which to compose your tone symphonies. There
are no higher and lower octaves as in music to extend your effect. So be
very sparing with your tone values when modelling the different parts.

XIV

UNITY OF MASS

What has been said about unity of line applies obviously to the outlines
bounding the masses, so that we need not say anything further on that
subject. The particular quality of which something should be said, is
the unity that is given to a picture by means of a well-arranged and
rhythmically considered scheme of tone values.

The modifications in the relative tone values of objects seen under
different aspects of light and atmosphere are infinite and ever varying;
and this is quite a special study in itself. Nature is the great teacher
here, her tone arrangements always possessing unity. How kind to the eye
is her attempt to cover the ugliness of our great towns in an envelope
of atmosphere, giving the most wonderful tone symphonies; thus using
man's desecration of her air by smoke to cover up his other desecration
of her country-side, a manufacturing town. This study of values is a
distinguishing feature of modern art.

But schemes taken from nature are not the only harmonious ones. The
older masters were content with one or two well-tried arrangements of
tone in their pictures, which were often not at all true to natural
appearances but nevertheless harmonious. The chief instance of this is
the low-toned sky. The painting of flesh higher in tone than the sky was
almost universal at many periods of art, and in portraits is still
often seen. Yet it is only in strong sunlight that this is ever so in
nature, as you can easily see by holding your hand up against a sky
background. The possible exception to this rule is a dark storm-cloud,
in which case your hand would have to be strongly lit by some bright
light in another part of the sky to appear light against it.

This high tone of the sky is a considerable difficulty when one wishes
the interest centred on the figures. The eye instinctively goes to the
light masses in a picture, and if these masses are sky, the figures lose
some importance. The fashion of lowering its tone has much to be said
for it on the score of the added interest it gives to the figures. But
it is apt to bring a heavy stuffy look into the atmosphere, and is only
really admissible in frankly conventional treatment, in which one has
not been led to expect implicit truth to natura