even in enamel; but the great price prevents the general use of it.

Ultramarine ashes. This is the residuum after washing the lapis lazuli, in which a portion of the ultramarine still remains. It is very subject to be adulterated. It is not so bright as ultramarine, being, like that colour, with a tint of red and white in it. When genuine it stands well.

Prussian blue. This colour is iron combined with the prussic acid. It is made in the following

manner.

Two parts of purified potash are most intimately blended with three parts of dried and finely pulverized bullock's blood. The mass is first calcined in a covered crucible, and on a moderate fire, until no more smoke or flame appear; and it is after this brought to a complete, yet moderate, ignition. Or equal parts of potash and finely-powdered coals, prepared from bones, horns, claws, &c. are mingled, and heated in a covered crucible to a moderate redness. This done, either of these two calcined masses is, after cooling, lixiviated with boiling water, and the lixivium filtered. Nothing remains now but to make a solution of one part of green vitriol and two parts of alum, and to add to it while yet hot the above lixivium, little by little however, and to separate the greenish-blue precipitate, which then forms by means of a filtre. If afterwards a slight quantity of diluted muriatic acid be affused upon this precipitate, it assumes a beautiful dark-blue colour. The operation is terminated by edulcorating and drying the pigment thus prepared. Prussian-blue is an extremely beautiful colour when properly prepared, and stands well. Common Prussian-blue is apt to contain some iron, which causes it to turn greenish or olive.

Verditer is a blue pigment, obtained by adding chalk or whitening to the solution of copper in aqua fortis. The best sort is prepared by the refiners, who employ for this purpose the solution of copper, which they obtain in the process of parting, by precipitating silver from aqua fortis by plates of copper. Common verditer is made from the sulphate of copper, or blue, by the manufacturers in Sheffield and Birmingham. Verditer is only used for very coarse purposes, chiefly by the paper-stainers. It has been sometimes called SANDERS blue, from ignorance of the meaning of the term cendres blues, or blue ashes, which the French call it.

Indigo. This colour is extracted from a plant called Anil, that grows in the East and West Indies. It is not so bright as Prussian-blue, but it is cooler, and has the advantage of being very durable. When dissolved by the sulphuric acid, it forms ScoTT's liquid blue, so much used for colouring silk stockings, &c.

Smalt. This is glass coloured with cobalt, and ground to a fine powder. Its coarseness prevents its being used much for painting in oil or water. It is employed sometimes by sterwing it upon a ground of oil-paint. It is also used in enamel

painting. It stands well.

Blue Bice. This is only smalt more finely levigated.

Yellow Colours.

Indian yellow. This is the brightest of all yellows for water-colours, and is perfectly durable. It is said to be procured from the urine of the

buffalo. In the East Indies it is a very common and cheap colour; the natives there use it commonly for colouring their calicoes, which they do without any mordant, so that the colour is washed out again when the cloth is dirty.

King's yellow. This colour is orpiment refined, which is a substance dug out of the earth, and consists of sulphur joined to arsenic; or it may be prepared by subliming sulphur with arsenic. It is of a very bright yellow, but does not stand very well; and great caution should be used in employing it, as it is a strong poison.

Naples yellow. This is a very durable and bright pale yellow; it comes from Naples, and is supposed to be prepared from lead and antimony.

Yellow ochre. This is an earth coloured by oxyd of iron. It is a cheap colour, and not very bright; but is valuable on account of its standing well.

Roman ochre. This is a superior kind of yellow ochre.

Dutch pink. This pigment is formed of chalk coloured with the juice of French berries, or other vegetables affording a yellow colour. It does not stand, and is chiefly used for common purposes.

Gamboge is a gum brought from the East Indies. It readily dissolves in water, and is a fine bright yellow. It is used only in water, and is very

serviceable.

Massicot is an oxyd of lead, prepared by calcining white-lead. It is very little used, the colour not being very bright.

Gall stones. This is a concretion or hard substance, formed in the gall-bladders of beasts; or it

may be obtained from the gall of animals. a very rich colour, but does not stand.

It is

Raw Terra Sienna, is a native ochrous earth brought from Italy. It is a fine warm colour, and stands well.

French berries. A liquor may be extracted from these, which is useful as a stain for some coarse purposes; but it does not keep its colour. Turmeric root, and saffron, may be used for similar purposes.

Orange lake is the tinging part of annatto precipated together with the earth of alum. not stand.

It does

Brown pink is the tinging part of some vegetable substance precipitated upon the earth of alum. It is of a fine rich greenish yellow, but does not stand in water.

Green Colours.

There are few colours that are useful as greens ; accordingly, it is the practice with artists, to form their greens by the mixture of blue and yellow colours. By varying these, a vast variety of green tints may be obtained.

Sap green. This colour is the concreted juice. of the buckthorn-berries. It is never used in oil. It is employed chiefly in flower-painting and colouring prints, &c.

Verdigris. If plates of copper, moistened from time to time with vinegar, be left exposed to the air, they will be converted into a green oxyd, called verdigris: this is an imperfect oxyd of copper, combined with a small portion of acetic acid, carbonic acid, and water. It is prepared in

large quantities, chiefly in France near Montpellier, by stratifying copper-plates with the husks of grapes yet under vinous fermentation, which soon grow acid, and corrode the copper. After the plates have stood in this situation for a sufficient time, they are moistened with water, and exposed in heaps to the air. The verdigris is scraped off from their surface as it forms.

Verdigris is of a bluish-green colour, but has no body, and does not stand. It is only used for very coarse purposes. It answers best when used in varnishes.

Distilled verdigris, sometimes called crystals of verdigris, is prepared from common verdigris, by dissolving it in vinegar. It is of a very bright green, and is used chiefly for varnishes, and in colouring maps, &c.

Brown Colours.

Bistre is the finer part extracted from the soot of burnt wood. It is much used for sketches in water-colours, being a transparent warm colour.

Cologne earth. This is a mineral substance of a dark blackish brown colour. It is a very useful colour; though what is generally sold in the shops for Cologne earth is an artificial mixture of several colours.

Raw umbre is a native ochreous earth, of a light brown. It stands well.

Burnt umbre. This is only the last mentioned colour, calcined in the fire. It then acquires a rich deep brown, and is of great use, being a fine colour, and standing perfectly well.

Asphaltum. This colour is used in oil, and is of a very rich deep brown. It is a transparent or glazing colour. It will not work in water, but