divisions of the leaf with the divisions of its outline. In

some cases arbitrary numerical relations are introduced into

the definition: thus a leaf is called _bilobate_[10\8] when

it is divided into two parts by a notch; but if the notch go

to the middle of its length, it is _bifid_; if it go near

the base of the leaf, it is _bipartite_; if to the base, it

is _bisect_. Thus, too, a pod of a cruciferous plant is a

_silica_[11\8] if it be four times as long as it is broad,

but if it be shorter than this it is a _silicula_. Such

terms being established, the form of the very complex leaf

or frond of a fern is exactly conveyed by the following

phrase: 'fronds rigid pinnate, pinnæ recurved subunilateral

pinnatifid, the segments linear undivided or bifid

spinuloso-serrate[12\8].'

[Note 7\8: Decandolle, 329]

[Note 8\8: For this Erhart and Decandolle use _Perigone_.]

[Note 9\8: Dec. 318.]

[Note 10\8: _Ib._ 493.]

[Note 11\8: _Ib._ 422.]

[Note 12\8: Hooker, _Brit. Flo._ p. 457. _Hymenophyllum

Wilsoni_, Scottish filmy-fern, abundant in the highlands of

Scotland and about Killarney.]

Other characters, as well as form, are conveyed with the

like precision: Colour by means of a classified scale of

colours, as we have seen in speaking of the Measures of

Secondary Qualities; to which, however, we must add, that

the naturalist employs arbitrary names, (such as we have

already quoted,) and not mere numerical exponents, to

indicate a certain number of {113} selected colours. This

was done with most precision by Werner, and his scale of

colours is still the most usual standard of naturalists.

Werner also introduced a more exact terminology with regard

to other characters which are important in mineralogy, as

lustre, hardness. But Mohs improved upon this step by giving

a numerical scale of hardness, in which _talc_ is 1,

_gypsum_ 2, _calc spar_ 3, and so on, as we have already

explained in the History of Mineralogy. Some properties, as

specific gravity, by their definition give at once a

numerical measure; and others, as crystalline form, require

a very considerable array of mathematical calculation and

reasoning, to point out their relations and gradations. In

all cases the features of likeness in the objects must be

rightly apprehended, in order to their being expressed by a

distinct terminology. Thus no terms could describe crystals

for any purpose of natural history, till it was discovered

that in a class of minerals the proportion of the faces

might vary, while the angle remained the same. Nor could

crystals be described so as to distinguish species, till it

was found that the derived and primitive forms are connected

by very simple relations of space and number. The discovery

of the mode in which characters must be apprehended so that

they may be considered as _fixed_ for a class, is an

important step in the progress of each branch of Natural

History; and hence we have had, in the History of Mineralogy

and Botany, to distinguish as important and eminent persons

those who made such discoveries, Romé de Lisle and Haüy,

Cesalpinus and Gesner.

By the continued progress of that knowledge of minerals,

plants, and other natural objects, in which such persons

made the most distinct and marked steps, but which has been

constantly advancing in a more gradual and imperceptible

manner, the most important and essential features of

similarity and dissimilarity in such objects have been

selected, arranged, and fitted with names; and we have thus

in such departments, systems of Terminology which fix our

attention upon the resemblances which it is proper to

consider, and {114} enable us to convey them in words. We

have now to speak of the mode in which such resemblances

have been employed in the construction of a Systematic

Classification.

SECT. III. _The Plan of the System._

4. The collection of sound views and maxims by which the

resemblances of natural objects are applied so as to form a

scientific classification, is a department of the philosophy

of natural history which has been termed by some writers (as

Decandolle), _Taxonomy_, as containing the _Laws_ of the

_Taxis_ (_arrangement_). By some Germans this has been

denominated _Systematik_; if we could now form a new

substantive after the analogy of the words _Logick_,

_Rhetorick_, and the like, we might call it _Systematick_.

But though our English writers commonly use the expression

_Systematical Botany_ for the Botany of Classification, they

appear to prefer the term _Diataxis_ for the method of

constructing the classification. The rules of such a branch

of science are curious and instructive.

In framing a Classification of objects we must attend to

their resemblances and differences. But here the question

occurs, to _what_ resemblances and differences? for a

different selection of the points of resemblance would give

different results: a plant frequently agrees in leaves with

one group of plants, in flowers with another. Which set of

characters are we to take as our guide?

The view already given of the regulative principle of all

classification, namely, that it must enable us to assert

true and general propositions, will obviously occur as

applicable here. The object of a scientific Classification

is to enable us to enunciate scientific truths: we must

therefore classify according to those resemblances of

objects (plants or any others) which bring to light such

truths.

But this reply to the inquiry, 'On what characters of

resemblance we are to found our system,' is still too

general and vague to be satisfactory. It carries us, {115}

however, as far as this;--that since the truths we are to

attend to are scientific truths, governed by precise and

homogeneous relations, we must not found our scientific

Classification on casual, indefinite, and unconnected

considerations. We must not, for instance, be satisfied with

dividing plants, as Dioscorides does, into _aromatic_,

_esculent_, _medicinal_ and _vinous_; or even with the long

prevalent distribution into _trees_, _shrubs_, and _herbs_;

since in these subdivisions there is no consistent

principle.

5. _Latent Reference to Natural Affinity._--But there may be

several kinds of truths, all exact and coherent, which may

be discovered concerning plants or any other natural

objects; and if this should be the case, our rule leaves us

still at a loss in what manner our classification is to be

constructed. And, historically speaking, a much more serious

inconvenience has been this;--that the task of

classification of plants was necessarily performed when the

general laws of their form and nature were very little

known; or rather, when the existence of such laws was only

just beginning to be discerned. Even up to the present day,

the general propositions which botanists are able to assert

concerning the structure and properties of plants, are

extremely imperfect and obscure.

We are thus led to this conclusion:--that the Idea of

Likeness could not be applied so as to give rise to a

scientific Classification of plants, till considerable

progress was made in studying the general relations of

vegetable form and life; and that the selection of the

resemblances which should be taken into account, must depend

upon the nature of the relations which were then brought

into view.

But this amounts to saying that, in the consideration of the

Classification of vegetables, other Ideas must be called

into action as well as the Idea of Likeness. The additional

general views to which the more intimate study of plants

leads, must depend, like all general truths, upon some

regulating Idea which gives unity to scattered facts. No

progress could be made in botanical knowledge without the

{116} operation of such principles: and such additional

Ideas must be employed, besides those of mere likeness and

unlikeness, in order to point out that Classification which

has a real scientific value.

Accordingly, in the classificatory sciences, Ideas other

than Likeness do make their appearance. Such Ideas in botany

have influenced the progress of the science, even before

they have been clearly brought into view. We have especially

the Idea of Affinity, which is the basis of all Natural

Systems of Classification, and which we shall consider in a

succeeding chapter. The assumption that there _is_ a Natural

System, an assumption made by all philosophical botanists,

implies a belief in the existence of Natural Affinity, and

is carried into effect by means of principles which are

involved in that Idea. But as the formation of all systems

of classification must involve, in a great degree, the Idea

of Resemblance and Difference, I shall first consider the

effect of that Idea, before I treat specially of Natural

Affinity.

6. _Natural Classes._--Many attempts were made to classify

vegetables before the rules which govern a natural system

were clearly apprehended. Botanists agree in esteeming some

characters as of more value than others, before they had

agreed upon any general rules or principles for estimating

the relative importance of the characters. They were

convinced of the necessity of adding other considerations to

that of Resemblance, without seeing clearly what these

others ought to be. They aimed at a Natural Classification,

without knowing distinctly in what manner it was to be

Natural.

The attempts to form _Natural Classes_, therefore, in the

first part of their history, belong to the Idea of Likeness,

though obscurely modified, even from an early period, by the

Ideas of Affinity, and even of Function and of Development.

Hence Natural Classes may, to a certain extent, be treated

of in this place.

Natural Classes are opposed to Artificial Classes which are

understood to be regulated by an _assumed_ {117} character.

Yet no classes can be so absolutely Artificial in this

sense, as to be framed upon characters _arbitrarily_

assumed; for instance, no one would speak of a class of

shrubs defined by the circumstance of each having a hundred

leaves: for of such a class no assertion could be made, and

therefore the class could never come under our notice. In

what sense then are Artificial Classes to be understood, as

opposed to Natural?

7. _Artificial Classes._--To this question, the following is

the answer. When Natural Classes of a certain small extent

have been formed, a system may be devised which shall be

regulated by a few selected characters, and which shall not

dissever these small Natural Classes, but conform to them as

far as they go. If these selected characters be then made

absolute and imperative, and if we abandon all attempt to

obtain Natural Classes of any higher order and wider extent,

we form an Artificial System.

Thus in the Linnæan System of Botanical Classification, it

is assumed that certain natural groups, namely, Species and

Genera, are established; it is conceived, moreover, that the

division of Classes according to the number of stamens and

of pistils does not violate the natural connexions of

Species and Genera. This arrangement, according to the

number of stamens and pistils, (further modified in certain

cases by other considerations,) is then made the ground of

all the higher divisions of plants, and thus we have an

Artificial System.

It has been objected to this view, that the Linnæan

Artificial System does not in all cases respect the

boundaries of genera, but would, if rigorously applied,

distribute the species of the same genus into different

artificial classes; it would divide, for instance, the

genera _Valeriana_, _Geranium_[13\8], &c. To this we must

reply, that so far as the Linnæan System does this, it is an

imperfect Artificial System. Its great merit is in its

making such a disjunction in comparatively so {118} few

cases; and in the artificial characters being, for the most

part, obvious and easily applied.

[Note 13\8: Decand. _Theor. Elem._ p. 45.]

8. _Are Genera Natural_?--It has been objected also that

Genera are not Natural groups. Linnæus asserts in the most

positive manner that they are[14\8]. On which Adanson

observes[15\8], 'I know not how any Botanist can maintain

such a thesis: that which is certain is, that up to the

present time no one has been able to prove it, nor to give

an exact definition of a natural genus, but only of an

artificial.' He then brings several arguments to confirm

this view.

[Note 14\8: _Phil. Bot._ Art. 165.]

[Note 15\8: _Famille de Ph._ Pref. cv.]

But we are to observe, in answer to this, that Adanson

improperly confounds the recognition of the existence of a

natural group with the invention of a technical mark or

definition of it. Genera are groups of species associated in

virtue of natural affinity, of general resemblance, of real

propinquity: of such groups, certain selected characters,

one or few, may usually be discovered, by which the species

may be referred to their groups. These Artificial characters

do not constitute, but indicate the genus: they are the

_Diagnosis_, not the basis of the _Diataxis_: and they are

always subject to be rejected, and to have others

substituted for them, when they violate the natural

connexion of species which a minute and enlarged study

discovers.

It is, therefore, no proof that Genera are not Natural, to

say that their artificial characters are different in

different systems. Such characters are only different

attempts to confine the variety of nature within the limits

of definition. Nor is it sufficient to say that these groups

themselves are different in different writers; that some

botanists make genera what others make only species; as

_Pedicularis_, _Rhinanthus_, _Euphrasia_,

_Antirrhinum_[16\8]. This discrepancy shows only that the

natural arrangement is not yet completely known, even in the

smaller groups; a conclusion to which we need not refuse our

assent. But in {119} opposition to these negatives, the

manner in which Genera have been established proves that

they are regulated by the principle of being natural, and by

that alone. For they are not formed according to any _à

priori_ rule. The Botanist does not take any selected or

arbitrary part or parts of the plants, and marshal his

genera according to the differences of this part. On the

contrary, the divisions of genera are sometimes made by

means of the flower; sometimes by means of the fruit: the

anthers, the stamens, the seeds, the pericarp, and the most

varied features of these parts, are used in the most

miscellaneous and unsystematic manner. Linnæus has indeed

laid down a maxim that the characteristic differences of

genera must reside in the fructification[17\8]: but Adanson

has justly remarked[18\8], that an arbitrary restriction

like this makes the groups artificial: and that in some

families other characters are more essential than those of

the fructification; as the leaves in the families of

_Aparineæ_ and _Leguminosæ_, and the disposition of the

flowers in _Labiatæ_. And Naturalists are so far from

thinking it sufficient to distribute species into genera by

_arbitrary_ marks, that we find them in many cases lamenting

the absence of good _natural_ marks: as in the families of

_Umbelliferæ_, where Linnæus declared that any one who could

find good characters of genera would deserve great

admiration, and where it is only of late that good

characters have been discovered and the arrangement

settled[19\8] by means principally of the ribs of the

fruit[20\8].

[Note 16\8: Adanson, p. cvi.]

[Note 17\8: _Phil. Bot._ Art. 162.]

[Note 18\8: Adanson, Pref. p. cxx.]

[Note 19\8: Lindley, _Nat. Syst._ p. 5.]

[Note 20\8: In like manner we find Cuvier saying of Rondelet

that he has 'un _sentiment_ très vrai des genres.' _Hist.

Ichth._ p. 39.]

It is thus clear that Genera are not established on any

assumed or preconceived basis. What, then, is the principle

which regulates botanists when they try to fix genera? What

is the arrangement which they thus wish for, without being

able to hit upon it? What is the tendency which thus drives

them from the corolla to the anthers, from the flower to the

fruit, {120} from the fructification to the leaves? It is

plain that they seek something, not of their own devising

and creating;--not anything merely conventional and

systematic; but something which they conceive to exist in

the relations of the plants themselves;--something which is

without the mind, not within;--in nature, not in art;--in

short, a Natural Order.

Thus the regulative principle of a Genus, or of any other

natural group is, that it is, or is supposed to be, natural.

And by reference to this principle as our guide, we shall be

able to understand the meaning of that indefiniteness and

indecision which we frequently find in the descriptions of

such groups, and which must appear so strange and

inconsistent to any one who does not suppose these

descriptions to assume any deeper ground of connexion than

an arbitrary choice of the botanist. Thus in the family of

the Rose-tree, we are told that the _ovules_ are _very

rarely_ erect[21\8], the _stigmata_ are _usually_ simple. Of

what use, it might be asked, can such loose accounts be? To

which the answer is, that they are not inserted in order to

distinguish the species, but in order to describe the

family, and the total relations of the ovules and of the

stigmata of the family are better known by this general

statement. A similar observation may be made with regard to

the Anomalies of each group, which occur so commonly, that

Mr. Lindley, in his _Introduction to the Natural System of

Botany_, makes the 'Anomalies' an article in each Family.

Thus, part of the character of the Rosaceæ is that they have

alternate _stipulate_ leaves, and that the _albumen_ is

_obliterated_: but yet in _Lowea_, one of the genera of this

family, the stipulæ are _absent_; and the albumen is

_present_ in another, _Neillia_. This implies, as we have

already seen, that the artificial character (or _diagnosis_

as Mr. Lindley calls it) is imperfect. It is, though very

nearly, yet not exactly, commensurate with the natural

group: and hence, in certain cases, this character is made

to yield to the general weight of natural affinities.

[Note 21\8: Lindley, _Nat. Syst._ p. 81.]

{121} 9. _Difference of Natural History and

Mathematics._--These views,--of classes determined by

characters which cannot be expressed in words,--of

propositions which state, not what happens in all cases, but

only usually,--of particulars which are included in a class

though they transgress the definition of it, may very

probably surprise the reader. They are so contrary to many

of the received opinions respecting the use of definitions

and the nature of scientific propositions, that they will

probably appear to many persons highly illogical and

unphilosophical. But a disposition to such a judgment arises

in a great measure from this;--that the mathematical and

mathematico-physical sciences have, in a great degree,

determined men's views of the general nature and form of

scientific truth; while Natural History has not yet had time

or opportunity to exert its due influence upon the current

habits of philosophizing. The apparent indefiniteness and

inconsistency of the classifications and definitions of

Natural History belongs, in a far higher degree, to all

other except mathematical speculations: and the modes in

which approximations to exact distinctions and general

truths have been made in Natural History, may be worthy our

attention, even for the light they throw upon the best modes

of pursuing truth of all kinds.

10. _Natural Groups given by Type not by Definition._--The

further development of this suggestion must be considered

hereafter. But we may here observe, that though in a Natural

Group of objects a definition can no longer be of any use as

a regulative principle, classes are not, therefore, left

quite loose, without any certain standard or guide. The

class is steadily fixed, though not precisely limited; it is

given, though not circumscribed; it is determined, not by a

boundary line without, but by a central point within; not by

what it strictly excludes, but by what it eminently

includes; by an example, not by a precept; in short, instead

of Definition we have a _Type_ for our director.

A Type is an example of any class, for instance, a species

of a genus, which is considered as eminently {122}

possessing the characters of the class. All the species

which have a greater affinity with this Type-species than

with any others, form the genus, and are ranged about it,

deviating from it in various directions and different

degrees. Thus a genus may consist of several species, which

approach very near the type, and of which the claim to a

place with it is obvious; while there may be other species

which straggle further from this central knot, and which yet

are clearly more connected with it than with any other. And

even if there should be some species of which the place is

dubious, and which appear to be equally bound by two generic

types, it is easily seen that this would not destroy the

reality of the generic groups, any more than the scattered

trees of the intervening plain prevent our speaking

intelligibly of the distinct forests of two separate hills.

The Type-species of every genus, the Type-genus of every

family, is, then, one which possesses all the characters and

properties of the genus in a marked and prominent manner.

The Type of the Rose family has alternate stipulate leaves,

wants the albumen, has the ovules not erect, has the

stigmata simple, and besides these features, which

distinguish it from the exceptions or varieties of its

class, it has the features which make it prominent in its

class. It is one of those which possess clearly several

leading attributes; and thus, though we cannot say of any

one genus that it _must_ be the Type of the family, or of

any one species that it _must_ be the Type of the genus, we

are still not wholly to seek: the Type must be connected by

many affinities with most of the others of its group; it

must be near the center of the crowd, and not one of the

stragglers.

11. It has already been repeatedly stated, as the great rule

of all classification, that the classification must serve to

assert general propositions. It may be asked _what_

propositions we are able to enunciate by means of such

classifications as we are now treating of. And the answer

is, that the collected knowledge of the characters, habits,

properties, organization, and {123} functions of these

groups and families, as it is found in the best botanical

works, and as it exists in the minds of the best botanists,

exhibits to us the propositions which constitute the

science, and to the expression of which the classification

is to serve. All that is not strictly definition, that is,

all that is not artificial character, in the descriptions of

such classes, is a statement of truths, more or less

general, more or less precise, but making up, together, the

positive knowledge which constitutes the science. As we have

said, the consideration of the properties of plants in order

to form a system of classification, has been termed

Taxonomy, or the Systematick of Botany; all the parts of the

descriptions, which, taking the system for granted, convey

additional information, are termed the _Physiography_ of the

science; and the same terms may be applied in the other

branches of Natural History.

12. _Artificial and Natural Systems._--If I have succeeded

in making it apparent that an artificial system of

characters necessarily implies natural classes which are not

severed by the artificial marks, we shall now be able to

compare the nature and objects of the Artificial and Natural

Systems; points on which much has been written in recent times.

The Artificial System is one which is, or professes to be,

entirely founded upon marks selected according to the

condition which has been stated, of not violating certain

narrow natural groups; namely in the Linnæan system, the

natural genera of plants. The marks which form the basis of

the system, being thus selected, are applied rigorously and

universally without any further regard to any other

characters or indications of affinity. Thus in the Linnæan

system, which depends mainly on the number of male organs or

stamens, and on the number of female organs or styles, the

largest divisions, or the Classes, are arranged according to

the number of the stamens, and are _monandria_, _diandria_,

_triandria_, _tetrandria_, _pentandria_, _hexandria_, and so

on: the names being formed of the Greek numerical words, and

of the word which implies _male_. And the Orders of each of

these Classes are {124} distinguished by the number of

styles, and are called _monogynia_, _digynia_, _trigynia_,

and so on, the termination of these words meaning _female_.

And so far as this numerical division and subdivision go on,

the system is a rigorous system, and strictly artificial.

But the condition that the artificial system shall leave

certain natural affinities untouched, makes it impossible to

go through the vegetable kingdom by a method of mere

numeration of stamens and styles. The distinction of flowers

with twenty and with thirty stamens is not a fixed

distinction: flowers of one and the same kind, as roses,

have, some fewer than the former, some more than the latter

number. The Artificial System, therefore, must be modified.

And there are various relations of connexion and proportion

among the stamina which are more permanent and important

than their mere number. Thus flowers with two longer and two

shorter stamens are not placed in the class _tetrandria_,

but are made a separate class _didynamia_; those with four

longer and two shorter are in like manner _tetradynamia_,

not _hexandria_; those in **which the filaments are bound

into two bundles are _diadelphia_. All these and other

classes are deviations from the plan of the earlier Classes,

and are so far defects of the artificial system; but they

are deviations requisite in order that the system may leave

a basis of natural groups, without which it would not be a

System of _Vegetables_. And as the division is still founded

on some properties of the stamens, it combines not ill with

that part of the system which depends on the number of them.

The Classes framed in virtue of these various considerations

make up an Artificial System which is tolerably coherent.

'But since the Artificial System thus regards natural

groups, in what does it differ from a Natural System?' It

differs in this:--That though it allows certain subordinate

natural groups, it merely allows _these_, and does not

endeavour to ascend to any wider natural groups. It takes

all the _higher_ divisions of its scheme from its artificial

characters, its stamens and pistils, without looking to any

natural affinities. It {125} accepts natural _Genera_, but

it does not seek natural _Families_, or Orders, or Classes.

It _assumes_ natural groups, but does not _investigate_ any;

it forms wider and higher groups, but professes to frame

them arbitrarily.

But then, on the other hand, the question occurs, 'This

being the case, what can be the use of the Artificial

System?' If its characters, in the higher stages of

classification, be arbitrary, how can it lead us to the

natural relations of plants? And the answer is, that it does

so in virtue of the original condition, that there shall be

certain natural relations which the artificial system shall

not transgress; and that its use arises from the facility

with which we can follow the artificial arrangement as far

as it goes. We can count the stamens and pistils, and thus

we know the Class and Order of our plant; and we have then

to discover its Genus and Species by means less symmetrical

but more natural. The Artificial System, though arbitrary in

a certain degree, brings us to a Class in which the whole of

each Genus is contained, and there we can find the proper

Genus by a suitable method of seeking. No Artificial System

can conduct us into the extreme of detail, but it can place

us in a situation where the detail is within our reach. We

cannot find the house of a foreign friend by its latitude

and longitude; but we may be enabled, by a knowledge of the

latitude and longitude, to find the city in which he dwells,

or at least the island; and we then can reach his abode by

following the road or exploring the locality. The Artificial

System is such a method of travelling by latitude and

longitude; the Natural System is that which is guided by a

knowledge of the country.

The Natural System, then, is that which endeavours to

arrange by the natural affinities of objects; and more

especially, which attempts to ascend from the lower natural

groups to the higher; as for example from genera to natural

families, orders, and classes. But as we have already

hinted, these expressions of natural affinities, natural

groups, and the like, when {126} considered in reference to

the idea of resemblance alone, without studying analogy or

function, are very vague and obscure. We must notice some of

the attempts which were made under the operation of this

imperfect view of the subject.

SECT. IV.--_Modes of framing Natural Systems._

13. Decandolle[22\8] distinguishes the attempts at Natural

Classifications into three sorts: those of _blind trial_

(_tâtonnement_), those of _general comparison_, and those of

_subordination of characters_. The two former do not depend

distinctly upon any principle, except resemblance; the third

refers us to other views, and must be considered in a future

chapter.

[Note 22\8: _Theor. Elem._ art 41.]

_Method of Blind Trial._--The notion of the existence of

natural classes dependent on the general resemblance of

plants,--of an affinity showing itself in different parts

and various ways,--though necessarily somewhat vague and

obscure, was acted upon at an early period, as we have seen

in the formation of genera; and was enunciated in general

terms soon after. Thus Magnolius[23\8] says that he discerns

in plants an affinity, by means of which they may be

arranged in families: 'Yet it is impossible to obtain from

the fructification alone the Characters of these families;

and I have therefore chosen those parts of plants in which

the principal characteristic marks are found, as the root,

the stem, the flower, the seed. In some plants there is even

a certain resemblance; an affinity which does not consist in

the parts considered separately, but in their totality; an

affinity which may be felt but not expressed; as we see in

the families of agrimonies and cinquefoils, which every

botanist will judge to be related, though they differ by

their roots, their leaves, their flowers, and their seeds.'

[Note 23\8: Dec. _Theor. Elem._ art. 42. Petri Magnoli,

_Prodromus Hist. Gen. Plant._ 1689.]

{127} This obscure feeling of a resemblance on the whole, an

affinity of an indefinite kind, appears fifty years later in

Linnæus's attempts. 'In the Natural Classification,' he

says[24\8], 'no _à priori_ rule can be admitted, no part of

the fructification can be taken exclusively into

consideration; but only the simple symmetry of all its

parts.' Hence though he proposed Natural Families, and even

stated the formation of such Families to be the first and

last object of all Methods, he never gave the Characters of

those groups, or connected them by any method. He even

declared it to be impossible to lay down such a system of

characters. This persuasion was the result of his having

refused to admit into his mind any Idea more profound than

that notion of Resemblance of which he had made so much and

such successful use; he would not attempt to unravel the

Ideas of Symmetry and of Function on which the clear

establishment of natural relations must depend. He even

despised the study of the inner organization of plants; and

reckoned[25\8] the _Anatomici_, who studied the anatomy and

physiology of plants and the laws of vegetation, among the

_Botanophili_, the mere amateurs of his science.

[Note 24\8: Dec. _Theor. Elem._ art 42.]

[Note 25\8: _Phil. Bot._ s. 44.]

The same notion of general resemblance and affinity,

accompanied with the same vagueness, is to be found in the

writer who least participated in the general admiration of

Linnæus, Buffon. Though it was in a great measure his love

of higher views which made him dislike what he considered

the pedantry of the Swedish school, he does not seem to have

obtained a clearer sight of the principle of the natural

method than his rival, except that he did not restrict his

Characters to the fructification. Things must be arranged by

their resemblances and differences, (he says in 1750[26\8],)

'but the resemblances and differences must be taken not from

one part but from the whole; and we must attend to the form,

the size, the habit, the number and position of the parts,

even the substance {128} of the part; and we must make use

of these elements in greater or smaller number, as we have need.'

[Note 26\8: Adanson, p. clvi. Buffon, _Hist. Nat._ t. i. p. 21.]

14. _Method of General Comparison._--A countryman of Buffon,

who shared with him his depreciating estimate of the Linnæan

system, and his wish to found a natural system upon a

broader basis, was Adanson; and he invented an ingenious

method of apparently avoiding the vagueness of the practice

of following the general feeling of resemblance. This method

consisted in making many Artificial Systems, in each of

which plants were arranged by some one part; and then

collecting those plants which came near each other in the

greatest number of those Artificial Systems, as plants

naturally the most related. Adanson gives an account[27\8]

of the manner in which this system arose in his mind. He had

gone to Senegal, animated by an intense zeal for natural

history; and there, amid the luxuriant vegetation of the

torrid zone, he found that the methods of Linnæus and

Tournefort failed him altogether as means of arranging his

new botanical treasures. He was driven to seek a new system.

'For this purpose,' he says, 'I examined plants in all their

parts, without omitting any, from the roots to the embryo,

the folding of the leaves in the bud, their mode of

sheathing[28\8], the situation and folding of the embryo and

of its radicle in the seed, relatively to the fruit; in

short, a number of particulars which few botanists notice. I

made in the first place a complete description of each

plant, putting each of its parts in separate articles, in

all its details; when new species occurred I put down the

points in which they differed, omitting those in which they

agreed. By means of the aggregate of these comparative

descriptions, I perceived that plants arranged themselves

into classes or families which could not be artificial or

arbitrary, not being founded upon one or two parts, which

might change at certain limits, but on all the parts; so

that the disproportion of one of these parts was corrected

and balanced by the introduction of another.' Thus the

principle of Resemblance {129} was to suffice for the

general arrangement, not by means of a new principle, as

Symmetry or Organization, which should regulate its

application, but by a numeration of the peculiarities in

which the resemblance consisted.

[Note 27\8: Pref. p. clvii.]

[Note 28\8: 'Leur manière de s'engainer.']

The labour which Adanson underwent in the execution of this

thought was immense. By taking each Organ, and considering

its situation, figure, number, &c., he framed sixty-five

Artificial Systems; and collected his Natural Families by a

numerical combination of these. For example, his

_sixty-fifth_ Artificial System[29\8] is that which depends

upon the situation of the Ovary with regard to the Flower;

according to this system he frames _ten_ Artificial Classes,

including _ninety-three_ Sections: and of these Sections the

resulting Natural Arrangement retains _thirty-five_, above

one-third: the same estimate is applied in other cases.

[Note 29\8: Adanson, Pref. p. cccxii.]

But this attempt to make Number supply the defects which the

vague notion of Resemblance introduces, however ingenious,

must end in failure. For, as Decandolle observes[30\8], it

supposes that we know, not only all the Organs of plants,

but all the points of view in which it is possible to

consider them; and even if this assumption were true, which

it is not, and must long be very far from being, the

principle is altogether vicious; for it supposes that all

these points of view, and all the resulting artificial

systems are of equal importance:--a supposition manifestly

erroneous. We are thus led back to the consideration of the

_Relative Importance_ of Organs and their qualities, as a

basis for the classification of plants, which no Artificial

Method can supersede; and thus we find the necessity of

attending to something besides mere external and detached

Resemblance. The method of General Comparison cannot, any

more than the method of Blind Trial, lead us, with any

certainty or clearness, to the Natural Method. Adanson's

Families are held by the best botanists to be, for the

greater part, Natural; but his hypotheses are unfounded; and

his success is {130} probably more due to the dim feeling of

Affinity, by which he was unconsciously guided, than to the

help he derived from his numerical processes.

[Note 30\8: Dec. _Theor. Elem._ p. 67.]

In a succeeding chapter I shall treat of that Natural

Affinity on which a Natural System must really be founded.

But before proceeding to this higher subject, we must say a

few words on some of the other parts of the philosophy of

Natural History,--the Gradation of Groups, the Nomenclature,

the Diagnosis, and the application of the methods to other

subjects.

SECT. V.--_Gradation of Groups._

15. It has been already noticed (last chapter,) that even

that vague application of the idea of resemblance which

gives rise to the terms of common language, introduces a

subordination of classes, as _man_, _animal_, _body_,

_substance_. Such a subordination appears in a more precise

form when we employ this idea in a scientific manner as we

do in Natural History. We have then a series of divisions,

each inclusive of the lower ones, which are expressed by

various metaphors in different writers. Thus some have gone

as far as eight terms of the series[31\8], and have taken,

for the most part, military names for them; as _Hosts_,

_Legions_, _Phalanxes_, _Centuries_, _Cohorts_, _Sections_,

_Genera_, _Species_. But the most received series is

_Classes_, _Orders_, _Genera_, and _Species_; in which,

however, we often have other terms interpolated, as

_Sub-genera_, or Sections of genera. The expressions

_Family_ and _Tribe_, are commonly appropriated to natural

groups; and we speak of the Vegetable, Animal, Mineral

_Kingdom_; but the other metaphors of Provinces, Districts,

&c., which this suggests, have not been commonly used[32\8].

[Note 31\8: Adanson, p. cvi.]

[Note 32\8: _Sub-Kingdom_ has recently been employed by

some naturalists.]

It will of course be understood that each ascending step of

classification is deduced by the same process from the one

below. A Genus is a collection of Species which resemble

each other more than they {131} resemble other species; an

Order is a collection of Genera having, in like manner, the

first degree of resemblance, and so on. How close or how

wide the Degrees of Resemblance are, must depend upon the

nature of the objects compared, and cannot possibly be

prescribed beforehand. Hence the same term, _Class_ and

_Order_ for instance, may imply, in different provinces of

nature, very different degrees of resemblance. The Classes

of Animals are Insects, Birds, Fish, Beasts, &c. The Orders

of Beasts are _Ruminants_, _Tardigrades_, _Plantigrades_,

&c. The two Classes of Plants (according to the Natural

Order[33\8]) are _Vascular_ and _Cellular_, the latter

having neither sexes, flowers, nor spiral vessels. The

Vascular Plants are divided into Orders, as _Umbelliferæ_,

_Ranunculaceæ_, &c.; but between this Class and its Orders

are interposed two other steps:--two Sub-classes,

_Dicotyledonous_ and _Monocotyledonous_, and two Tribes of

each: _Angiospermiæ_, _Gymnospermiæ_ of the first; and

_Petaloideæ_, _Glumaciæ_ of the second. Such interpolations

are modifications of the general formula of subordination,

for the purpose of accommodating it to the most prominent

natural affinities.

[Note 33\8: Lindley.]

16. _Species._--As we have already seen in tracing the

principles of the Natural Method, when by the intimate study

of plants we seek to give fixity and definiteness to the

notion of resemblance and affinity on which all these

divisions depend, we are led to the study of Organization

and Analogy. But we make a reference to physiological

conditions even from the first, with regard to the lowest

step of our arrangement, the _Species_; for we consider it a

proof of the impropriety of separating two Species, if it be

shown that they can by any course of propagation, culture,

and treatment, the one pass into the other. It is in this

way, for example, that it has been supposed to be

established that the common Primrose, Oxlip, Polyanthus, and

Cowslip, are all the same species. Plants which thus, in

virtue of external circumstances, as soil, {132} exposure,

climate, exhibit differences which may disappear by changing

the circumstances, are called _Varieties_ of the species.

And thus we cannot say that a Species is a collection of

individuals which possess the First Degree of Resemblance;

for it is clear that a primrose resembles another primrose

more than it does a cowslip; but this resemblance only

constitutes a Variety. And we find that we must necessarily

include in our conception of Species, the notion of

propagation from the same stock. And thus a Species has been

well defined[34\8]: 'The collection of the individuals

descended from one another, or from common parents, and of

those which resemble these as much as these resemble each

other.' And thus the sexual doctrine of plants, or rather

the consideration of them as things which propagate their

kind, (whether by seed, shoot, or in any other way,) is at

the basis of our classifications.

[Note 34\8: Cuv. _Règne Animal_, p. 19.]

17. The First permanent Degree of Resemblance among

organized beings is thus that which depends on this relation

of generation, and we might expect that the groups which are

connected by this relation would derive their names from the

notion of generation. It is curious that both in Greek and

Latin languages and in our own, the words which have this

origin (γένος, _genus_, _kind_,) do not, in the phraseology

of science at least, denote the nearest degree of

relationship, but have other terms subordinate to them,

which appear etymologically to indicate a mere resemblance

of appearance (εἶδος, _species_, _sort_); and these latter

terms are appropriated to the groups resulting from

propagation. Probably the reason of this is, that the former

terms (_genus_, &c.) had been applied so widely and loosely

before the scientific fixation of terms, that to confine

them to what we call _species_ would have been to restrict

them in a manner too unusual to be convenient.

18. _Varieties. Races._--The Species, as we have said, is

the collection of individuals which resemble each other as

much as do the offspring of a common {133} stock. But within

the limits of this boundary, there are often observable

differences permanent enough to attract our notice, though

capable of being obliterated by mixture in the course of

generation. Such different groups are called _Varieties_.

Thus the Primrose and Cowslip, as has been stated above, are

found to be varieties of the same plant; the Poodle and the

Greyhound are well marked varieties of the species _dog_.

Such differences are hereditary, and it may be long doubtful

whether such hereditary differences are varieties only, or

different species. In such cases the term _Race_ has been

applied.

SECT. VI.--_Nomenclature._

19. The Nomenclature of any branch of Natural History is the

collection of names of all its species; which, when they

become extremely numerous, requires some artifice to make it

possible to recollect or apply them. The known species of

plants, for example, were 10,000 at the time of Linnæus, and

are now probably 60,000. It would be useless to endeavour to

frame and employ separate names for each of these species.

The division of the objects into a subordinated system of

classification enables us to introduce a Nomenclature which

does not require this enormous number of names. The artifice

employed to avoid this inconvenience is to name a Species by

means of two (or it might be more) steps of the successive

division. Thus in Botany, each of the genera has its name,

and the species are marked by the addition of some epithet

to the name of the genus. In this manner about 1,700 generic

names, with a moderate number of specific names, were found

by Linnæus sufficient to designate with precision all the

species of vegetables known at his time. And this _Binary

Method_ of Nomenclature has been found so convenient that it

has been universally adopted in every other department of

the Natural History of organized beings.

Many other modes of Nomenclature have been tried, but no

other has at all taken root. Linnæus himself {134} appears

at first to have intended marking each species by the

Generic Name accompanied by a characteristic Descriptive

Phrase; and to have proposed the employment of a _trivial_

Specific Name, as he termed it, only as a method of

occasional convenience. The use of these _trivial names_,

has, however, become universal, as we have said, and is by

many persons considered the greatest improvement introduced

at the Linnæan reform.

Both Linnæus and other writers (as Adanson) have given many

maxims with a view of regulating the selection of generic

and specific names. The maxims of Linnæus were intended as

much as possible to exclude barbarism and confusion, and

have, upon the whole, been generally adopted; though many of

them were objected to by his contemporaries (Adanson and

others[35\8]), as capricious or unnecessary innovations.

Many of the names, introduced by Linnæus, certainly appear

fanciful enough: thus he gives the name of _Bauhinia_ to a

plant with leaves in pairs, because the Bauhins were a pair

of brothers; _Banisteria_ is the name of a climbing plant,

in honour of Banister, who travelled among mountains. But

such names, once established by adequate authority, lose all

their inconvenience, and easily become permanent; and hence

the reasonableness of the Linnæan rule[36\8], that as such a

perpetuation of the names of persons by the names of plants

is the only honour botanists have to bestow, it ought to be

used with care and caution.

[Note 35\8: Pp. cxxix. clxxii.]

[Note 36\8: _Phil Bot._ s. 239.]

The generic name must, as Linnæus says, be fixed[37\8]

before we attempt to form a specific name; 'the latter

without the former is like the clapper without the bell.'

The name of the genus being established, the species may be

marked by adding to it 'a single word taken at will from any

quarter;' that is, not involving a description or any

essential property of the plant, but a casual or arbitrary

appellation[38\8]. Thus the {135} various species of

_Hieracium_[39\8] are _Hieracium Alpinum_, _H. Halleri_, _H.

Pilosella_, _H. dubium_, _H. murorum_, &c. where we see how

different may be the kind of origin of the words.

[Note 37\8: _Ib._ s. 222.]

[Note 38\8: _Ib._ s. 260.]

[Note 39\8: Hooker, _Fl. Scot._ 228.]

Attempts have been made at various times to form the name of

species from those of genera in some more symmetrical

manner. Thus some have numbered the species of genus, 1, 2,

3, &c.; but this method is liable to the inconveniences,

first, that it offers nothing for the memory to take hold

of; and second, that if a new species intermediate between 1

and 2, 2 and 3, &c., be discovered, it cannot be put in its

place. It has also been proposed to mark the species by

altering the termination of the genus. Thus Adanson[40\8],

denoting a genus by the name _Fonna_ (_Lychnidea_),

conceived he might mark five of its species by altering the

last vowel, _Fonna_, _Fonna-e_, _Fonna-i_, _Fonna-o_,

_Fonna-u_; then others by _Fonna-ha_, _Fonna-ka_, and so on.

This course would be liable to the same evils which have

been noticed as belonging to the numerical method.

[Note 40\8: Pref. clxxvi.]

The names of plants (and the same is true of animals) have

in common practice been binary only, consisting of a generic

and a specific name. The Class and Order have not been

admitted to form part of the appellation of the species.

Indeed it is easy to see that a name which must be identical

in so many instances as that of an Order would be, would be

felt as superfluous and burdensome. Accordingly, Linnæus

makes it a precept[41\8], that the name of the Class and the

Order must not be expressed but understood: and hence, he

says, Royen, who took _Lilium_ for the name of a Class,

rightly rejected it as a generic name, and substituted

_Lirium_, with the Greek termination.

[Note 41\8: _Phil. Bot._ s. 215.]

Yet we must not too peremptorily assume such maxims as these

to be universal for all classificatory sciences. It is very

possible that it may be found advisable to use _three_

terms, that of order, genus and {136} species, in

designating minerals, as is done in Mohs's nomenclature; for

example, _Rhombohedral Calc Haloide_, _Paratomous Hal

Baryte_.

It is possible also that it may be found useful in the same

science to mark some of the steps of classification by the

termination. Thus it has been proposed to confine the

termination _ite_ to the Order _Silicides_ of Naumann, as

Apophyll_ite_, Stilb_ite_, Leuc_ite_, &c., and to use names

of different form in other orders, as Talc _Spar_ for

Brennerite, Pyramidal Titanium _Oxide_ for Octahedrite. Some

such method appears to be the most likely to give us a

tolerable mineralogical nomenclature.

SECT. VII.--_Diagnosis._

20. German Naturalists speak of a part of the general method

which they call the _Characteristik_ of Natural History, and

which is distinguished from the _Systematik_ of the science.

The _Systematick_ arranges the objects by means of all their

resemblances, the _Characteristick_ enables us to detect

their place in the arrangement by means of a few of their

characters. What these characters are to be, must be

discovered by observation of the groups and divisions of the

system when they are formed. To construct a collection of

such characters as shall be clear and fixed, is a useful,

and generally a difficult task; for there is usually no

apparent connexion between the marks which are used in

discriminating the groups, and the nature of the groups

themselves. They are assumed only because the naturalist,

extensively and exactly acquainted with the groups and the

properties of the objects which compose them, sees, by a

survey of the field, that these marks divide it properly.

The Characteristick has been termed by some English

Botanists the _Diagnosis_ of plants; a word which we may

conveniently adopt. The Diagnosis of any genus or species is

different according to the system we follow. Thus in the

Linnæan System the Diagnosis of the Rose is in the first

place given by its Class and Order: it is {137} Icosandrous,

and Polygynous; and then the Generic Distinction is that the

calyx is five-cleft, the tube urceolate, including many

hairy achenia, the receptacle villous[42\8]. In the Natural

System the Rose-Tribe are distinguished as being[43\8]

'Polypetalous dicotyledons, with lateral styles, superior

simple ovaria, regular perigynous stamens, exalbuminous

definite seeds, and alternate stipulate leaves.' And the

true Roses are further distinguished by having 'Nuts,

numerous, hairy, terminated by the persistent lateral style

and inclosed within the fleshy tube of the calyx,' &c.

[Note 42\8: Lindley, _Nat. Syst._ p. 149.]

[Note 43\8: _Ib._ pp. 81, 3.]

It will be observed that in a rigorous Artificial System the

_Systematick_ coincides with the _Characteristick_; the

_Diataxis_ with the _Diagnosis_; the reason why a plant is

put in a division is identical with the mode by which it is

known to be in the division. The Rose is in the class

_icosandria_, because it has many stamens inserted in the

calyx; and when we see such a set of stamens we immediately

know the class. But this is not the case with the Diagnosis

of Natural Families. Thus the genera _Lamium_ and

_Galeopsis_ (Dead Nettle and Hemp Nettle) are each formed

into a separate group in virtue of their general

resemblances and differences, and not because the former has

one tooth on each side of the lower lip, and the latter a

notch in its upper lip, though they are distinguished by

these marks.

Thus so far as our Systems are natural, (which, as we have

shown, all systems to a certain extent must be), the

Characteristick is distinct both from a Natural and an

Artificial System; and is, in fact, an Artificial Key to a

Natural System. As being Artificial, it takes as few

characters as possible; as being Natural, its characters are

not selected by any general or prescribed rule, but follow

the natural affinities. The Botanists who have made any

steps in the formation of a natural method of plants since

Linnæus, have all attempted to give a Diagnosis

corresponding to the Diataxis of their method.

{{138}}

CHAPTER III.

APPLICATION OF THE NATURAL HISTORY METHOD TO MINERALOGY.

1. THE philosophy of the Sciences of Classification has had

great light thrown upon it by discussions concerning the

methods which are used in Botany: for that science is one of

the most complete examples which can be conceived of the

consistent and successful application of the principles and

ideas of Classification; and this application has been made

in general without giving rise to any very startling

paradoxes, or disclosing any insurmountable difficulties.

But the discussions concerning methods of Mineralogical

Classification have been instructive for quite a different

reason: they have brought into view the boundaries and the

difficulties of the process of Classification; and have

presented examples in which every possible mode of

classifying appeared to involve inextricable contradictions.

I will notice some of the points of this kind which demand

our attention, referring to the works published recently by

several mineralogists.

In the History of Mineralogy we noticed the attempt made by

Mohs and other Germans to apply to minerals a method of

arrangement similar to that which has been so successfully

employed for plants. The survey which we have now taken of

the grounds of that method will point out some of the

reasons of the very imperfect success of this attempt. We

have already said that the _Terminology_ of Mineralogy was

materially reformed by Werner; and including in this branch

of the subject (as we must do) the Crystallography of later

writers, it may be considered as to a great extent complete.

Of the attempts at a Natural arrangement, that of Mohs

appears to proceed by the {139} method of _blind trial_, the

undefinable perception of relationship, by which the

earliest attempts at a Natural Arrangement of plants were

made. Breithaupt however, has made (though I do not know

that he has published) an essay in a mode which corresponds

very nearly to Adanson's process of _multiplied

comparisons_. Having ascertained the specific gravity and

hardness of all the species of minerals, he arranged them in

a table, representing by two lines at right angles to each

other these two numerical quantities. Thus all minerals were

distributed according to two co-ordinates representing

specific gravity and hardness. He conceived that the groups

which were thus brought together were natural groups. On

both these methods, and on all similar ones, we might

observe, that in minerals as in plants, the mere general

notion of Likeness cannot lead us to a real arrangement:

this notion requires to have precision and aim given it by

some other relation;--by the relation of Chemical

Composition in minerals, as by the relation of Organic

Function in vegetables. The physical and crystallographical

properties of minerals must be studied with reference to

their constitution; and they must be arranged into Groups

which have some common Chemical Character, before we can

consider any advance as made towards a Natural Arrangement.

In reality, it happens in Mineralogy as it happened in

Botany, that those speculators are regulated by an obscure

perception of this ulterior relation, who do not profess to

be regulated by it. Several of the Orders of Mohs have

really great unity of chemical character, and thus have good

evidence of their being really Natural Orders.

2. Supposing the Diataxis of minerals thus obtained, Mohs

attempted the Diagnosis; and his _Characteristick of the

Mineral Kingdom_, published in Dresden, in 1820, was the

first public indication of his having constructed a system.

From the nature of a Characteristick, it is necessarily

brief, and without any ostensible principle; but its

importance was duly appreciated by the author's countrymen.

Since that {140} time, many attempts have been made at

improved arrangements of minerals, but none, I think,

(except perhaps that of Breithaupt,) professing to proceed

rigorously on the principles of Natural History;--to arrange

by means of external characters, neglecting altogether, or

rather postponing, the consideration of chemical properties.

By relaxing from this rigour, however, and by combining

physical and chemical considerations, arrangements have been

obtained (for example, that of Naumann,) which appear more

likely than the one of Mohs to be approximations to an

ultimate really natural system. Naumann's Classes are

_Hydrolytes_, _Haloides_, _Silicides_, _Metal Oxides_,

_Metals_, _Sulphurides_, _Anthracides_, with subdivisions of

Orders, as _Anhydrous unmetallic Silicides_. It may be

remarked that the designations of these are mostly chemical.

As we have observed already, Chemistry, and Mineralogy in

its largest sense, are each the necessary supplement of the

other. If Chemistry furnish the Nomenclature, Mineralogy

must supply the Physiography: if the Arrangement be founded

on External Characters and the Names be independent of

Chemistry, the chemical composition of each species is an

important scientific Truth respecting it.

3. The inquiry may actually occur, whether any subordination

of groups in the mineral kingdom has really been made out.

The ancient chemical arrangements, for instance, that of

Haüy, though professing to distribute minerals according to

Classes, Orders, Genera, and Species, were not only

arbitrary, but inapplicable; for the first postulate of any

method, that the species should have constant characters of

unity and difference, was not satisfied. It was not

ascertained that carbonate of lime was really

distinguishable in all cases from carbonate of magnesia, or

of iron; yet these species were placed in remote parts of

the system: and the above carbonates made just so many

species; although, if they were distinct from one another at

all, they were further distinguishable into additional

species. Even now, we may, perhaps, say that the limits of

mineralogical species, and their laws of fixity, are {141}

not yet clearly seen. For the discoveries of the isomorphous

relations and of the optical properties of minerals have

rather shown us in what direction the object lies, than led

us to the goal. It is clear that, in the mineral kingdom,

the Definition of Species, borrowed from the laws of the

continuation of the kind, which holds throughout the organic

world, fails us altogether, and must be replaced by some

other condition: nor is it difficult to see that the

definite atomic relations of the chemical constituents, and

the definite crystalline angle, must supply the principles

of the _Specific_ Identity for minerals. Yet the exact

limits of definiteness in both these cases (when we admit

the effect of mechanical mixtures, &c.) have not yet been

completely disentangled. Moreover, any _arbitrary_

assumption (as the allowance of a certain per-centage of

mixture, or a certain small deviation in the angle,) is

altogether contrary to the philosophy of the Natural System,

and can lead to no stable views. It is only by laborious,

extensive, and minute research, that we can hope to attain

to any solid basis of arrangement.

4. Still, though there are many doubts respecting

mineralogical species, a large number of such species are so

far fixed that they may be supposed capable of being united

under the higher divisions of a system with approximate

truth. Of these higher divisions, those which have been

termed _Orders_ appear to tend to something like a fixed

chemical character. Thus the _Haloids_ of Naumann, and

mostly those of Mohs, are combinations of an oxide with an

acid, and thus resemble Salts, whence their name. The

Silicides contain most of Mohs's _Spaths_: and the Orders

_Pyrites_, _Glance_, and _Blende_, are common to Naumann and

Mohs; being established by the latter on a difference of

external character, which difference is, indeed, very

manifest; and being included by the former in one chemical

_Class_, _Sulphurides_. The distinctions of _Hydrous_ and

_Anhydrous_, _Metallic_ and _Unmetallic_, are, of course,

chemical distinctions, but occur as the differences of

Orders in Naumann's mixed system. {142}

We may observe that some French writers, following Haüy's

last edition, use, instead of _metallic_ and _unmetallic_,

_autopside metallic_ and _heteropside metallic_; meaning by

this phraseology to acknowledge the discovery that earths,

etc., _are_ metallic, though they do not _appear_ to be so,

while metals both are and appear metallic. But this seems to

be a refinement not only useless but absurd. For what is

gained by adding the word _metallic_, which is common to

all, and therefore makes no distinction? If certain metals

are distinguished by their _appearing_ to be metals, this

appearance is a reason for giving them the peculiar name,

_metals_. Nothing is gained by first bringing earths and

metals together, and then immediately separating them again

by new and inconvenient names. No proposition can be

expressed better by calling _earths_, _heteropside metallic

substances_, and therefore such nomenclature is to be

rejected.

Granting, then, that the Orders of the best recent

mineralogical systems approximate to natural groups, we are

led to ask whether the same can be said of the Genera of the

Natural History systems, such as those of Mohs and

Breithaupt. And here I must confess that I see no principle

in these Genera; I have failed to apprehend the conceptions

by the application of which they have been constructed: I

shall therefore not pass any further judgment upon them. The

subordination of Mineralogical Species to Orders is a

manifest gain to science: in the interposition of Genera I

see nothing but a source of confusion.

5. In Mineralogy, as in other branches of natural history, a

reformed arrangement ought to give rise to a reformed

Nomenclature; and for this, there is more occasion at

present in Mineralogy than there was in Botany at the worst

period, at least as far as the extent of the subject allows.

The characters of minerals are much more dimly and

unfrequently developed than those of plants; hence arbitrary

chemical arrangements, which could not lead to any natural

groups, and therefore not to any good names, prevailed till

recently; and this state of things produced an anarchy {143}

in which every man did what seemed right in his own

eyes,--proposed species without any ascertained distinction,

and without a thought of subordination, and gave them

arbitrary names; and thus with only about two or three

hundred known species, we have thousands upon thousands of

names, of anomalous form and uncertain application.

Mohs has attempted to reform the Nomenclature of the subject

in a mode consistent with his attempt to reform the System.

In doing this, he has fatally transgressed a rule always

insisted upon by the legislators of Botany, of altering

usual names as little as possible; and his names are both so

novel and so cumbrous, that they appear to have little

chance of permanent currency. They are, perhaps, more

unwieldy than they need to be, by referring, as we have

said, to three of the steps of his classification, the

Species, Genus, and Order. We may, however, assert

confidently, from the whole analogy of natural history, that

no good names can be found which do not refer to at least

_two_ terms of the arrangement. This rule has been

practically adopted to a great extent by Naumann, who gives

to most of his Haloids the name _Spar_, as Calc spar, Iron

spar, &c.; to all his Oxides the terminal word _Erz_

(_Ore_); and to the species of the orders _Kies_

(_Pyrites_), _Glance_, and _Blende_, these names. It has

also been theoretically assented to by Beudant, who proposes

that we should say _silicate stilbite_, _silicate chabasie_;

_carbonate calcaire_, _carbonate witherite_; _sulphate

couperose_, &c. One great difficulty in this case would

arise from the great number of _silicides_; it is not likely

that any names would obtain a footing which tacked the term

_silicide_ to another word for each of these species. The

artifice which I have proposed, in order to obviate this

difficulty, is that we should make the names of the

silicides, and those alone, end in _ite_ or _lite_, which a

large proportion of them do already.

By this and a few similar contrivances, we might, I

conceive, without any inconvenient change, introduce into

Mineralogy a systematic nomenclature. {144}

6. I shall now proceed to make a few remarks on a work on

Mineralogy more recent than those which I have above

noticed, and written with express reference to such

difficulties as I have been discussing. I allude to the

treatise of M. Necker, _Le Règne Mineral ramené aux Methods

d'Histoire Naturelle_[44\8], which also contains various

dissertations on the Philosophy of Classification in

general, and its application to Mineralogy in particular.

[Note 44\8: Paris, 1835.]

M. Necker remarks very justly, that Mineralogy, as it has

hitherto been treated, differs from all other branches of

Natural History in this:--that while it is invested with all

the forms of the sciences of classification,--Classes,

Divisions, Genera, and the like,--the properties of those

bodies to which the mineralogical student's attention is

directed have no bearing whatever on the classification. A

person, he remarks[45\8], might be perfectly well acquainted

with all the characters of minerals which Werner or Haüy

examined so carefully, and might yet be quite unable to

assign to any mineral its place in the divisions of their

methods. There is[46\8] a complete separation between the

study of mineralogical characters and the recognition of the

name and systematic place of a mineral. Those who know

_mineralogy_ well, may know _minerals_ ill, or hardly at

all; the systematist may be in such knowledge vastly

inferior to the mineral-dealer or the miner. In this respect

there is a complete contrast between this science and other

classificatory sciences.

[Note 45\8: _Règne Mineral_, p. 3.]

[Note 46\8: _Ib._ p. 8.]

Again, in the best-known systems of Mineralogy, (as those of

Werner and Haüy,). the bodies which are grouped together as

belonging to the same division, have not, as they have in

other classificatory sciences, any resemblance. The

different members of the larger classes are united by the

common possession of some abstract property,--as, that they

all contain iron. This is a property to which no common

circumstance in the bodies themselves corresponds. What is

there common to the minerals named oxidulous iron, sulphuret

{145} of iron, carbonate of iron, sulphate of iron, except

that they all contain iron? And when we have classed these

bodies together, what general assertion can we make

concerning them, except that which is the ground of our

classification, that they contain iron? They have nothing in

common with iron or with each other in any other way.

Again, as these classes have no general properties, all the

properties are particular to the species; and the

descriptions of these necessarily become both tediously

long, and inconveniently insulated.

7. These inconveniences arise from making Chemical

Composition the basis of Mineralogical Classification

without giving Chemical Analysis the first place among

Mineral Properties. Shall we, then, correct this omission,

so far as it has affected mineralogical systems? Shall we

teach the student the chemical analysis of minerals, and

then direct him to classify them according to the results of

his analysis[47\8]?

[Note 47\8: _Règne Mineral_, p. 18.]

But why should we do this? To what purpose, or on what

ground, do we arrange the results of chemical analysis

according to the forms and subordination of natural history?

Is not Chemistry a science distinct from Natural History?

Are not the sciences opposed? Is not natural history

confined to organic bodies? Can mere chemical elements and

their combinations be, with any propriety or consistency,

arranged into Species, Genera, and Families? What is the

principle on which genera and species depend? Do not Species

imply Individuals? What is an Individual in the case of a

chemical substance?

8. We thus find some of the widest and deepest questions of

the philosophy of classification brought under our

consideration when we would provide a method for the

classification of minerals. The answers to these questions

are given by M. Necker; and I shall state some of his

opinions; taking the liberty of adding such remarks as are

suggested by referring the subject {146} to those principles

which have already been established in this work.

M. Necker asserts[48\8] that the distinctions of different

Sciences depend, not on the objects they consider, but on

the different and independent points of view on which they

proceed. Each science has its logic, that is, its mode of

applying the general rules of human reason to its own

special case. It has been said by some[49\8], that in

minerals, natural history and chemistry contemplate common

objects, and thus form a single science. But do chemistry

and natural history consider minerals in the same point of view?

[Note 48\8: _Règne Mineral_, p. 23.]

[Note 49\8: _Ib._ p. 27.]

The answer is, that they do not. Physics and Chemistry

consider the properties of bodies in an abstract manner; as,

their composition, their elements, their mutual actions,

with the laws of these; their forces, as attraction,

affinity; all which objects are abstract ideas. In these

cases we have nothing to do with bodies themselves, but as

the vehicles of the powers and properties which we

contemplate.

Natural History, on the other hand, has to do with natural

bodies: their properties are not considered abstractedly,

but only as characters. If the properties are abstracted, it

is but for a moment. Natural history has to describe and

class bodies as they are. All which cannot be perceived by

the senses, belongs not to its domain, as molecules, atoms,

elements.

Natural history[50\8] may have recourse to physics or

chemistry in order to recognize those properties of bodies

which serve as characters; but natural history is not, on

that account, physics or chemistry. Classification is the

essential business of the natural historian[51\8], to which

task chemistry and physics are only instrumental, and the

further account of properties only complementary.

[Note 50\8: _Ib._ p. 37.]

[Note 51\8: _Ib._ p. 41.]

It has been said, in support of the doctrine that chemistry

and mineralogy are identical, that chemistry does not

neglect external characters. 'The chemist in {147}

describing sulphur, mentions its colour, taste, odour,

hardness, transparence, crystalline form, specific gravity;

how does he then differ from the mineralogist?' But to this

it is replied, that these notices of the external characters

of this or any substance are introduced in chemistry merely

as convenient marks of recognition; whereas they are

essential in mineralogy. If we had taken the account given

of several substances instead of one, we should have seen

that the chemist and the naturalist consider them in ways

altogether different. The chemist will make it his business

to discover the mutual action of the substances; he will

combine them, form new products, determine the proportions

of the elements. The mineralogist will divide the substances

into groups according to their properties, and then

subdivide these groups, till he refers each substance to its

species. Exterior and physical characters are merely

accessory and subordinate for the chemist; chemistry is

merely instrumental for the mineralogist.

This view agrees with that to which we have been led by our

previous reasonings; and may, according to our principles,

be expressed briefly by saying, that the Idea which

Chemistry has to apply is the Idea of Elementary

Composition, while Natural History applies the Idea of

Graduated Resemblances, and thus performs the task of

classification.

9. The question occurs[52\8], whether Natural History can be

applied to Inorganic Substances? And the answer to this

question is, that it can be applied, if there are such

things as inorganic individuals, since the resemblances and

differences with which natural history has to do are the

resemblances and differences of individuals.

[Note 52\8: _Règne Mineral_, p. 46.]

What is an Individual? It certainly is not that which is so

simple that it cannot be divided. Individual animals are

composed of many parts. But if we examine, we shall find

that our Idea of an Individual is, that it is a whole

composed of parts, which {148} are not similar to the whole,

and have not an independent existence, while the whole has

an independent existence and a definite form[53\8].

[Note 53\8: _Règne Mineral_, p. 52.]

What then is the Mineralogical Individual? At first, while

minerals were studied for their use, the most precious of

the substances which they contained was looked upon as the

characteristic of the mineral. The smallest trace of silver

made a mineral an _ore of silver_. Thus forms and properties

were disregarded, and _substance_ was considered as

identical with _mineral_. And hence[54\8] Daubenton refused

to recognize _species_ in the mineral kingdom, because he

recognized no individuals. He proposed to call _sorts_ what

we call species. In this way of considering minerals, there

are no individuals.

[Note 54\8: _Ib._ p. 54.]

10. But still this is not satisfactory: for if we take a

well-formed and distinct crystal, this clearly _is_ an

individual[55\8].

[Note 55\8: _Ib._ p. 56.]

It may be objected, that the crystal is divisible (according

to the theory of crystallography) into smaller solids; that

these small solids are really the simple objects; and that

actual crystals are formed by combinations of these

molecules according to certain laws.

But, as we have already said, an individual is such, not

because it cannot be divided, but because it cannot be

divided into parts similar to the whole. As to the division

of the form into its component _laws_, this is an abstract

proceeding, foreign to natural history[56\8]. Therefore

there is so far nothing to prevent a crystal from being an

individual.

[Note 56\8: _Ib._ p. 58.]

11. We cannot (M. Necker goes on to remark) consider the

_Integrant Molecules_ as individuals. These are useful

abstractions, but abstractions only, which we must not deal

with as real objects. Haüy himself warns us[57\8] that his

doctrine of increments is a purely abstract conception, and

that nature, in fact, follows a different process.

Accordingly, Weiss and Mohs express laws identical with

those of Haüy, without even {149} speaking of molecules; and

Wollaston and Davy have deemed it probable that the

molecules are not polyhedrons, but spheres or spheroids.

Such mere creations of the mind can never be treated as

individuals. If the maxim of natural history,--that the

Species is a collection of Individuals--be applied so as to

make those individuals mere abstractions; or if, instead of

Individuals, we take such an abstraction as Substance or

Matter, the course of natural history is altogether

violated. And yet this errour has hitherto generally

prevailed; and mineralogists have classified, not things,

but abstract ideas[58\8].

[Note 57\8: _Ib._ p. 61.]

[Note 58\8: _Règne Mineral_, p. 67.]

12. But it may be said[59\8], will not the small solids

obtained by Cleavage better answer the idea of individuals?

To this it is replied, that these small solids have no

independent existence. They are only the result of a mode of

division. They are never found separate and independent. The

secondary forms which they compose are determined by various

circumstances (the nature of the solution, &c.); and the

cleavage which produces these small solids is only one

result among many, from the crystalline forces[60\8].

[Note 59\8: _Ib._ p. 69.]

[Note 60\8: _Ib._ p. 71.]

Thus neither Integrant Molecules, nor Solids obtained by

Cleavage, can be such mineralogical Individuals as the

spirit of natural history requires. Hence it appears that we

must take the real Crystals for Individuals[61\8].

[Note 61\8: _Ib._ p. 73.]

13. We must, however, reject crystals (generally large ones)

which are obviously formed of several smaller ones of a

similar form (as occurs so often in quartz and calc spar).

We must also distinguish cases in which a large regular form

is composed of smaller but different regular forms (as

octahedrons of fluor spar made up of cubes). Here the small

component forms are the individuals. Also we must notice the

cases[62\8] in which we have a natural crystal, similar to

the primary form. Here the face will show whether {150} the

body is a result obtained by cleavage or a natural individual.

[Note 62\8: _Ib._ p. 75.]

14. It will be objected[63\8], that the crystalline form

ought not to be made the dominant character in mineralogy,

since it rarely occurs perfect. To this it is replied, that

even if the application of the principle be difficult, still

it has been shown to be the only true principle, and

therefore we have no alternative. But further[64\8], it is

not true that amorphous substances are more numerous than

crystals. In Leonhard's _Manual of Oryctognosy_, there are

377 mineral substances. Of these, 281 have a crystalline

structure, and 96 only have not been found in a regular form.

[Note 63\8: _Règne Mineral_, p. 79.]

[Note 64\8: _Ib._ p. 82.]

Again, the 281 crystalline forms have each its varieties,

some of which are crystalline, and some are not so. Now the

crystalline varieties amount to 1453, and the uncrystalline

to 186 only. Thus mineralogy, according to the view of it

here presented, has a sufficiently wide field[65\8].

[Note 65\8: _Ib._ p. 84.]

15. It will be objected[66\8], that according to this mode

of proceeding, we must reject from our system all

non-crystalline minerals. But we reply, that if the mass be

composed of crystals, the size of the crystals makes no

difference. Now lamellar and other compact masses are very

generally groups of crystals in various positions.

Individuals mutilated and mixed together are not the less

individuals; and therefore such masses may be treated as

objects of natural history.

[Note 66\8: _Ib._ p. 86.]

If we cannot refer all rocks to crystalline species, those

which elude our method may appear as an appendix,

corresponding to those plants which botanists call _genera

incertæ sedis_[67\8].

[Note 67\8: _Ib._ p. 91.]

But these genera and species will often be afterwards

removed into the crystalline part of the system, by being

identified with crystalline species. Thus _pyrope_, &c.,

have been referred to _garnet_, and _basalt_, {151} _wacke_,

&c., to compound rocks. Thus veins of _Dolerite_, visibly

composed of two or three elements, pass to an apparently

simple state by becoming fine-grained[68\8].

[Note 68\8: _Règne Mineral_, p. 93.]

16. Finally[69\8], we have to ask, are artificial crystals

to enter into our classification? M. Necker answers, No;

because they are the result of art, like mules, mestizos,

hybrids, and the like.

[Note 69\8: _Ib._ p. 95.]

17. Upon these opinions, we may observe, that they appear to

be, in the main, consistent with the soundest philosophy.

That each natural crystal is an individual, is a doctrine

which is the only basis of Mineralogy as a Natural

Historical Science; yet the imperfections and confused

unions of crystals make this principle difficult to apply.

Perhaps it may be expressed in a more precise manner by

referring to the crystalline forces, and to the axes by

which their operation is determined, rather than to the

external form. _That_ portion of a mineral substance is a

mineralogical _individual_ which is determined by

crystalline forces acting to the _same axes_. In this way we

avoid the difficulty arising from the absence of faces, and

enable ourselves to use either cleavage, or optical

properties, or any others, as indications of the identity of

the individual. The individual extends so far as the polar

forces extend by which crystalline form is determined,

whether or not those forces produce their full effect,

namely, a perfectly circumscribed polyhedron.

18. There is only one material point on which our principles

lead us to differ from M. Necker;--the propriety of

including _artificial crystals_ in our mineralogical

classification. To exclude them, as he does, is a conclusion

so entirely at variance with the whole course of his own

reasonings, that it is difficult to conceive that he would

persist in his conclusion, if his attention were drawn to

the question more steadily. For, as he justly says[70\8],

each science has its appropriate domain, determined by its

peculiar point of view. Now artificial and natural crystals

are considered in the same point of view, (namely, with

reference to {152} crystalline, physical, and optical

properties, as subservient to classification,) and ought,

therefore, to belong to the same science. Again, he

says[71\8], that Chemistry would reject as useless all

notice of the physical properties and external characters of

substances, if a _special science_ were to take charge of

the description and classification of these products. But

such a special science must be Mineralogy; for we cannot

well make one science of the classification of natural, and

another of that of artificial substances: or if we do, the

two sciences will be identical in method and principles, and

will extend over each other's boundaries, so that it will be

neither useful nor possible to distinguish them. Again, M.

Necker's own reasonings on the selection of the individual

in mineralogy are supported by well chosen examples[72\8];

but these examples are taken from artificial salts; as, for

instance, common salt crystallizing in different mixtures.

Again, the analogy of mules and mestizos, as products of

art, with chemical compounds, is not just. Chemical

compounds correspond rather to natural species, propagated

by man under the most natural circumstances, in order that

he may study the laws of their production[73\8].

[Note 70\8: _Ib._ p. 23.]

[Note 71\8: _Règne Mineral_, p. 36.]

[Note 72\8: _Ib._ p. 71.]

[Note 73\8: We may remark that M. Necker, in his own

arrangement of minerals, inserts among his species Iron and

Lead, which do not occur Native.]

19. But the decisive argument against the separation of

natural and artificial crystals in our schemes of

classification is, that we _cannot_ make such a separation.

Substances which were long known only as the products of the

laboratory, are often discovered, after a time, in natural

deposits. Are the crystals which are found in a forgotten

retort or solution to be considered as belonging to a

different science from those which occur in a deserted mine?

And are the crystals which are produced where man has turned

a stream of water or air out of its course, to be separated

from natural crystals, when the composition, growth, and

properties, are exactly the same in both? And again: How

many natural crystals can we already produce by {153}

synthesis! How many more may we hope to imitate hereafter!

M. Necker himself states[74\8], that Mitscherlich found, in

the scoriæ of the mines of Sweden and Germany, artificial

minerals having the same composition and the same

crystalline form with natural minerals: as silicates of

iron, lime, and magnesia, agreeing with Peridot; bisilicate

of iron, lime, and magnesia, agreeing with Pyroxene; red

oxide of copper; oxide of zinc; protoxide of iron (_fer

oxydulé_); sulphurets of iron, zinc, lead; arseniuret of

nickel; black mica. These were accidental results of fusion.

But M. Berthier, by bringing together the elements in proper

quantities, has succeeded in composing similar minerals, and

has thus obtained artificial silicates, with the same forms

and the same characters as natural silicates. Other chemists

(M. Haldat, M. Becquerel) have, in like manner, obtained, by

artificial processes, other crystals, known previously as

occurring naturally. How are these crystals, thus identical

with natural minerals, to be removed out of the domain of

mineralogy, and transferred to a science which shall

classify artificial crystals only? If this be done, the

mineralogist will not be able to classify any specimen till

he has human testimony whether it was found naturally

occurring or produced by chemical art. Or is the other

alternative to be taken, and are these crystals to be given

up to mineralogy because they occur naturally also? But what

can be more unphilosophical than to refer to separate

sciences the results of chemical processes closely allied,

and all but identical? The chemist constructs bisilicates,

and these are classified by the mineralogist: but if he

constructs a trisilicate, it belongs to another science. All

these intolerable incongruities are avoided by acknowledging

that artificial, as well as natural, crystals belong to the

domain of mineralogy. It is, in fact, the _name_ only of

_Mineralogy_ which appears to discover any inconsistency in

this mode of proceeding. Mineralogy is the {154}

representative of a science which has a wider office than

mineralogists first contemplated; but which must exist, in

order that the body of science may be complete. There must,

as we have already said, be a Science, the object of which

is to classify bodies by their physical characters, in order

that we may have some means of asserting chemical truths

concerning bodies; some language in which we may express the

propositions which chemical analysis discovers. And this

Science will have its object prescribed, not by any

accidental or arbitrary difference of the story belonging to

each specimen;--not by knowing whether the specimen was

found in the mine or in the laboratory; produced by

attempting to imitate nature, or to do violence to her:--but

will have its course determined by its own character. The

range and boundaries of this Science will be regulated by

the Ideas with which it deals. Like all other sciences, it

must extend to everything to which its principles apply. The

limits of the province which it includes are fixed by the

consideration that it must be a connected whole. No previous

definition, no historical accident, no casual phrase, can at

all stand in the way of philosophical consistency;--can make

this Science exclude what that includes, or oblige it to

admit what that rejects. And thus, whatever we call our

Science;--whether we term it External Chemistry, Mineralogy,

the Natural History of Inorganic Bodies;--since it can be

nothing but the Science of the Classification of Inorganic

Bodies of definite forms and properties, it must classify

all such bodies, whether or not they be minerals, and

whether or not they be natural.

[Note 74\8: _Règne Mineral_, p. 151.]

20. In the application of the principles of classification

to minerals, the question occurs, What are to be considered

as mineral _Species_? By Species we are to understand,

according to the usage of other parts of natural history,

the lowest step of our subordinate divisions;--the most

limited of the groups which have definite distinctions. What

definite distinctions of groups of objects of any kind

really occur in nature, is to be learnt from an examination

of nature: and the {155} result of our inquiries will be

some general principle which connects the members of each

group, and distinguishes the members of groups which, though

contiguous, are different. In the classification of

organized bodies, the rule which thus presides over the

formation of Species is the principle of _reproduction_.

Those animals and those plants are of the same Species which

are produced from a common stock, or which resemble each

other as much as the progeny of a common stock. Accordingly

in practice, if any questions arise whether two varieties of

form in organic things be of the same or different species,

it is settled by reference to the fact of reproduction; and

when it is ascertained that the two forms come within the

habitual and regular limits of a common circle of

reproduction, they are held to be of the same species. Now

in crystals, this principle of reproduction disappears

altogether, and the basis of the formation of species must

be sought elsewhere. We must have some other principle to

replace the reproduction which belongs only to organic life.

This principle will be, we may expect, one which secures the

permanence and regularity of mineral forms, as the

reproductive power does of animal and vegetable. Such a

principle is the _Power of Crystallization_. The forces of

which solidity, cohesion, and crystallization are the

result, are those which give to minerals their permanent

existence and their physical properties; and ever since the

discovery of the distinctions of Crystalline Forms and

Crystalline Systems, it is certain that this force

distinguishes groups of crystals in the most precise and

definite manner. The rhombohedral carbonates of lime and of

iron, for instance, are distinguished exactly by the angles

of their rhombohedrons. And if, in the case of any proposed

crystal, we should doubt to which kind the specimen belongs,

the measurement of the angles of cleavage would at once

decide the question. The principle of Crystallization

therefore appears, from analogy, to be exactly fitted to

take the place of the principle of organic Generation. The

forces which make the individual permanent and its

properties definite, here stand in the place of the forces

{156} which preserve the race, while individuals are

generated and die.

21. According to this view, the different Modifications of

the _same_ crystalline form would be _Varieties_ only of the

same Species. All the various solids, for example, which are

produced by the different laws of derivation of rhombohedral

carbonate of lime, would fall within the same Species. And

this appears to be required by the general analogy of

Natural History. For these differences of form, produced by

the laws of crystalline derivation, are not _definite_. The

faces which are added to one form in order to produce

another, may be of any size, small or large, and thus the

crystal which represents one modification passes by

insensible degrees to another. The forms of calc spar, which

we call _dog-tooth spar_, _cannon spar_, _nail-head spar_,

and the like, appear at first, no doubt, distinct enough;

but so do the races of dogs. And we find, in the mineral as

in the animal, that the distinction is obliterated by taking

such intermediate steps as really occur. And if a _fragment_

of any of these crystals is given us, we can determine that

it is rhombohedral carbonate of lime; but it is not

possible, in general, to determine to which of the kinds of

crystals it has belonged.

22. Notwithstanding these considerations, M. Necker has

taken for his basis of mineral species[75\8] the _Secondary_

Modifications, and not the Primary Forms. Thus _cubical

galena_, _octahedral galena_, and _triform galena_, are,

with him, three _species_ of crystals.

[Note 75\8: _Règne Mineral_, p. 396.]

On this I have to observe, as I have already done, that on

this principle we have no _definite_ distinction of species;

for these forms may and do pass into each other: among

cubo-octahedrons of galena occur cubes and octahedrons, as

one face or another vanishes, and the transition is

insensible. We shall, on this principle, find almost always

three or four species in the same tuft of crystals; for

almost every individual in such assemblages may exhibit a

different combination of {157} secondary faces. Again, in

cases where the secondary laws are numerous, it would be

impracticable to enumerate all their combinations, and

impossible therefore to give a list of species. Accordingly

M. Necker[76\8] gives seventy-one Species of _spath

calcaire_, and then says, 'Nous n'avons pas énumeré la

dixième partie des espèces connues de ce genre, qui se

montent à plus de huit cents.' Again, in many substances, of

which few crystals are found, every new specimen would be a

new species; if indeed it were perfect enough to be referred

to a species at all. But from a specimen without perfect

external form, however perfect in crystalline character,

although everything else might be known,--angles, optical

properties, physical properties, and chemical

constitution,--the species could not be determined. Thus M.

Necker says[77\8] of the micas, 'Quant aux espèces propre à

chaque genre, la lacune sera presque complète; car jusqu'ici

les cristaux entiers de Mica et de Talc n'ont pas été fort communs.'

[Note 76\8: _Règne Mineral_, p. 364.]

[Note 77\8: _Ib._ ii. 414.]

These inconveniences arise from neglecting the leading rule

of natural history, that the _predominant principle_ of the

existence of an object must determine the Species; whether

this principle be Reproduction operating for Development, or

Crystallization operating for Permanence of form. We may add

to the above statement of inconveniences this;--that if M.

Necker's view of mineralogical species be adopted, the

distinction of Species is vague and indefinite, while that

of Genera is perfectly precise and rigorous;--an aspect of

the system entirely at variance with other parts of Natural

History; for in all these the Species is a more definite

group than the Genus.