parts of a picture, so as to bring all in harmony with that oneness of impression that should dominate the whole; how much of your scale of values it is permissible to use for the modelling of each individual part.  In the best work the greatest economy is exercised in this respect, so that as much power may be kept in reserve as possible.  You have only the one scale from black to white to work with, only one octave within the limits of 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 natural effect.  If truth to natural appearances is carried far in the figures, the same truth will be expected in the background; but if only certain truths are selected in the figures, and the treatment does not approach the naturalistic, much more liberty can be taken with the background without loss of verisimilitude.