Practical Essays on Art

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1893 ...is parallel with the base line, until it is viewed upon the angle; the cause of this perhaps may be more clearly explained by fig. 90. Fig. 90. Suppose the circle to represent the line of the horizon, which is the true representation of it when viewed out at sea, or where no obstruction intercepts it, for then the water coming in contact with the sky, presents a circular horizontal line. If a person, therefore, was placed at D, and looking to the point A, the line c would be parallel with the base, being at right angles with A, and consequently occupying one-fourth of a circle; but if he turned in the direction of B, then A and c would become vanishing points, though still at equal distances upon the horizontal line, and would appear thus, Fig. 91. In a panorama, which is a circular canvas, viewed from the centre, this mode of measuring the various points is found to agree perfectly with the natural representation of objects. CIRCLES. If anyone takes a drinking glass or cup in his hand, with the mouth of it towards him, and gradually turn it from him, carefully watching it passing through all the elliptical forms until the brim becomes a straight line in appearance, he will have a correct idea how it is that columns, or other circular objects, assume an oval shape at the top or bottom, according as they are below or above the eye. Or if he holds the cup with the side downwards, and turns the mouth gradually round towards him, he will perceive the cause why Fig. 93. arches, or circular gateways, appear elliptical in a side view. It arises from parts of the circle being more foreshortened than other parts; that is to say, those parts which come more in the line of the visual rays. For example, let a circle be divided into equal parts, and suppose the eye of t...