of short or long continuance has generally the immediate effect thereon of fire more or less intense, according to the laws of combustion and chemical agency. It is, indeed, some sort of criterion of the durability and changes of colour in pigments, that time and fire produce similar effects thereon: thus if fire deepen any colour, so will time; if it cool or warm it, so will time; if it vary it to other hues, so will time; and if it consume or destroy a colour altogether, so also will time ultimately; but the power of time varies extremely with regard to the period in which it produces those effects which are instantly accomplished by fire: fire is also a violent test, and subject to many exceptions.

That there is no absolute but only relative durability of colour may be proved from the most celebrated pigments;-thus the colour of ultramarine, which, under the ordinary circumstances of a picture, will endure a hundred centuries, and pass through naked fire uninjured, is presently destroyed by the juice of a lemon or other acid. So again the carmine of cochineal, which is very fugitive and changeable, will, when secluded from light, air, and oxygen, continue half a century or more; while the fire or time which deepens the first colour will dissipate the latter altogether. Again, there have been works of art in which the white of lead has retained its freshness for ages in a pure atmosphere, and yet it has then been changed to blackness after a few days', or even

hours' exposure to a foul air. These and other affections of colours will be instanced throughout when we come to the consideration of individual pigments; not for the purpose of destroying the artist's confidence in his materials, but as a caution and guide to the availing himself of their powers properly.

It is therefore the lasting under the ordinary conditions of painting, and the common circumstances to which works of art are exposed, which entitle a colour or pigment to the character of permanence; and it is the not-so-enduring which subjects it properly to the opposite character of fugacity; while it may obtain a false repute for either, by accidental preservation or destruction under unusually favourable or fatal circumstances, all of which has been frequently witnessed.

It has been supposed by some that colours vitrified by intense heat are durable when levigated for painting in oil or water. Had this been true, the artist need not have looked farther for the furnishing of his palette than to a supply of wellburnt and levigated enamel colours; but though these colours for the most part stand well when fluxed on glass, or in the glazing of enamel, porcelain, and pottery, they are almost without exception subject to the most serious changes when ground to the degree of fineness necessary to render them applicable to oil or water painting, and become liable to all the chemical changes and

affinities of the substances which compose them. These remarks apply also to those who ascribe permanence to native pigments only, such as the coloured earths and metallic ores.

Others, with some reason, have imagined that when pigments are locked up in varnishes and oils, they are safe from all possibility of change; and there would be much more truth in this position if we had an impenetrable varnish,—and even then it would not hold with respect to the action of light, however well it might exclude the influences of air and moisture: but, in truth, varnishes and oils themselves yield to changes of temperature, to the action of a humid atmosphere, and to other chemical influences: their protection of colour from change is therefore far from perfect; and the above opinion of them is only in some degree true, but ought not to render the artist inattentive to the durability of his colours in themselves. Reynolds, unfortunately, entertained this opinion of the preserving power of varnishes; and, although the practice of his own palette was exceedingly empirical, he was an utter condemner of such practice in others.⁕

On the other hand, want of attention to the unceasing mutability of all chemical substances, and their reciprocal actions, has occasioned those changes of colour to be ascribed to fugitiveness of

* Northcote's "Memoirs of Sir J. R." Supplement,

p. 80.

the pigment, which belong to the affinities of other substances with which they have been improperly mixed and applied. It is thus that the best pigments have sometimes suffered in reputation under the injudicious processes of the painter, and that these effects and results have not been uniform in consequence of a desultory practice. If a pigment be not extremely permanent, diluting it will render it in some measure more weak and fugitive; and this occurs in several ways,— by a too free use of the vehicle, by complex mixture in the formation of tints, and by distribution, in glazing or lackering, of colours upon the lights downward, or scumbling colours upon the shades upward; or, according to a mixed mode, in which transparent and opaque pigments are combined, as umbre and lake—much employed by the Venetian painters.

The fugitive colours do less injury in the shadows than in the lights of a picture, because they are employed purer and in greater body in the shadows, and are, therefore, less liable to decay by the action of light and by mixture; and, by partially fading, they balance any tendency to darken, to which the dead colouring of earthy and metallic pigments is disposed.

The foregoing circumstances, added to the variableness of pigments by nature, preparation, and sophistication, have often rendered their effects equivocal, and their powers questionable; all which considerations enforce the expediency of using

colours as pure and free from unnecessary mixture as possible; for simplicity of composition and management is equally a maxim of good mechanism, good chemistry, and good colouring. Accordingly, in the latter respect, Sir Joshua Reynolds gives it as a maxim, that the less pigments are mixed, the brighter they appear; the causes of which we have mentioned already. His words are: His words are: "Two colours mixed together will not preserve the brightness of either of them single, nor will three be as bright as two of this observation, simple as it is, an artist who wishes to colour bright will know the value."—Note xxxvii. to Dufresnoy's "Art of Painting."

There prevail, notwithstanding, two principles of practice on the palette, opposed to each otherthe one, simple; the other, multiple. That of simplicity consists in employing as few pigments, &c. as possible; according to the extreme of which principle the three primary colours are sufficient for every purpose of the art. of the art. This is the principle of composition in colouring, the opposite of which may be called the principle of aggregation, and is in its extreme that of having as many pigments, if possible, as there are hues and shades of colour.

On the first plan every tint requires to be compounded; on the latter, one pigment supplies the place of several, which would be requisite in the first case to compose a tint; and as the more pigments and colours are compounded, the more they