sign and stimulus of the most furious and fatal
passions that have rent the nations: blue against green, in the decline
of the Roman Empire; black against white, in that of Florence; red
against white, in the wars of the Royal houses in England; and at this
moment, red against white, in the contest of anarchy and loyalty, in all
the world.

14. On the other hand, the directly ethical influence of colour in the
sky, the trees, flowers, and coloured creatures round us, and in our own
various arts massed under the one name of painting, is so essential and
constant that we cease to recognize it, because we are never long enough
altogether deprived of it to feel our need; and the mental diseases
induced by the influence of corrupt colour are as little suspected, or
traced to their true source, as the bodily weaknesses resulting from
atmospheric miasmata.

15. The second musical science which belongs peculiarly to sculpture
(and to painting, so far as it represents form), consists in the
disposition of beautiful masses. That is to say, beautiful surfaces
limited by beautiful lines. Beautiful _surfaces_, observe; and remember
what is noted in my fourth lecture of the difference between a space and
a mass. If you have at any time examined carefully, or practised from,
the drawings of shells placed in your copying series, you cannot but
have felt the difference in the grace between the aspects of the same
line, when enclosing a rounded or unrounded space. The exact science of
sculpture is that of the relations between outline and the solid form it
limits; and it does not matter whether that relation be indicated by
drawing or carving, so long as the expression of solid form is the
mental purpose; it is the science always of the beauty of relation in
three dimensions. To take the simplest possible line of continuous
limit--the circle: the flat disc enclosed by it may indeed be made an
element of decoration, though a very meagre one but its relative mass,
the ball, being gradated in three dimensions, is always delightful.
Here[110] is at once the simplest, and in mere patient mechanism, the
most skilful, piece of sculpture I can possibly show you,--a piece of
the purest rock-crystal, chiselled, (I believe, by mere toil of hand,)
into a perfect sphere. Imitating nothing, constructing nothing;
sculpture for sculpture's sake, of purest natural substance into
simplest primary form.

16. Again. Out of the nacre of any mussel or oyst