proceeding to, some given point, is perhaps, of all principles of
composition, the most influential in producing the beauty of groups of
form. Other laws make them forcible or interesting, but this generally
is chief in rendering them beautiful. In the arrangement of masses in
pictures, it is constantly obeyed by the great composers; but, like the
law of principality, with careful concealment of its imperativeness, the
point to which the lines of main curvature are directed being very often
far away out of the picture. Sometimes, however, a system of curves will
be employed definitely to exalt, by their concurrence, the value of some
leading object, and then the law becomes traceable enough.

In the instance before us, the principal object being, as we have seen,
the tower on the bridge, Turner has determined that his system of
curvature should have its origin in the top of this tower. The diagram
Fig. 34. page 369, compared with Fig. 32. page 361, will show how this
is done. One curve joins the two towers, and is continued by the back of
the figure sitting on the bank into the piece of bent timber. This is a
limiting curve of great importance, and Turner has drawn a considerable
part of it with the edge of the timber very carefully, and then led the
eye up to the sitting girl by some white spots and indications of a
ledge in the bank; then the passage to the tops of the towers cannot be
missed.

The next curve is begun and drawn carefully for half an inch of its
course by the rudder; it is then taken up by the basket and the heads of
the figures, and leads accurately to the tower angle. The gunwales of
both the boats begin the next two curves, which meet in the same point;
and all are centralised by the long reflection which continues the
vertical lines.

Subordinated to this first system of curves there is another, begun by
the small crossing bar of wood inserted in the angle behind the rudder;
continued by the bottom of the bank on which the figure sits,
interrupted forcibly beyond it,[255] but taken up again by the
water-line leading to the bridge foot, and passing on in delicate
shadows under the arches, not easily shown in so rude a diagram, towards
the other extremity of the bridge. This is a most important curve,
indicating that the force and sweep of the river have indeed been in old
times under the large arches; while the antiquity of the bridge is told
us by the long tongue of land, either of carted rubbis