equal to that at which the rays of the sun descend upon the body, at that point, which is the seat of what we term the high light, there is reflected a certain quantity of the perfect light of the sun, or white; which destroys the colour in proportion to its own degree of intensity, by rendering it whiter than the general actual hue surrounding this bright light. This is rendered intelligible by referring to halfpolished substances, as silk, or satin, but it takes place more or less in all.

But for the present, I wish you to dismiss this consideration from your minds, and revert to the first proposition; viz. that coloured substances obtain their hues from light, and lose them when deprived of it. Connect this proposition with another, viz. that shade, abstractedly considered, is always alike in tone; and you will then perceive, that the same tone of darkness, whatever be its degree, pervades all colours as they recede from light, to their complete union and total loss in shadow.

We may arrive at the same conclusion by a more technical mode of proceeding; and, for the purpose of explaining it, I lay before you the ingenious diagram given in a work published many years ago, by Moses Harris, under the title of "The Natural System of Colours." In the circular portion of his diagram, the pris

matic colours, red, blue, and yellow, are united, consonant with the system of the rainbow, by orange, green, and purple; and all are graduated from the centre outwards, that is, from their utmost intensity, to the faintest tint approaching to white; and those tints are marked by a scale of strength, say twenty-five; supposing the five marked circular spaces to contain five degrees each.

tive colours (as he well terms them), red, blue, and yellow, in the pigments we employ, is productive of black; or a hue in which there is a total privation of all colour, and which therefore assumes the perfect character of shade.*

Now, if the union of the three primitive colours in their utmost degree of intensity be productive of perfect shade; it must be apparent, that their union in fainter but equal degrees of tint must be productive of the same negative colour, or tone; in a degree consonant to that of the tints of the colours employed: proving that which I before stated; viz. that all shade, in every degree, is alike in tone; and will produce the like effect on every coloured object subjected to it.

These two points then, truth of imitation of an actual colour, and unity of shade, I conceive to be the firm, though simple basis of true colouring in its primitive purity and simplicity; that is, when considered without regard to reflections. And yet operating even then, when reflections are admitted; for reflection, being light transmitted through another medium, but produces another colour upon the surface of the body where it reaches; and its gradations to the

In curious contradistinction to the effect of aerial prismatic colours, the production of their union being white light! Nevertheless, in one point they agree, viz. that each is a negation of colour.

shadowed parts where it cannot reach, are subject to the same law.

Thus much for the consideration of any single colour, and its varieties, in union with shade. Our next object is, the union of the different colours with each other. It appears from numberless observations, that the human eye is so constituted with regard to colour, that though it derives pleasure from viewing each of the three primary colours alone, yet, if two of them are introduced to its view together, it then requires for its entire gratification the presence of the third also; and that want causes a physical sensation in the eye itself, which without mental agency, and in a manner unknown to us, produces the third.

For, let those two colours be united, and the compound colour formed by their union be exposed to the eye for a time, and then suddenly removed from before it; the form of the figure in which the compound colour was exhibited, will remain present to the view, but tinged of the colour omitted. That is, if the compound be purple, the spectrum will be yellow; if orange, blue; and if green, red; and even while the original colours are singly before the eyes, if regarded very attentively, each of them will be seen surrounded by the compound of the other two.

This points out, I conceive, the physical source of that pleasure which we derive from well-arranged colouring, and of those sensations, of gratification or of dissatisfaction, which must have been frequently experienced by every painter as he produced, or neglected, the requisite unions of colours. But whether I have assigned the real cause of it, or no, the fact is certain, that there are sensations of pleasure and of displeasure arising to our sense of vision, accordingly as colours are arranged or assorted.

We universally acknowledge great delight in regarding the rainbow in the order or succession of its colours, as well as in their delicate and even imperceptible degrees of union; and no one has yet discovered an arrangement of them, more gratifying to our eyes, or to our understanding.

When the three primary colours are placed before us, our eyes accept the vision with a certain degree of pleasure: but they are most grati fied when the intermediate colours are properly introduced, and the whole scale of the colours which constitute a ray of light is presented to them.

This arrangement, then, seems the most proper for adoption by the painter, as producing the most pleasing concord of colours; and we