Illustrations of its Effects. 615 intervals of clear blue between them, may appear to a spectator, anywhere on the ground, to form, towards the distant horizon, a dense unbroken bed. 846. If a man standing on a hill look down upon a field or plain which is known to him, and if he see some objects near its side, and some near its middle, and some near its distant border, he judges fairly by the angles how far they are from him and from one another. Similarly, when viewing the ocean from a lofty peak, and seeing ships scattered over its face, he judges tolerably of their distance, for he can see only a certain extent of ocean which becomes to him as a known field. The man stationed at the flagstaff on the High Knowl of the island of St. Helena, looks down upon a circular field of the Atlantic, a hundred miles broad, and can tell the distance of any sail in sight to within a few miles. Although the ground plan of an extensive landscape may not be so level as the face of the ocean, there is still an approximation, which considerably assists a spectator's judgment of dimensions. Painters are careful not only to foreshorten, according to the proportions explained above, all the objects seen obliquely which they portray, but they avail themselves of this principle to produce very striking effects. For instance, the accomplished Martin, the painter of Belshazzar's Feast, in many of his beautiful designs, by judicious foreshortening, exhibited miles in extent of gorgeous architecture and of armed men, on a very small extent of canvas: he made a single magnificent pillar or accoutred warrior in the foreground, serve as the type which first warmed the mind with admiration, and then sent the conception along retiring lines of beautiful perspective, where every tip or edge renewed the first impression. A man lying on a high table or bed, with his feet towards the spectator, is foreshortened into a roundish heap, of which the soles of the feet hide the greater part. This is the description of the painting which was called the "Miraculous Entombment," in viewing which an unreflecting spectator, while moving sideways, with the expectation of seeing more of the body, still saw only the soles of the feet, and could suppose the body to be turning round so as to eep the feet towards him. For nearly the same reason, the eyes of a common full-face portrait, may seem to follow a spectator while going to different parts of the room,-for by moving to a side of the picture he cannot see the side of the eye-balls. A rifleman portrayed as if taking aim directly in front of the picture, appears to every spectator to be pointing at him specially. 516 The Rules of Perspective. 847. As the painter, availing himself of a knowledge of the prin ciples now explained, by which the eye usually judges of size and distance, may produce on his canvas charming illusions, so may the tasteful proprietor of ornamental gardens and pleasure-grounds, by working his solid levels into artificial undulation of hill and dale, and clothing these with tree and edifice of magnitudes to correspond-make the eye of a spectator contemplate supposed extensive plains, lofty mountains, spacious lakes, and distant pagodas-all within the narrow space of a few acres ; so, by another set of means, producing on the eyes of observers nearly the same impressions as Claude, Poussin, or Turner have given by their noble pictures. When the representation of any object or mass of objects is foreshortened, because one part has to appear farther from the eye than another, that part is made in a proportion smaller than equal parts nearer. For example, in a straight row of similar houses, pillars, or trees (see fig. 205), those nearest to the eye will, on a pane held before the eye to receive their light, occupy the larger space, and there will be a gradual diminution from the largest to the least, so that lines drawn upon the glass along the tops and bottoms of the images would tend to a point, called, for a reason to be explained below, the vanishing point. Thus a person looking from a window along a straight street, must, in order to see the chimneys of the nearest house, look through the top of the window, and to see the street door must look through the bottom; but the most distant house, both top and bottom, is to be seen through a small extent of the glass level with the height of the eye. This remarkable tapering of foreshortened objects may of course be strikingly observed on looking at any correctly-made drawing or engraving intended to represent a retiring row of similar objects;—such drawing being, in truth, an attempt to realize by art, on the surface of a sheet of paper, the appearance of the objects as seen through a window or aperture of the size of the paper; or, as would be seen on the glass of a window, if rays of light could leave marks in passing. 848. Perspective.-The art which gives rules for tracing objects on a plane surface, as they would appear to an eye looking at them through that surface if transparent, with their various degrees, first, of apparent diminution, on account of distance, and, secondly, of foreshortening, on account of the obliquity of view, is called, from the Latin word, perspicio, signifying to look through, the art of perspective. It regards chiefly the two particulars now mentioned; and, notwithstanding the terror with which, in the imagination of The Vanishing Point. 617 many young painters, the study of it is clothed, by reason of the mathematical difficulties with which it has usually been surrounded, it is in itself very simple. A student can scarcely make a more instructive experiment than to take a framed drawing or engraving of a view from some window, and having set it up near the window, to place by its side an empty frame of the same size. By then comparing the reality, viewed as a picture, through the empty frame, with the true picture fixed in the other, their perfect accordance becomes very striking in regard to the sizes, positions, and shadings of the parts, all illustrating the rules of perspective. Although, without a knowledge of these rules, a quick eye soon enables its possessor to sketch from nature with much truth; and although the two instruments, the camera obscura, already described, and camera lucida, to be described in a future page, give almost mathematical accuracy to drawings made with their help, without requiring other skill in the draughtsman than to trace and make permanent, with ink or pencil, the lines of light which he sees on the paper; still the subject is so interesting to all who attempt to sketch, and, indeed, to all who wish to look intelligently either at nature or at works of art, that none who have the opportunity of studying it, should neglect the study. Supposing straight rows of similar objects, as of the stone blocks, or pillars, or houses represented in fig. 205, from a or b to S, to run Fig. 205. directly south, and to be viewed by a person stationed at a window over the point, C, between and near the end of the rows forming the street, f, d, then, because, as already explained, objects to the eye 618 The Vanishing Point appear smaller in proportion to their increased distance from it, the second block, if twice as far off as the first, would appear only half as large; the third, if three times as far, would be only one-third as large, and so on to any extent, and for any other proportions; and if the thousandth or any other block, owing to its distance, subtended to the eye an angle less than the sixtieth of a degree of space in the field of view, it would be altogether invisible, even if nothing intervened between it and the eye. For the same reason that the size of the blocks would appear smaller, the distance between corresponding or opposite blocks in the two rows, would appear less and less, until the rows would seem to meet. Then, where the rows and the blocks cease to be visible from the minuteness of the parts and distances, and from the fact of the nearer ones concealing those farther off, they are said to have reached their vanishing point. When a student of perspective has learned what regards the vanishing point in relation to sizes, distances, and positions of objects, he has learned half of his art. The above cut is to be considered as the representation of a street, running directly south to S, sketched from a window opposite to its end looking along its centre. 849. It is important here to remark, that in any case of a straight line, or a row of objects thus vanishing from sight, as here the line or row, a S, in whatever direction it lies from its beginning, whether east, west, north, or south, in that direction, exactly from the eye of the observer, will its remote or vanishing extremity disappear. In this sketch the row a s. is supposed to run directly south; and, although the eye, to see the beginning or near end of it, would have to look towards the left or east end, and to see the first block of the other row would have to look west, still every successive pillar would appear more and more towards the south, and the point in the heavens, or in a picture, or in a transparent plane before the eye, where the lines would vanish, would be exactly south from the eye. Then, similarly, if there were many rows of objects, as of pillars, houses, or trees, parallel to the first, but considerably apart from each other, as the lines, a s, b s, d s, still all would vanish, or seem to terminate, in the very same point of the field of view. 850. The reason of this important fact may be thus explained :Let us suppose a line drawn directly south from the eye to the point S, between the parallel lines of pillars, houses, and trees, a s, b s, d s, also pointing directly south, and let us suppose the two rows of pillars to be ore hundred feet apart, then evidently for the same reason as the of Parallel Lines. 619 space between the top and bottom of the pillars, that is to say, their height, becomes apparently less and less as their distance from the eye increases, so will the space between each pillar and its opposite in the other row, or between it and the point corresponding to it in the visual ray along which the eye looks, become apparently less, and therefore the lines of pillars, really and everywhere 100 feet apart from each other, and 50 feet from the visual ray, will, at a certain distance from the eye (viz., where a space of 50 or 100 feet is apparently reduced to a point), appear to join, and the three lines will appear to meet in that point, beyond which none of them can be visible, and which is therefore the vanishing point of all. It aids the conception of this truth to suppose a planet visible in the exact point of the heavens, S, at the moment of observation; then, if the three parallel lines were continued on to the planet, and were visible all the way, they would arrive there with the interval between them just as when they left the earth; but as a planet, although thousands of miles in diameter, owing to its distance from the earth, appears on earth only as a point, much more would two lines only 100 feet apart be there undistinguishable in place by human sight. What is true of a space of 100 feet between parallel lines, is equally true of a space of a mile or of thousands of miles. As a general rule, therefore, it holds, that all lines really parallel among themselves, when represented in perspective, tend towards, and if continued, end in, the same vanishing point-which point is the situation where the line terminates, along which the eye looks when directed parallel to any one of the real lines. This is true not only of lines lying in the same level or horizontal plane, such as might be formed across a lake, but also of lines placed one above another, as those running along the tops and bottoms of the pillars here, or along the walls, roofs, and windows of the houses, or along the roots and summits of the trees, and indeed of all lines in whatever situation, provided they are parallel to one another, and therefore to the visual ray. This truth holds equally with respect to short lines which do not reach the vanishing point, or centre of the picture, as with respect to those which do. When it is ascertained therefore that a line or boundary of any natural or artificial object has a certain inclination to the axis of the picture, or to what we have described as the principal visual ray, then also is it known that all the parallels to that line have their vanishing point in the same spot of the field of view, and a line supposed to be drawn from the eye into space, or really drawn from the eye to the picture in |