In any case, let us keep well in mind the different symbolism implied by curves, angles, straight lines, and circles. Squares and oblongs denote repose and weight, while circles and curved lines are identified with everything in the universe that denotes life, mystery, intelligence, fertility, light and heat, movement and speed, and space illimitable. Human progress itself is a circular ascent along the finest spiral lines, for civilization as a whole never comes back to the same conditions, but creeps above them to some trivial extent. The greatest circular or rounded shapes are the sun, the full moon, our own little world, the human skull, and the human heart; eggs, flowers, nests, the shapes of bones, and the wheel, without which dilatory progress would have been far and away too pedestrian. The first wheel was a rolling stone; afterwards men noticed that a log touched by accident on a hill rolled down for some distance; and at last a person of genius cut solid sections from a tree-trunk and made the earliest wheel of handicraft. Just one more point ought to be noticed with sympathetic care: that arches in art are more suggestive than circles; they have the mystery of a beautiful part taken from a whole--a whole that looks methodical. We feel this mystery whenever we watch how the moon grows from a silver crescent into a radiant circle. A thing complete dulls an attention that looks on, whereas growth or the suggestion of growth has the stimulus of hope and faith. To culminate is to begin a decline. Even the circle of the sun would be tiresome but for the grey days that renew a truism into a gracious truth. This explains why arches in art make an appeal to the imagination that circles never equal. For example, wheel-windows in Gothic architecture never have the magic of pointed windows. Our eyes travel around them and cannot escape in a flight upwards. Nature, then, when she produced arches, brought into the world a very noble inspiration, and therefore very remote from the dull and slow mimicry of mankind.