screens of intervening trees or clumps of buildings; such perforations assisting by their framework the distant tone of color with which the most remote objects are nevertheless sufficiently embodied out. Now, though the interposition of the atmosphere gives us the means of producing the effect of distance in a picture, yet the mind requires a certain variety to hold it in amusement, and a certain appearance of substance to give a reality to the scene. On the other hand, when the atmosphere is deprived of the means of refraction, by reason of its clearness, a false representation is produced, and objects appear nearer than they are in point of truth (as may be perceived in many scenes in Switzerland), and the eye is deprived of the gratification of viewing the outlines of objects through a variety of strengths.12 When we reflect that the art of painting is an attempt to deceive the eye, in representing upon a perpendicular surface the variety of planes upon which the several objects in Nature are placed; when we reflect that the painter is deprived of many collateral means of assisting the deception, it requires his whole knowledge to be employed in working out the result, lines possessing distinctness of form, bulk and minutiæ, light and dark to give them their full force upon the eye, colors unassociated with atmospheric influence, with the reverses of all these assisting by contrast. We must admit that a knowledge of aërial perspective embraces in its effects nearly the whole art of portraying the retiring and advancing of objects. In the works of Albert Cuyp and Claude Lorraine we have many examples of this quality in perfection, where the interposition of the air, whether of a yellow or blue color, imbues every object with its just proportion according to its relative distance from the foreground, and the near objects are strengthened by black or red or other colors less in unison with the general tone of the picture; also in the foreground of many of the works of Cuyp and others, the student may perceive the shadows under the leaves and stones in the foreground, broad, black and of large, decided forms. Now, though this is the general characteristic of this department, we see in many works of the best artists objects very much diminished in size according to their true perspective distance, yet possessing a force of color little removed from the tints of the objects in the foreground. Neither does such harshness prevent them keeping their situations. This arises from the very small space they occupy upon the retina, forming so diminished a picture in the eye, even when painted of the size of Nature. 13 In historical compositions the most distant

12 De la Hire enumerates five circumstances which assist us in judging of the distance of objects, namely, their apparent magnitude, the strength of the coloring, the direction of the two eyes, the parallax of the objects, and the distinctness of their small parts. Painters, he says, can take advantage only of the two first mentioned circumstances, and therefore pictures can never perfectly deceive the eye; but in the decorations of theaters, they in some measure make use of them all, different planes being made use of, and different degrees of distinctness.-Accidens de la Vue, p. 358.

13 Speaking of the retina, Dr. Roget says, "Few spectacles are more calculated to raise our admiration than this delicate picture, which Nature has with such exquisite art, and with the finest touches of her pencil, spread over the smooth canvas of this subtle

objects form often a portion of the story. They are, therefore, to be pronounced with that strength which will enable them to assist the painter in producing the desired effect on the mind of the spectator, nor does truth appear at all violated, provided they are not made out with too great precision. In history and the higher walks of the art, where the greatest liberties are allowed, it may be less necessary to notice the conduct of the best artists in this particular; but we often find it even in landscapes and common representations of natural effects. How often have we observed wood scenes and others prevented from being heavy by the introduction of a few dark touches, and breadth of color and space produced by the small dark of a figure. When, however, the effect of hazy sunshine (such as we see in the works of Cuyp) is to be represented, the most distant objects ought to be rendered with the greatest delicacy; for, the whole atmosphere being then filled with the refraction of light, the middle-ground objects appear to be made out with a uniform tone or half-tint. Aërial perspective, therefore, though understood to be subject to rule, is more completely under the control of the painter than lineal perspective.

I have noticed elsewhere1 how much in reality objects in motion attract the eye of the spectator, with what intelligence the peculiar walk of those we know is communicated even at great distances. This is one reason out of many why we are allowed to pronounce parts of a picture with more strength than other parts, as the mind of the spectator must be arrested with the same force it feels itself acted upon under natural effects.

The application of aërial perspective, therefore, enables the artist to keep the several objects in their respective situations, and give a natural reality to the most complicated scene. A row of columns will diminish according as they are drawn true to lineal perspective, but it is to this

nerve; a picture which, though scarcely occupying a space of half an inch in diameter, contains the delineation of a boundless scene of earth and sky, full of all kinds of objects, some at rest and others in motion, yet all accurately represented as to their forms, colors and positions, and followed in all their changes without the least interference, irregularity or confusion. Every one of those countless and stupendous orbs of fire, whose light, after traversing immeasurable regions of space, at length reaches our eye, is collected on its narrow curtain into a luminous focus of inconceivable minuteness, and yet this almost infinitesimal point shall be sufficient to convey to the mind, through the medium of the optic nerve and brain, a knowledge of the existence and position of the far distant luminary from which that light has emanated.-Doctor Roget's Bridgewater Treatise.

14 In Practical Hints upon Light and Shade.

quality of light and shade that they are indebted for their effect upon the eye. Also, two angles may occupy the same space on the retina, but by this power one is made to approach, and the other to recede, so that one is diminished to the size of a tent, the other increased to a pyramid.

In Plate I, Fig. 1, the Canal of Dort, by Cuyp, in the Bridgewater collection, we not only find an excellent example of aërial perspective, but also of that assemblage of lines produced by the repetition of forms, which assists the receding of objects from their diminution, the doubling of the lines in producing richness of effect, and that harmony which arises from one line counteracting another in its direction, giving thereby a general balance to the whole. The effect of aërial perspective upon the eye being mainly attributable to the application of shadow to the several outlines, thereby giving them their approaching or receding character, such arrangement is to be chosen which will give them this quality, and which is to be afterward repeated in smaller portions through the piece. In accidental combinations in Nature we often perceive this arrangement (as in Fig. 2, Plate I), which ought to be sketched and reflected upon as one of the great means we have of enabling us to cope with her under the disadvantage of working upon a flat surface. We also find aërial perspective indebted in its effect to the collection of many parts, whose shadows form a mass of half-tint, their distance bringing them in apparent contact, owing to their diminution; while their softness gives them apparent distance, owing to their want of minute parts, as in Fig. 3, Plate I.

To go through on every occasion with a variety of examples would, I feel persuaded, only perplex the student. If he comprehends. any rule, it is easy to extend it. To those who understand slowly, reflection on one or two diagrams will be of more service than educating the eye without impressing the mind. The real trouble in life, in all professions, is the trouble of thinking, to escape which the most laborious trifling is caught at; but, if fairly grappled with at the outset, everything becomes clear, and, in after-life, that which is a continual annoyance to many becomes one of the greatest gratifications. Why is it that, to the eye of an artist, the drawing of a complicated plan is rendered clear at a glance, while to others it requires a multitude of figures of reference and a long explanation?