PERSPECTIVE.
(Vol. ix., p. 300.)
Your correspondent Mr. G. T. Hoare is rather bold in describing the case he does as a "very common error;" and I cannot agree with him that the façade of Sennacherib's Palace (Layard's 2nd book on Nineveh) is an instance of the kind. The theory that horizontal lines in the plane of the picture should converge to a point on the horizontal line right and left of the visual ray, is by no means new; in truth, every line according to this view must form the segment of a circle more or less, according to circumstances. Apply this principle to the vertical lines of a tower or lofty building, and every such structure must be represented diminished at the top, the vertical lines converging to a vanishing point in the sky.
Some years since, this theory was brought forward by Mr. Parsey, and the subject fully discussed at scientific meetings. There was much ingenuity in the arguments employed, but the illustrations were so unsatisfactory that the system has never gained ground. The principles of perspective are most ably exemplified in many well-known works, as they set forth very satisfactory modes of delineation. The limits of your periodical prevent a fuller correspondence on this subject, or I think it would not be difficult to
satisfy Mr. Hoare that there are great difficulties attending his proposition.
No recent discoveries in the art of perspective have tended to more truthful representations than those produced by the recognised systems usually adopted. The method of showing the internal courts, &c. of large groups of buildings by isometrical perspective, although very useful for developing architects' and engineers' projects, is not a system that will bear the test of close examination.
Benj. Ferrey.
G. T. Hoare is quite right in saying "that every line above or below the line of the horizon, though really parallel to it, apparently approaches it, as it is produced to the right or left." But he seems to forget that the same holds good in the picture as in the original landscape, the part opposite the eye being nearer to it than the margin of the paper. To produce the same effect with converging lines, the drawing must be made to assume the form of a segment of a circle, the eye being placed in the centre.
John P. Stilwell.
Dorking.
I must beg leave to differ most decidedly with Mr. G. T. Hoare on this point. If it is in accordance with the principles of perspective that, supposing the eye and the picture in their true positions in relation to each other and to the objects represented, every line drawn from the eye to any point of a real object will pass through its corresponding point in the picture, then the supposed wall will form the base of a pyramid, of which the eye will be the apex, and the representation of the wall in the picture a section parallel to the base, and consequently mathematically similar to the base itself. It is perfectly true, as Mr. Hoare says, "that every line above or below the line of the horizon, though really parallel to it, apparently approaches it, as it is produced to the right or left." But he forgets that this fact applies to the picture as well as to the object. In fact, the picture is an object, and the parallel lines in it representing the wall must have the same apparent tendency to one another as those in the wall itself.
Ἁλιεύς
Dublin.
I am glad Mr. G. T. Hoare has called attention to the defective state of the art of perspective. His remarks, however, are too narrow. The fact is, that any two parallel straight lines appear to converge at one or both ends, and one or both lines assume a curvilinear shape. For a notable example, the vertical section of the Duke of York's column in Waterloo Place, from all points of view, appears to bulge at the point of sight, and to taper upwards by a curvilinear convergence of the sides.
C. Mansfield Ingleby.