in qualities of which no other word expresses, still exist, and
are probably as immortal as anything in this world can be. He should
know what those qualities are, and he should understand their relation
to the work of to-day.

Chiaroscuro is described by an old writer as suggesting "a theme which
is the most interesting, perhaps, in the whole range of the art of
painting. Of vast importance, great extent, and extreme intricacy.
Chiaroscuro is an Italian compound word whose two parts, _chiar_ and
_oscuro_, signify simply _bright_ and _obscure_, or _light_ and
_dark_. Hence the art or branch of art that bears the name regards
all the relations of light and shade, and this independently of
coloring, notwithstanding that in painting, coloring and the
clair-obscure are of their very nature inseparable. The art of
clair-obscure, therefore, teaches the painter the disposition and
arrangement in general of his lights and darks, with all their
degrees, extreme and intermediate, of tint and shade, both in single
objects, as the parts of a picture, and in combination as one whole,
so as to produce the best representation possible in the best manner
possible; that is, _so as to produce the most desirable effect upon
the senses and spirit of the observers_. In a word, its end and aim
are fidelity and beauty of imitation; its means, every effect of
light; chromatic harmonies and contrasts; chromatic values,
reflections; the degradations of atmospheric perspective, etc." The
italics are mine.

You see at once that this covers a pretty wide field. But it is to be
again noted that the use of chiaroscuro by the old painters meant not
only the expression of the light and shade of nature, but the so
arranging of the objects and the way that the light was permitted to
fall on them, that certain parts of the picture became shadow, while
the light was concentrated in some other part or parts. In this way
the arrangement of the light and shade of a picture became a distinct
element of composition, and a very important one. The _quality_ of
"light" was something to be emphasized by contrast. It is stated
(whether truly or not) that the proportion of light to dark was
according to a definite rule or principle with certain painters, some
permitting more, and some less, space of canvas to be proportioned to
light and to dark. The gradations of light and dark were studied of
course; but the quantity of light spread over the canvas was
calculate