This seems to me so evident, that I am a good deal surprised that none who have handled the subject have made any mention of the quality of smoothness in the enumeration of those that go to the forming of beauty.

For, indeed, any ruggedness, any sudden, projection, any sharp angle, is in the highest degree contrary to that idea.
SECTION XV.
GRADUAL VARIATION.
But as perfectly beautiful bodies are not composed of angular parts, so their parts never continue long in the same right line.[25] They vary their direction every moment, and they change under the eye by a deviation continually carrying on, but for whose beginning or end you will find it difficult to ascertain a point.

The view of a beautiful bird will illustrate this observation.

Here we see the head increasing insensibly to the middle, from whence it lessens gradually until it mixes with the neck; the neck loses itself in a larger swell, which continues to the middle of the body, when the whole decreases again to the tail; the tail takes a new direction, but it soon varies its new course, it blends again with the other parts, and the line is perpetually changing, above, below, upon every side.

In this description I have before me the idea of a dove; it agrees very well with most of the conditions of beauty.