PERSPECTIVE, the science of repro senting appearances, and as such is op posed to geometry, which is the science of representing facts. It is founded up on such rules as can be deduced from the facts which are discovered by looking at objects through a sheet of glass or other transparent medium placed upright be tween the object and the observer. It is found when objects are so looked at that their apparent form is very different from their real one, both as regards shape and distinctness. The portion of the subject which deals with the changes in form is absolutely scientific; it is called linear perspective. The changes in distinctness are effected by distance and atmosphere, and differ constantly with different conditions of light and at mosphere. It is the purely artistic side of the science which is called aerial per spective, and success in its application depends on the individual ability of the artist. The chief point with which linear perspective has to deal is the apparent diminution in size of objects as they re cede from the spectator. A practical
knowledge of the science is absolutely a necessity for a successful artist.
A kind of painting designed expressly to deceive the sight by representing the continuation of an alley, a building, a landscape, or the like. Oblique (or angular) perspective, where the plane of the picture is supposed to be at an angle to the side of the principal object in the picture, as, for instance, a building. Parallel perspective, where the plane of the picture is parallel to the side of the principal object in the picture. Perspec tive plane, the surface on which the ob jects are delineated, or the picture drawn. It is supposed to be placed vertically be tween the eye of the spectator and the ob ject. Also termed the plane of projec tion, or the plane of the picture.