PROPOSITIONS.


PROPOSITION 19.
The above supposes the colours to be used in
their prismatic intensities, but each colour has
a variety of tones when mixed with white, or
of shades when mixed with grey or black.
When a full colour is contrasted with
another of a lower tone, the volume of
the latter must be proportionally in-
creased.
PROPOSITION 20.
Each colour has a variety of hues, obtained by
admixture with other colours, in addition to
white, grey, or black: thus we have of yellow,
-orange-yellow on the one side, and lemon-
yellow on the other; so of red,-scarlet-red,
and crimson-red; and of each every variety of
tone and shade.
When a primary tinged with another
primary is contrasted with a secondary,
the secondary must have a hue of the
third primary.


PROPOSITION 21.
In using the primary colours on
moulded surfaces, we should place blue,
which retires, on the concave surfaces;
yellow, which advances, on the convex;
and red, the intermediate colour, on the
undersides; separating the colours by
white on the vertical planes.
When the proportions required by Proposition 18
cannot be obtained, we may procure the balance
by a change in the colours themselves: thus,
if the surfaces to be coloured should give too
much yellow, we should make the red more
crimson and the blue more purple,-i.e. we
should take the yellow out of them; so if the
surfaces should give too much blue, we should
make the yellow more orange and the red more
scarlet.
PROPOSITION 22.
The various colours should be so
blended that the objects coloured, when
viewed at a distance, should present a
neutralised bloom.


PROPOSMowN 23.
No composition can ever be perfect
in which any one of the three primary
colours is wanting, either in its natural
state or in combination.
PROPOSIToNo 24.
When two tones of the same colour On the law of
simultaneous
are juxtaposed, the light colour will contrasts of
olours, de-
appear lighter, and   the dark colour rived from
1                          ~~~~~~~~~~~~~Mons. Chev-
darrer.                                ruil.
PROPOSITION 25.
When two different colours are juxta-
posed, they receive a double modification;
first, as to their tone (the light colour
appearing lighter, and the dark colour
appearing darker); secondly, as to their
hue, each will become tinged with the
complementary colour of the other.


PROPOSIT ION 26.


Colours on white grounds appear
darker; on black grounds lighter.
PROPOSITION 27.
Black grounds suffer when opposed
to colours which give a luminous com-
pletnentary.
PROPOSITION 28.
Colours should never be allowed to
impinge upon each other.
PROPOSITION 29.


When ornaments in a colour are on a
ground of a contrasting colour, the orna-
ment should be separatedfrom the ground
by an edging of lighter colour; as a red
flower on a green ground should have an
edging of lighter red.
7


On the means
of increasing
the harmo-
nious effects
of juxtaposed
colours.
Observations
derived from
a considera-
tion of
Oriental
practice.


On the con-
trasts and
harmonious
equivalents
of tones,
shades, and
hues.


On the posi-
tions the se-
veral colours
should oc-
cupy.