Dr. M. Foster says in his “Text-Book of Physiology,” sec. ii., on Binocular Visionthat “when we use both eyes a large part of the visual field of each eye overlaps that of the other; but that, nevertheless, at the same time, a certain part of each visual field does not so overlap any part of the other. The dimensions of the field of sight for one eye will, . . . be approximately circular.” But, so far as this is true, notice that the whole field of sightnot for one eye, but for both eyes when acting conjointlyis represented neither by the single circle . . . nor by . . . two separated circles; but rather by the space enclosed between . . . two circumferences of the circles where they overlap,
This space has the shape termed by botanists elliptic lanceolate,an ellipse pointed; and of all outlines wholly curved, those of an upright ellipse fit into it most nearly.
The bearing of this upon our present subject is found in the fact that the whole of a form facing us can be recognized with ease, i. e., in a single glance, or, at least, a single conscious glance, in the degree in which it is conformed to vertical elliptic-lanceolate outlines. Indeed, this fact thus theoretically unfolded, can be confirmed by practical experiments. If we describe at the nearest point at which it is posible to perceive all its outlines, an ellipse longer vertically than horizontally, and about it a circle of the same diameter as the vertical length of the ellipse, there will be not a few who will find it slightly more easy at a single glance, or with-out consciously changing the axis of the eye, to perceive all the outlines of the former than of the latter. If we describe about the circle and ellipse a square of the same diameter as the circle, no one can see all its outlines without consciously changing the axis of the eye, as when glancing from corner to corner; and if we describe about the square a rectangle of the same vertical but twice the horizontal dimensions, we cannot see all its outlines without changing the axis still more consciously.
In the use of the eyes, the difference between movement and no movement, or no conscious movement, is the difference between activity, work, or effort, and rest, play, or enjoyment. But this is the same difference as in Chapter III. of this book is said to separate that which is done with a utilitarian aim and an aesthetic. If a form of outline naturally fitting into the shape of an upright elliptical figure, be the one which requires, to recognize it, the least visual activity, work, or effort, then this form must be the one most conformed to the physiological requirements of the eye. In other words, it is the form most in harmony with these requirements; therefore the most agreeable, the most pleasurable, the most “fitted to be perceived,” which is the exact etymological meaning of the word aesthetic. This fact furnishes the best possible justification for calling the curveparticularly, as we shall notice presently, the one found in the ellipsethe line of beauty.
What has been thus found to be true with reference to the elliptical contour, renders significant many whole classes of facts with which few of us can fail to be familiar. Recall, for instance, the extensive use in art of this elliptical shape. If we go into the shops where they sell implements for drawing, whatever else they may not keep, assortments of models for different sizes of ellipses are sure to meet our eyes. The one ornamental object, avowedly not modelled after an appearance in nature, which the arts of all lands and races have united in producing, is the vase; and this is almost invariably conformed to vertical elliptic-lanceolate outlines. Again, in architecture, the form that general usage has shown to be the most satisfactory is one which, whether we consider it as exemplified in the cupola or the dome, is . . . described within the space enclosed between circles . and even if the building be wide, the form preferred for this is one containing at least a central part which . . . it is possible to enclose in such a space. Notice, too, how the human form as a whole fits into the same elliptic-lanceolate shape.The Essentials of Aesthetics, XVI.