"To institute a fair comparison between terminated lines and figures, the component lines of the figures should be as beautiful as the terminated lines with which they are compared. With this precaution, physiology will conduct to the conclusion, that figures are more beautiful than terminated lines. For the survey of any figure requires the successive action of all these ocular muscles, and a repeated survey requires no reversal of the motion. "We may apply the same principles to _figures as compared with each other_. Here we shall find the advantage on the side of those which are geometrically regular. We perceive that the circle and ellipse must possess in great perfection the essentials of beauty. "From figures, the transition is natural and easy to _solids_ or bodies of three dimensions. The form of a body depends on those of all its faces and sections; and these last are plane figures. The elliptical sections of a regular spheroid are all highly beautiful, but its sections are not all elliptical. Unless the spheroid be in certain positions, the sphere possesses still higher beauty, as presenting the same circular and highly beautiful outline in every position; although a variety of positions is not essential to the perception of its peculiar beauty, whenever the observer has learned by different methods, and especially by different degrees of convergence of the two optic axes, to estimate the relative distances of the different points of the visible hemisphere, and thus to recognise the spherical form. I will only add, from the analysis of the beauty of the circle it is evident, that within certain limits, to magnify a sphere is to magnify its beauty. "The relative beauty of the sphere and spheroid, and of the spheroid as compared with itself in different positions, is modified by _symmetry_. The principle of symmetry, is in some measure distinct from any other heretofore considered. It may be treated under the heads of 1st, geometrical symmetry, or symmetry of form; 2d, of symmetry of position.