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 white.  The correct observation of these tone values is a most important matter, and one of no little difficulty.

The word tone is used in two senses, in the first place when referring to the individual masses as to their relations in the scale of “tone values”; and secondly when referring to the musical relationship of these values to a oneness of tone idea governing the whole impression.  In very much the same way you might refer to a single note in music as a tone, and also to the tone of the whole orchestra.  The word values always refers to the relationship of the individual masses or tones in our imagined scale from black to white.  We say a picture is out of value or out of tone when some of the values are darker or lighter than our sense of harmony feels they should be, in the same way as we should say an instrument in an orchestra was out of tone or tune when it was higher or lower than our sense of harmony allowed.  Tone is so intimately associated with the colour of a picture that it is a little difficult to treat of it apart, and it is often used in a sense to include colour in speaking of the general tone.  We say it has a warm tone or a cold tone.

There is a particular rhythmic beauty about a well-ordered arrangement of tone values that is a very important part of pictorial design.  This music of tone has been present in art in a rudimentary way since the earliest time, but has recently received a much greater amount of attention, and much new light on the subject has been given by the impressionist movement and the study of the art of China and Japan, which is nearly always very beautiful in this respect.