subsist between them. Having made so many allusions to this principle of classification, we shall give a short sketch of its general outline, from Mr. Jamieson's Treatise on the "External Characters of Minerals." As these characters bear a reference to the senses, seeing, hearing, smelling, tasting and feeling, they may be considered under the heads of colour, sound, smell, flavour, hardness and weight. With regard to the first, it be came a principal object with Werner to distinguish, and note every particular tint which bodies reflect, and to illustrate them by a comparison with the most familiar objects. In pursuance of this plan he sets out by establishing a certain number of standard colours to which all the others might be referred; and the following list of them exhibits the division which he thought proper to adopt, and also the substances in which the characteristic shades of these standard colours are most readily to be found.

"White, as in new-fallen snow.

Grey, as in well-burnt wood ashes.
Black, as in velvet.

Blue, as in Prussian, or Berlin, blue.
Green, as in the emerald.

Yellow, as in temons.

Red, as in carmine.

Brown, as in a ripe chesnut."

These colours are so arranged that there is a natural and imperceptible transition from one into the other; and even in the same suite of any particular colour there is a gradation in point of intensity, from the first member of it through all the succeeding, until it reaches its maximum in the characteristic substance, from which it again recedes, diminishing in strength, and finally passes into the suite which follows next in order. We shall give an example whereby these remarks will be rendered more intelligible, abridged as in the former case from the work on external character. The green suite проп which we fix, is connected with the blue going before, and with the yellow coming after it. The examples which are subjoined are well selected, and illustrate clearly the various gradations of tint, from the ter mination of the one suite to the commencement of the other.

GREEN.

"The chief or principal colour is emerald green. a. Verdigris green is composed of emerald green, with much Berlin blue, and a little white. It is the link which connects the green and the blue colours together. Examples, copper green and Siberian felspar.

b. Seladon green is composed of verdigris green and ash grey. Examples, green earth, Siberian and Brazelian beryl.

c. Mountain

c. Mountain green is composed of emerald green, with much blue, and a little yellowish grey, or verdigris green, with yellowish grey. It passes into greenish grey. Examples, beryl and hornstone.

d. Leek green is composed of emerald green, with a little brown, and somewhat more blueish grey. Examples, nephrite, com

mon actynelite and prase. e. Emerald green. The principal or pure unmixed green. All the preceding green colours are more or less mixed with blue, and at length pass into it; but the following part of the green series, by the increasing proportion of yellow, at length passes into yellow. Examples, emerald and fibrous malachite. f. Apple green is emerald green, mixed with a little greyish white. It passes into greenish white. Examples, copper, nickel, ochre, and crysaprase.

g. Grass green is emerald green, mixed with a little lemon yellow. The colour of fresh newly-spring grass. Example, uranite. h. Blackish green is grass green, mixed with a considerable portion of black. It passes into greenish black. Example, precious serpentine.

i. Pistachio green is emerald green, mixed with a little yellow, and a small portion of brown. Example, crysolite.

k. Asparagus green is pistachio green, mixed with a little greyish

white, or emerald green mixed with yellow and a little brown. It passes into liver brown. Examples, garnet and oliven ore. 1. Olive green is grass green, mixed with much brown, or emerald green, mixed with a little yellow, and much brown. It passes into liver brown. Examples, garnet and oliven ore.

m. Oil green is emerald green, mixed with yellow, brown and grey, or pistachio green, with much yellow, and light ash grey. Examples, fullers earth and beryl.

n. Siskin green is emerald green, mixed with much lemon yellow, and a little white. It makes the transition to the yellow colour. Examples, uran mica, and stealite."

Thus have we passed by a very natural transition from the last member of the blue suite, through the green into the yellow; which latter, again, after having passed through a regular series to the lemon, or characteristic, shade, connects itself with the red suite by means of the orange yellow. In this way a practised eye will perceive at once to which description of colour any particular specimen belongs, whilst he is by the same means supplied with a copious notation or nomenclature, to express the numerous varieties into which every principal colour is divided.

In the wide field of nature, however, there is not only an im mense variety of tints and shades, but there are also many different degrees of strength or intensity in the same radical colour. Thus the violet blue may be pale, light, deep, or dark. Colours are also modified by the tollowing circumstances, which exhibit their effects in a variety of ways.

2

"Tarnish

"Tarnish of Colour,

Play of Colour,

Changeability of Colour,
Iridiscense of Colour,
Opalascense of Colour,

Permanent Alteration of Colour,

Delineations (natural) formed by Colour."

These properties are illustrated at considerable length in the former of the two works now before us, to which we willingly refer the mineralogical student. Leaving colour, the author proceeds to detail the characters connected with the external aspect of minerals in regard to shape, surface, and lustre. Shape is divided into four heads:

"Common external Shape,
Particular external Shape,
Regular external Shape,

Extraneous external Shape."

As all of these classes have their subordinate differences, which are very minutely described, we shall hold it sufficient to give a specimen of the author's manner under one of the divisions. We select the second Particular external Shape, which presents itself to the reader in five separate heads; namely, Longish particular external Shape, Roundish particular external Shape, Flat particular external Shape, Cavernous particular external Shape, and Entangled particular external Shape. The first of these, the Longish particular external Shape, has the following varieties which we set down without their accompanying illustrations.

a. Dentiform, as in silver glauce.
b. Filiform, as in native silver.

c. Capillary, as in several metals.

d. Reticulated, as in the native silver of Gotthelf.

e. Dendritic, as in native silver of Mexico.

f. Coralloidel, as in a species of calc sinter.

g. Stalactitic, as in common calc sinter.

h. Cylindrical, as in lead glauce and brown iron-stone.
i. Subiform, as in calc sinter.

k. Claviform, as in brown and black haematite.

1. Fructicose, as in calc sinter and black haematite."

We must not proceed farther. The novice in minerals, however, may rest assured that the whole doctrine of shape is given at great length, and with much perspicuity, not one word of which is superfluous to him who wishes to be thoroughly instructed. On the subject of fundamental figure there is not less Nu

VOL. VI. NOVEMBER, 1816.

detail,

detail, the author very properly extending his observations to the following particulars:

"1st, Parts of the fundamental figure.

2d, The varieties or kinds of the fundamental figure.

3d, The differences of each fundamental figure in particular.
4th, The alterations of the fundamental figure.

5th, The division of the planes of fundamental figure.
6th, Multiplied alterations of fundamental figure."

These characters are of great importance in discriminating mineral bodies; and, in many instances, the family, the species, or sub-species, to which a particular substance belongs, is immediately determined by the figure which it has assumed. The fracture of a mineral is likewise, in many cases, characteristic of its species. It is hardly necessary to state, that by the fracture of a stony body is meant, that rent or plane which is produced through the solid of a mineral (not in the direction of accidental rents, or the natural operations of the distinct concretions) when it is forcibly struck with a hammer. The piece struck off will present, on its newly-exposed surface, either an even or an uneven fracture, or it may be conchoidal, splintery, earthy, or huckly; or lastly, according to a more general description, the fracture may be compact, fibrous, radiated, or foliated. As to the shape of the fragments themselves, they may be,

"1st, Cubic, as in lead glauce and common salt.
2d, Rhomboidal, as in brown spar and felspar.
3d, Trapezoidal, as in foliated coal.

4th, Pyramidal, as in fluor spar.

5th, Dodecahedral, as in blende."

With regard to transparency there are the following degrees. A mineral is either simply transparent, the body seen through it appearing single; or it is duplicating, the body seen through appearing double. The first is exemplified in selenite, the second in calc spar. Again, a mineral is semi-transparent when it shews an object indistinctly, as chalcedony and precious opal; translucent when, as in the case of pitchstone and quartz, the rays of light enter and faintly illuminate it; translucent on the edges, when the light penetrates only the thin parts and corners, as in hornstone and heliotrope; or finally, it is opaque when, as is exemplified in chalk, no light whatever can make its way through it.

To finish our abstract on the characters which respect the sense of sight, we have only to mention streak and soiling. When some minerals are scratched with the point of a knife,

the

the colour of the parts affected is greatly heightened, whilst in others, that colour is completely different from the rest of the mass. Cinnabar, for example, has a crimson-red colour, but yields a scarlet-red streak; red orpiment is aurora-red, but yields an orange-yellow streak; iron glauce has a steel-grey colour, but gives a cherry-red streak. Native gold and silver, again, retains when scratched their natural colour, but have its lustre considerably heightened.

Soiling describes the mark or stain which is left by a mineral when it is impugned upon another, or squeezed between the fingers. Chalk and mountain-soap soil strongly; molybdæna, lead glauce, and graphite, are said to soil slightly, thus affording a kind of standard to which other soft bodies may be coinpared.

The characters which address themselves to the other senses, hardness, tenacity, frangibility, flexibility, and adhesion to the tongue; as relating to touch, a ringing sound, a grating sound, and a creaking sound; as relating to the ear, to which we may add, without specifying the organs, coldness, weight, smell, and

taste.

From the mere outline which we have given, it must be very obvious, that the oryctognostic system, unfolded in Mr. Jameson's two books, must be the fruit of immense labour and diligent study. There, are no doubt, many things in it capable of great improvenient, and among these we should mention the terms which are employed to denote the different degrees of any quality, such as hardness and weight, as characteristic of a mineral substance. The nomenclature in this department is not only awkward, but it is also defective in point of precision; and we are moreover of opinion, that other writers, not once to be compared to our author in respect of knowledge, have succeeded better than he in the simplicity and clearness of their notation. The wonder is, however, not that there remains any thing to be done, but that there has been so much achieved. The fabric is raised, lofty and magnificent; and we remark upon it, not that the foundation is bad, nor the plan injudicious, but merely that the pillars are not sufficiently polished, and the decorations not quite finished.

Having entered at much length into the "Treatise on external Characters," we will not say all that we intended on the "System of Mineralogy:" indeed, as we have already observed, it partakes very much of the nature of a dictionary, and scarcely admits of critical remark farther than concerns the mere arrangement or division. Minerals have usually been classed under four heads, the Earthy, the Saline, the Inflammable, and the Metallic, and Mr. Jameson follows this order, and adopts these