The foregoing circumstances, added to the variableness of pigments by nature, preparation, and sophistication, have often rendered their effects equivocal, and their powers questionable. These 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 respect to the latter, Sir Joshua Reynolds remarks, "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." There prevail, notwithstanding, two principles of practice on the palette, opposed to each other--the one, simple; the other, multiple. The first is that of having as few pigments as possible; and consists, when carried to the extreme, in employing the three primary colours only. The second is that of having a number of pigments; and consists, also when carried to the extreme, of employing as many, if possible, as there are hues and shades of colour. On the former plan, every tint requires to be compounded; on the latter, one pigment supplies the place of two or more. Now, the more pigments are mixed, the more they are deteriorated in colour, attenuated, and chemically set at variance. Original pigments, that is, such as are not made up of two or more colours, are purer in hue and generally more durable than those compounded. Hence pure intermediate tints in single, permanent, original pigments, are to be preferred to pigments compounded, often to the dilution and injury of their colours. Cadmium Orange, for instance, which is _naturally_ an orange pigment and not composed of red and yellow, is superior to many mixtures of those colours in a chemical sense, and to all such mixtures in an artistic sense. At the same time, it is quite possible for the artist to multiply his pigments unnecessarily. Colours are sometimes brought out under new names which have no claim to be regarded as new colours, being, indeed, mere mixtures. Compound pigments like these may most frequently be dispensed with, in favour of hues and tints composed extemporaneously of original colours upon the palette. It may be inferred from the foregoing that, between the modes of employing as few pigments as possible, and of having as many as there are hues and shades of colour, a middle course is the best. But, whatever the practice adopted, permanent _original_ pigments should be used as often as the case will admit; it being borne in mind, that a pigment may be compound, although its colour may be primary. As a rule, the less colours are mixed, the purer, brighter, and more lasting they will be found.