and others turn their backs upon him,
to show their unagitated faces to the spectator.

Sec. 9. And towards unity of sequence.

In unity of sequence, the effect of variety is best exemplified by the
melodies of music, wherein by the differences of the notes, they are
connected with each other in certain pleasant relations. This connection
taking place in quantities is proportion, respecting which certain
general principles must be noted, as the subject is one open to many
errors, and obscurely treated of by writers on art.

Sec. 10. The nature of proportion. 1st, of apparent proportion.

Proportion is of two distinct kinds. Apparent: when it takes place
between qualities for the sake of connection only, without any ultimate
object or casual necessity; and constructive: when it has reference to
some function to be discharged by the quantities, depending on their
proportion. From the confusion of these two kinds of proportion have
arisen the greater part of the erroneous conceptions of the influence of
either.

Apparent proportion, or the sensible relation of quantities, is one of
the most important means of obtaining unity between things which
otherwise must have remained distinct in similarity, and as it may
consist with every other kind of unity, and persist when every other
means of it fails, it may be considered as lying at the root of most of
our impressions of the beautiful. There is no sense of rightness, or
wrongness connected with it, no sense of utility, propriety, or
expediency. These ideas enter only where the proportion of quantities
has reference to some function to be performed by them. It cannot be
asserted that it is right or that it is wrong that A should be to B, as
B to C; unless A, B, and C have some desirable operation dependent on
that relation. But nevertheless it may be highly agreeable to the eye
that A, B, and C, if visible things, should have visible connection of
ratio, even though nothing be accomplished by such connection. On the
other hand, constructive proportion, or the adaptation of quantities to
functions, is agreeable not to the eye, but to the mind, which is
cognizant of the function to be performed. Thus the pleasantness or
rightness of the proportions of a column depends not on the mere
relation of diameter and height, (which is not proportion at all, for
proportion is between three terms at least,) but on three other involved
terms, the strength of materials, the weight