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tions of them, as I have shewn in a preceding chapter. It is peculiarly defective when applied to parts of bodies at different distances from it, and of a less diameter than the lens. The photograph of a cube taken by a lens of a greater diameter, will display five of its sides in a position, when its true perspective representation is simply a single square of its surface. When applied to trees, and shrubs, and flowers, its pictures are still more unsatisfactory. Every stem and leaf smaller than the lens, though absolutely opaque, is transparent, and leaves and stems behind and beyond are seen like ghosts through the photographic image.
This will be understood from Fig. 48, in which Ll is the
lens of the camera, Ab the breadth of the trunk or stem of a tree less than Ll in width. Draw La, Lb, touching Ab in the points A, B, and crossing at c. Objects behind Ab, and placed within the angle Acb, will not have any images of them formed by the lens Ll, because none of the rays which proceed from them can fall upon the lens, but objects placed within the angle Ecf, however remote be their distance, will have images of them formed by the lens. If D, for example, be a leaf or a fruit, or a portion of a branch, the rays which it emits will fall upon the portions L»i, Ln of the lens, determined by drawing Dm, Dn touching Ab, and an image of it will be formed in the centre of the photographic image of a b, as if A B were transparent. This image will be formed by all the portions of the surface of the lens on which the shadow of Ab, formed by rays emanating from D, would not fall. If the object D is more remote, the shadow of Ab will diminish in size, and the image of the object will be formed by a greater portion of the lens. If the sun were to be in the direction M N, his image would appear in the centre of the trunk or stem, corresponding to Ab, Fig. 49.
images of them formed within the corresponding portion of the trunk or stem. Hence, if Ab, Fig. 49, represents the shadow of the stem across the lens Ll, the image of any object, which if luminous would give this shadow, will be formed within the photographic image of the stem, and as every part of it may have branches, or leaves, or fruit behind it, its photographs will be filled with their pictures, which will have the same distinctness as other equidistant parts of the landscape.
These observations are applicable to the limbs and slender parts of animate and inanimate figures, when they are of a less size than the lens with which their photograph is taken. They will be transparent to all objects behind them, and their true forms and shades cannot be taken with the cameras now in use.1
In order, therefore, to collect from nature the materials of his profession, the artist must use a camera with a lens not much larger than the pupil of his eye, and with such an instrument he will obtain the most correct drawings of the trunks and stems of trees, of the texture and markings of their bark, of the form of their leaves, and of all those peculiarities of structure and of leafage by which alone the trees of the forest can be distinguished. In like manner, he will obtain the most correct representations of the rocks and precipices, and the individual stones2 which may enter
1 By using large lenses, we may obtain the picture of an object within the picture of an opaque one in front of it; and with a telescope, we may see through opaque objects of a certain size. Many singular experiments may be made by taking photographs of solid objects, simple or compound, with lenses larger than the objects themselves.
2 In a landscape by Mr. Waller Paton, called the "Highland Stream," now in the Edinburgh Exhibition, the foreground consists principally of a bed of waterworn stones, on the margin of a pool at the bottom of a waterfall. The stones are
into his picture,—of the plants which spring from their crevices or grow at their base, and of those flowers in their native grace and beauty, which hitherto he has either drawn from recollection, or copied from the formal representations of the botanist.
In addition to their correctness as true representations of natural forms, photographs have a peculiar value, for which no labour or skill on the part of the artist can compensate. In drawing the sketch of a landscape, or delineating the trees, rocks, and foliage which are near him, or the objects in the middle or remote distance, several hours must be spent. During this period, the landscape and its individual parts are undergoing no inconsiderable change. A breeze may disturb the masses of his foliage, and bend his tree stems, and ruffle his verdure, and throw new reflected lights upon the waving crops, while every direct light is changing in intensity and direction during the culmination or descent of the sun. What he has delineated in the morning will hardly correspond with what he draws at noon, and the distances which at one time are finely marked in aerial perspective, will disappear, or even suffer inversion by variations in the intensity and position of the haze. If cottages, or castles, or buildings of any kind, enter into the picture, the shadows of their projections, and the lights upon their walls and roofs will, in sunshine, undergo still greater variations, and the artist will be perplexed with the anachronisms and inconsistencies of his choicest materials. The landscape thus composed in patches will, in its photograph, have a very different aspect, as much in its forms as in its lights and shadows. The truths of nature are fixed at one instant of time; the self-delineated landscape is embalmed amid the co-existing events of the physical and social world. If the sun shines, his rays throw their gilding on the picture. If the rain-shower falls, the earth and the trees glisten with its reflexions. If the wind blows, the partially obliterated foliage will display the extent of its agitation. The objects of still life, too, give reality and animation to the scene. The streets display their stationary chariots, the esplanade its military array, and the market-place its colloquial groups, while the fields are studded with the forms and attitudes of animal life. The incidents of time and the forms of space are thus simultaneously recorded, and every picture from the sober palette of the sun becomes an authentic chapter in the history of the world.1
so exquisitely painted, that nature only could have furnished the originals. We may examine them at a few inches' distance, and recognise forms and structures with which we have been long familiar. A water-ousel, peculiar to Scottish brooks and rivers, perched upon one of them, looks as anxiously around as if a schoolboy were about to avail himself of the missiles at his feet.
But, however valuable photography has become to the artist, science has recently given him another important auxiliary. In order to make this available, he must employ a small pocket binocular camera, to take double pictures to be united in the stereoscope. His trees will thus exhibit the roundness of their trunks and stems, the leaves and branches will place themselves at their proper distance, and he will discover the reason of peculiar effects which in the plane photograph he has been unable to understand. Seeing that his own picture is to be upon a plane surface, I can hardly expect to convince the artist that he will obtain more information by reproducing the
1 These views are well illustrated by the remarkable photographs of the Crimean