d tone may be had in nature herself, for though these
qualities have their scientific exposition, the divisions of the color
scale are not so easily comprehended by many people as the chart which may
be conceived in extended landscape. The sky, inasmuch as it spreads
itself over the earth and reflects its light upon it, dictates the _tone_
of the scene. The surface of the lake reveals this fact beyond dispute,
for the water takes on any tone which the sky may have. The sky's power
of reflection is no less potent in the landscape.

Reflection is observable in that degree in which the surface, reflected
upon, is rough or smooth. The absorbent surface allows the light to fall
in and disappear and under this condition we see the true or local color.
Note, for example, the effect of light on velvet or the hide of a cow in
winter. When the hair points toward the light the mass is rich and dark,
but when it turns away in any direction its polished surface reflects
light, which like the lake becomes a mirror to it.

Light falling upon a meadow will influence it by its own color only in
those places where the grass is turned at an angle from its rays.

From these few observations it becomes obvious that unity of tone is a
simple matter when understood by the painter and that unity, being a most
important part of his color scheme, may be increased by additions of
objects bearing the desirable color which nature fails to supply in any
particular subject. Thus if the day be one in which a warm mellow haze
pervades the air, those tones of the sky repeated upon the backs of
cattle, a roadway, clothing, or what not, may effect a more positive
tonality than the lesser items would give which also reflect it. Herein
then is the principle of Tonality: That all parts of the picture should be
bound together by the dominating color or colors of the picture.

With the indoor subject the consideration is equally strong. Let the
scheme be one as coloresque as the Venetian school took delight in, vivid
primaries in close juxtaposition (see small reproduction in _Fundamental
forms--The Cross_). The central figure, that of St. Peter is clothed in
dark blue with a yellow mantle. The Virgin's dress is deep red, her
mantle a blue, lighter than that of Peter's robe. Through the pillars is
seen the blue sky of still lighter degree. Thus the sky enters the
picture by graded approaches and focalizes upon the central figure. In
like manner