[15] Note, though I have advised the observing objects by a front light, for the sake of the better distinguishing our four fundamental species of shades, yet objects in general are more advantagiously, and agreeably seen by light coming side-ways upon them, and therefore generally chose in paintings; as it gives an additional reflected softness, not unlike the gentle tone of an echo in music. [16] As an instance that convex and concave would appear the same, if the former were to have no reflection thrown upon, observe the ovolo and cavetto, or channel, in a cornice, placed near together, and seen by a front light, when they will each of them, by turns, appear either concave, or convex, as fancy shall direct. I have now only to add, that as before observed, Chapter IV, page 23, that the oval hath a noble simplicity in it, more equal to its variety than any other object in nature; and of which the general form of a face is composed; therefore, from what has been now shewn, the general gradation-shade belonging to it, must consequently be adequate thereto, and which evidently gives a delicate softness to the whole composition of a face; insomuch that every little dent, crack, or scratch, the form receives, its shadows also suffer with it, and help to shew the blemish. Even the least roughness interrupts and damages that soft gradating play of shades which fall upon it. Mr. Dryden, describing the light and shades of a face, in his epistle to Sir Godfrey Kneller the portrait painter, seems, by the penetration of his incomparable genius, to have understood that language in the works of nature, which the latter, by means of an exact eye and a strict obeying hand, could only faithfully transcribe; when he says, Where light to shades descending, plays, not strives, Dies by degrees, and by degrees revives. CHAPTER XIII. _Of COMPOSITION with regard to LIGHT, SHADE and COLOURS_. Under this head I shall attempt shewing what it is that gives the appearance of that hollow or vacant space in which all things move so freely; and in what manner light, shade and colours, mark or point out the distances of one object from another, and occasion an agreeable play upon the eye, called by the painters a fine keeping, and pleasing composition of light and shade. Herein my design is to consider this matter as a performance of nature _without_, or before the eye; I mean, as if the objects with their shades, &c. were in fact circumstanced as they appear, and as the unskill'd in optics take them to be. And let it be remarked throughout this chapter, that the pleasure arising from composition, as in a fine landskip, &c. is chiefly owing to the dispositions and assemblages of light and shades, which are so order'd by the principles called OPPOSITION, BREADTH and SIMPLICITY, as to produce a just and distinct perception of the objects before us.