of
your conception. It is in the larger unity of your composition that the
imaginative faculty will be wanted, and variety in your forms should
always be subordinated to this idea.

Nature does not so readily suggest a scheme of unity, for the simple
reason that the first condition of your picture, the four bounding
lines, does not exist in nature. You may get infinite suggestions for
arrangements, and should always be on the look out for them, but your
imagination will have to relate them to the rigorous conditions of your
four bounding lines, and nature does not help you much here. But when
variety in the forms is wanted, she is pre-eminent, and it is never
advisable to waste inventive power where it is so unnecessary.

But although nature does not readily suggest a design fitting the
conditions of a panel her tendency is always towards unity of
arrangement. If you take a bunch of flowers or leaves and haphazard
stuff them into a vase of water, you will probably get a very chaotic
arrangement. But if you leave it for some time and let nature have a
chance you will find that the leaves and flowers have arranged
themselves much more harmoniously. And if you cut down one of a group of
trees, what a harsh discordant gap is usually left; but in time nature
will, by throwing a bough here and filling up a gap there, as far as
possible rectify matters and bring all into unity again. I am prepared
to be told this has nothing to do with beauty but is only the result of
nature's attempts to seek for light and air. But whatever be the
physical cause, the fact is the same, that nature's laws tend to
pictorial unity of arrangement.

[Sidenote: Variety of Tone Values]

It will be as well to try and explain what is meant by tone values. All
the masses or tones (for the terms are often used interchangeably) that
go to the making of a visual impression can be considered in relation to
an imagined scale from white, to represent the lightest, to black, to
represent the darkest tones. This scale of values does not refer to
light and shade only, but light and shade, colour, and the whole visual
impression are considered as one mosaic of masses of different degrees
of darkness or lightness. A dark object in strong light may be lighter
than a white object in shadow, or the reverse: it will depend on the
amount of reflected light. Colour only matters in so far as it affects
the position of the mass in this imagined scale of black and whit