At the present time, so far as my observation goes, linear perspective on the grand scale is not so much sought after as it was in the early part of this century. That is to say, the Claude-Poussin-Turner ten-mile stretches of landscape, with streams and groves and background mountains have disappeared in favor of the meadow strip, a marsh land in fog, a side-hill, or a bit of wood interior. The modern painters who are, above all, the great landscapists, seem to think that these long distances, with mountain – peaks and rolling clouds, involve too much form at the expense of the painter’s feeling and sentiment. I cannot give the exact why of this, but I offer you as a suggestion that modern painting would appear to be nearer of kin to music than to sculpture or architecture, and is continually striving to blend form with sympathetic execution, and thus make one harmonious whole which shall emphasize neither nature nor man, yet embody both. Where form is so predominant as in mountain pieces, the state of feeling or emotion in the man and the execution, are overbalanced and comparatively lost. This, I take it, may partly account for the fact that no painting of the Alps, nor of the Rocky Mountains, nor of deep valleys or gorges, has ever been considered satisfactory art. It may also suggest the reason why the landscape painter of modern times, as Corot, chooses the low-lying scene with few trees or hills ; as Troyon or Daubigny the marsh, the meadow, or the sedgy river; as Diaz or Rousseau the quiet wood-interior; leaving the frowning precipice, the lurid sky, the blue valley far beyond, to those who have neither power of sentiment nor skill of execution, and must attract by the proportions of their canvas or their subject. The recent use to which atmosphere and its effects have been put has also been the cause to some extent of the abandonment of great distances in landscape, the air being used as a screen to shut out the background. Claude and Poussin did not perhaps value aerial perspective highly enough. They seemed to place their reliance more on the shrinkage of line than. the fading of color. The moderns in some cases have gone a little to the other extreme, suffocating the landscape at times with something intended for air, but which looks like smoke, or fog, or a scumble of gray paint. In pictures other than landscapes or marines, the importance of linear perspective has not perceptibly diminished. It is quite as necessary to-day to give correctly the dimensions of a room, the top of a table, or the legs of a chair, as it used to be in classic times ; and while linear perspective is not so much relied upon for effect in certain pictures as it once was, yet its value is not to be lightly considered nor its beauty overlooked in any picture.
Aerial Perspective.The second part of this subject deals with aerial perspective, which may be considered in effect as the atmospheric dissipation and final obliteration of lines, colors, lights, and shades as the objects which show them recede in the distance. Heretofore we have been speaking of the diminution of form as the distance increases; but we have not taken into consideration the effect of the intervening atmosphere upon the lines, lights, and colors. If there were no air at all there might still be linear perspective, as we all have noticed in those huge airless landscapes which are sometimes hippo dromed around the world for the admiration of the unthinking many ; but in thoroughly good painting the air must be reckoned with, for it changes the appearance of objects quite as much as simple form-shrinkage.
Atmosphere must be looked upon as something in the nature of a mist, a haze, or a light smoke. The air about us is filled with countless particles of matter, which reflect, break, and transmit waves of light in such a way that when in quantity we see them as a blue or a gray haze. Hence the azure of the sky overhead and the blue-gray appearance that hangs about the mountains, or in the far-away depths of their valleys. This haze, though too sub-tile of itself to be seen at, say one hundred yards, has a very decided effect upon objects at that distance which may be readily observed. This effect is, first, that while the objects recede in size they also begin to blur and waver in outline. An indistinctness gathers about them, similar, though not so strong, to the dimness which enshrouds objects at evening when the light begins to fade.
We have not an active appreciation of this be-cause we lack the keen eyes of painters, and for the further reason that we have a mental knowledge of almost all the objects of nature which continually contradicts our visual knowledge. Thus we recognize at two hundred yards down the street a friend coming toward us ; but how do we recognize him ? Simply because he is a friend ; because we mentally know, from having stood beside him many times, just how he looks in face and feature. We see him on the street ; something in circumstance, dress, carriage, or height speaks who he is, and then our accommodating mind, knowing his features, tells our eyes just what those features are like, and we immediately fancy we see his brown eyes, his Greek nose, and his clean-cut chin. The mind may be right enough in its recollection, but the eyes have been deceived ; for at that distance the human face, especially under the shadow of a hat-brim, is little more than a blur of flesh color. The legs, arms, body, head, are seen, but the features of the face, sometimes the hands and feet are goneblurred outnot by reduction in the size of those features, but by seeing them through a veil of atmosphere which dissipates and obscures their lines. The truth of this illustration I will ask you to test by trying to make out the features of a person whom you have never seen before, at the distance I have supposed. Under gaslight you require a glass to see features distinctly across an opera-house ; you will need the same glass under sunlight to see the same features on the street at two hundred yards.
We may make a similar mistake in landscape. We go out into the meadow, and before our feet it is an easy matter to count the individual blades of grass as they grow ; fifty yards away we know similar individual blades exist, and perhaps fancy we can see them but do we? A hundred yards farther on is a tree in foliage ; we know foliage is formed of separate leaves, and again we fancy we can see these leaves ; but all that our eyes tell us is summed up in a round mass of green, broken by lights and shadows. Several hundred yards farther on are some sheep browsing in the grass. Try to see their ears ; try to make out their legs ; try to make out if they have heads. You cannot. The animals are only oblong patches of dark or light color against the green background.. Suppose the distance increased several hundred yards more till the sight strikes a belt of timber. It is composed of individual trees with broad trunks and many limbs ; can you distinguish any one of them? Is there anything to the timber but a mass of green and purple foliage impenetrable to the eye ? And so we may keep on increasing the distance until we come to the mountain, around the base of which, like a flat carpet, run forests of timber scarcely recognizable except by our mental knowledge that they are forests ; and higher up come gray and bluish masses which we know to be huge forms of granite standing aloft like the castles of the Rhine ; and still higher up in the slopes and gorges the blue air becomes so dense that the timber, the rocks, sometimes parts of the mountain itself, are lost to view.
Occasionally in Iooking at the mountain, when the weather is clear, you may observe what may seem at first blush a singular phenomenon. The trees at the base of it are very dull in color and vague in line, but at the top they appear to come out more distinctly. The top appears nearer to you than the bottom. This may be partly due to the fact that the timber grows thinner toward the summit, and is thus more distinct ; but it is mainly due to the very thing I am trying to illustrate, namely, the density of the air. The base of the mountain is seen through that mass of the thick air which always lies close to the ground ; the top is partly seen through a higher and thinner atmosphere. It is the school-teaching of to-day that the seeing on the ocean of a vessel’s masts and sails before seeing her hull is a proof of the roundness of the earth. The teaching is true enough, but in actual demonstration it may be questioned if the interposition of the dense atmosphere lying along the water has not quite as much to do with losing the ship’s hull as the interposition of the earth’s surface. The painting of distant ships in the marine pieces of Dupre, Boulard, and others, argue that way at the least, and in a matter of actual appearance a painter’s eye is quite as reliable as a mathematician’s figures.
Form, then, not only shrinks in size in proportion to the distance removed, but blurs and wavers and loses its outline in proportion to the density of the atmosphere through which it is seen. On a clear day, or in high altitudes, lines are quite distinct as are the stars on a cold winter night ; in the haze of October, the mist of spring, the heat of summer, they dissipate more rapidly. In a fog, such as we often know along the Atlantic seaboard, a few yards are sometimes sufficient to lose the form of objects altogether, as you may have noticed in the ease of coming and going ferryboats in New York harbor during foggy weather. And, by the was, I may call attention here to the fact that the tops of these ferryboats are almost always seen before the hulls or guards, a fact which may serve as further argument in the ship-at-sea question. Fog is only an extreme illustration of atmospheric density, the air being filled with atoms of moisture instead of, as upon a clear day, with atoms of dust. One is denser and more perceptible than the other, and has a more positive effect upon line ; but both of them are modifying influences which the painter estimates in giving distance, and which we should be careful to note for the reason that the tyro in painting often fails to note them.
Yet line is not the only thing that dissipates and blurs in proportion to the density of the atmosphere through which it is seen. Color is an important part of objects, and this, too, is changed by air in more ways than one, and often to the painter’s perplexity. First, let me say that, so far as I have observed, I do not find that colors, as colors, are capable of rendering distance by association or otherwise. That is to say, blue, because it resembles the sky or the ether around distant hills, is not a distance color ; nor red, because of its warmth or frequent use in household decoration, a near color. All colors are affected by distance, but they do not of themselves create it, as seems to be supposed in some quarters. In original hue one appears about as near or as far as another. In the order of their disappearance in the distance there may be a difference ; but, after asking many landscape painters about this, and making not a few experiments and observations myself, I am inclined to doubt if there be any great or well-defined difference. There is an apparent variance which may be due to causes other than hue or atmospheric effect, the quantity of light or dark contained in a color in connection with the background against which it is seen being the principal one. Given similar intensities of green, yellow, and bluethat is, make them equal in the quantity of light or dark they shall containplace them on an absolutely neutral background, and one will appear about as strong as another. But if the intensities of light or dark be unequal in the colors, as, for instance, in a chrome-yellow, an emerald-green, and a cobalt-blue, then that color will (practically) disappear first which shows the least contrast to the background. If the background in the case of these supposed colors should be a green meadow, then the emerald-green would go first, the cobalt-blue second, and the chrome-yellow last, the light of the yellow standing out in the strongest re-lief against the dark of the green ground.
It seems to be the opinion of some writers, Leonardo da Vinci among others, that the dark colors carry stronger than the light ones ; but, with great respect for Leonardo, I think the working of the rule is mainly dependent upon this same matter of background again. A light shows better on a dark ground, and a dark better on a light ground. A practical illustration of the first statement is the white disk on the line-poles used in surveying, the white showing stronger against green landscape than black. An illustration of the second may be seen by flying two kites, one a deep purple and the other a pale yellow, against a light sky. The purple kite will stand out the longer, and the stronger by contrast. A double illustration may again be found in the military system of signalling by flags. If signalling from a hill-top five miles away, where the light sky is the background, a black or red flag is used ; if signalling in a valley where the dark earth is a background, a white flag is used.