knows that the
sweetness of fruit is caused by a subtle oil, and such a salt as that
mentioned in the last section. Afterwards custom, habit, the desire of
novelty, and a thousand other causes, confound, adulterate, and change
our palates, so that we can no longer reason with any satisfaction about
them. Before we quit this article, we must observe, that as smooth
things are, as such, agreeable to the taste, and are found of a relaxing
quality; so on the other hand, things which are found by experience to
be of a strengthening quality, and fit to brace the fibres, are almost
universally rough and pungent to the taste, and in many cases rough even
to the touch. We often apply the quality of sweetness, metaphorically,
to visual objects. For the better carrying on this remarkable analogy
of the senses, we may here call sweetness the beautiful of the taste.

SECTION XXIII.

VARIATION, WHY BEAUTIFUL.

Another principal property of beautiful objects is, that the line of
their parts is continually varying its direction; but it varies it by a
very insensible deviation; it never varies it so quickly as to surprise,
or by the sharpness of its angle to cause any twitching or convulsion of
the optic nerve. Nothing long continued in the same manner, nothing very
suddenly varied, can be beautiful; because both are opposite to that
agreeable relaxation which is the characteristic effect of beauty. It is
thus in all the senses. A motion in a right line is that manner of
moving, next to a very gentle descent, in which we meet the least
resistance; yet it is not that manner of moving, which next to a
descent, wearies us the least. Rest certainly tends to relax: yet there
is a species of motion which relaxes more than rest; a gentle
oscillatory motion, a rising and falling. Rocking sets children to sleep
better than absolute rest; there is indeed scarcely anything at that
age, which gives more pleasure than to be gently lifted up and down; the
manner of playing which their nurses use with children, and the weighing
and swinging used afterwards by themselves as a favorite amusement,
evince this very sufficiently. Most people must have observed the sort
of sense they have had on being swiftly drawn in an easy coach on a
smooth turf, with gradual ascents and declivities. This will give a
better idea of the beautiful, and point out its probable cause better,
than almost anything else. On the contrary, when one is hurried over a
rough, r