The art of delineating objects on any given surface as they would appear to the eye if that surface were transparent, and the objects themselves were seen through it from a fixed situation. Thus, if on looking through a window at any object we were to trace over all the lines of the object on the glass, carefully keeping the eye in precisely the same position all the time, we should make a perspective drawing of the object, and the glass would be termed the plane of delineation. Every true perspective picture is, therefore, an exact copy of the order in which the rays, proceeding from the object represented, would intercept in their passage to the eye a transparent plane at right angles to the direction in which the eye viewed that object; which plane is the plane of delineation of the picture, which is large or small, according to its distance from the eye. It does not form a part of the plan of this work to give a treatise on the art of drawing in perspective; and the foregoing observations have been chiefly made as introductory to the next article