vertical line of the screen at the back, while the whole swing hangs on
the diagonal from top left-hand corner to right; lower corner, to which
the strongly marked edge of the bed-clothes and pillow at the bottom of
the picture is parallel.

[Illustration: Plate XLV.

CORREGGIO. VENUS. MERCURY, AND CUPID (NATIONAL GALLERY)

A fine example of one of the most effective tone arrangements; a
brilliantly-lit, richly-modelled light mass on a dark background.

_Photo Hanfstaengl_]

Large flat tones give a power and simplicity to a design, and a
largeness and breadth of expression that are very valuable, besides
showing up every little variety in the values used for your modelling;
and thus enabling you to model with the least expenditure of tones.
Whatever richness of variation you may ultimately desire to add to your
values, see to it that in planning your picture you get a good basic
structure of simply designed, and as far as possible flat, tones.

In speaking of variety in mass we saw how the #nearer these tones are in
the scale of values, the more reserved and quiet the impression
created#, and the #further apart or greater the contrast, the more
dramatic and intense the effect#. And the sentiment of tone in a
picture, like the sentiment of line and colour, should be in harmony
with the nature of your subject.

Generally speaking #more variety of tone and shape in the masses of
your composition is permissible when a smaller range of values is used
than when your subject demands strong contrasts#. When strong contrasts
of tone or what are called black and white effects are desired, the
masses must be very simply designed. Were this not so, and were the
composition patterned all over with smaller masses in strong contrast,
the breadth and unity of the effect would be lost. While when the
difference of relative values between one tone and another is slight,
the oneness of effect is not so much interfered with by there being a
large number of them. Effects of strong contrasts are therefore far the
most difficult to manage, as it is not easy to reduce a composition of
any complexity to a simple expressive pattern of large masses.

This principle applies also in the matter of colour. Greater contrasts
and variety of colour may be indulged in where the middle range only of
tones is used, and where there is little tone contrast, than where there
is great contrast. In other words, you cannot with much hope of success
hav