general tendency, but it is
modulated, as it proceeds, by myriads of subordinate curves. Thus the
outlines of a tree trunk are never as at _a_, Fig. 40, but as at _b_. So
also in waves, clouds, and all other nobly formed masses. Thus another
essential difference between good and bad drawing, or good and bad
sculpture, depends on the quantity and refinement of minor curvatures
carried, by good work, into the great lines. Strictly speaking, however,
this is not variation in large curves, but composition of large curves
out of small ones; it is an increase in the quantity of the beautiful
element, _but not a change in its nature_.

5. THE LAW OF RADIATION.

[Illustration: FIG. 40.]

We have hitherto been concerned only with the binding of our various
objects into beautiful lines or processions. The next point we have to
consider is, how we may unite these lines or processions themselves, so
as to make groups of _them_.

Now, there are two kinds of harmonies of lines. One in which, moving
more or less side by side, they variously, but evidently with consent,
retire from or approach each other, intersect or oppose each other:
currents of melody in music, for different voices, thus approach and
cross, fall and rise, in harmony; so the waves of the sea, as they
approach the shore, flow into one another or cross, but with a great
unity through all; and so various lines of composition often flow
harmoniously through and across each other in a picture. But the most
simple and perfect connexion of lines is by radiation; that is, by their
all springing from one point, or closing towards it: and this harmony is
often, in Nature almost always, united with the other; as the boughs of
trees, though they intersect and play amongst each other irregularly,
indicate by their general tendency their origin from one root. An
essential part of the beauty of all vegetable form is in this radiation:
it is seen most simply in a single flower or leaf, as in a convolvulus
bell, or chestnut leaf; but more beautifully in the complicated
arrangements of the large boughs and sprays. For a leaf is only a flat
piece of radiation; but the tree throws its branches on all sides, and
even in every profile view of it, which presents a radiation more or
less correspondent to that of its leaves, it is more beautiful, because
varied by the freedom of the separate branches. I believe it has been
ascertained that, in all trees, the angle at which, in their