Ruskin, John: The elements of drawing: in three letters to beginners (London, 1857)

letter in.] ON COLOUK AND COMPOSITION.

269

4. THE LAW OF CUKVATUKE.

There is, however, another point to be noticed
in this bridge of Turner's. Not only does it slope
away unequally at its sides, but it slopes in a
gradual though very subtle curve. And if you
substitute a straight line for this curve (drawing
one with a rule from the base of the tower on each
side to the ends of the bridge, in Fig. 34., and
effacing the curve,) you will instantly see that the
design has suffered grievously. You may ascertain,
by experiment, that all beautiful objects whatsoever
are thus terminated by delicately curved lines, ex-
cept where the straight line is indispensable to
their use or stability; and that when a complete
system of straight lines, throughout the form, is
necessary to that stability, as in crystals, the beauty,
if any exists, is in colour and transparency, not in
form. Cut out the shape of any crystal you like,
in white wax or wood, and put it beside a white
lily, and you will feel the force of the curvature