f grandeur dwarfing into
insignificance the aurora borealis in its most resplendent moments.

XXIII

THE EXPRESSIVENESS OF LIGHT

From an esthetic or, more broadly, a psychological point of view no
medium rivals light in expressiveness. Not only is light allied with
man's most important sense but throughout long ages of associations and
uses mankind has bestowed upon it many attributes. In fact, it is
possible that light, color, and darkness possess certain fundamentally
innate powers; at least, they have acquired expressive and impressive
powers through the many associations in mythology, religion, nature, and
common usage. Besides these attributes, light possesses a great
advantage over the media of decoration in obtaining brightness and color
effects. For example, the landscape artist cannot reproduce the range of
values or brightnesses in most of nature's scenes, for if black is used
to represent a deep shadow, white is not bright enough to represent the
value of the sky. In fact, the range of brightnesses represented by the
deep shadow and the sky extends far beyond the range represented by
black and white pigments. The extreme contrast ordinarily available by
means of artist's colors is about thirty to one, but the sky is a
thousand times brighter than a shadow, a sunlit cloud is thousands of
times brighter than the deep shadows of woods, and the sun is millions
of times brighter than the shadows in a landscape.

The range of brightnesses obtainable by means of light extends from
darkness or black throughout the range represented by pigments under
equal illumination and beyond these through the enormous range
obtainable by unequal illumination of surfaces to the brightnesses of
the light-sources themselves. In the matter of purity of colors, light
surpasses reflecting media, for it is easy to obtain approximately pure
hues by means of light and to obtain pure spectral hues by resorting to
the spectrum of light. It is impossible to obtain pure hues by means of
pigments or of other reflecting media. These advantages of light are
very evident on turning to spectacular lighting effects, and even the
lighting of interiors illustrates a potentiality in light superior to
other media. For example, in a modern interior in which concealed
lighting produces brilliantly illuminated areas above a cornice and dark
shadows on the under side, the range in values is often much greater
than that represented by black and