: the first, the inimitable brilliancy of light in sky and in
sunlighted things; and the second, that among the tints which you can
imitate, those which you thought the darkest will continually turn out
to be in reality the lightest. Darkness of objects is estimated by us,
under ordinary circumstances, much more by knowledge than by sight;
thus, a cedar or Scotch fir, at 200 yards off, will be thought of darker
green than an elm or oak near us; because we know by experience that the
peculiar color they exhibit, at that distance, is the _sign_ of darkness
of foliage. But when we try them through the cardboard, the near oak
will be found, indeed, rather dark green, and the distant cedar,
perhaps, pale gray-purple. The quantity of purple and gray in Nature is,
by the way, another somewhat surprising subject of discovery.

166. Well, having ascertained thus your principal tints, you may proceed
to fill up your sketch; in doing which observe these following
particulars:

(1.) Many portions of your subject appeared through the aperture in the
paper brighter than the paper, as sky, sunlighted grass, etc. Leave
these portions, for the present, white; and proceed with the parts of
which you can match the tints.

(2.) As you tried your subject with the cardboard, you must have
observed how many changes of hue took place over small spaces. In
filling up your work, try to educate your eye to perceive these
differences of hue without the help of the cardboard, and lay them
deliberately, like a mosaic-worker, as separate colors, preparing each
carefully on your palette, and laying it as if it were a patch of
colored cloth, cut out, to be fitted neatly by its edge to the next
patch; so that the _fault_ of your work may be, not a slurred or misty
look, but a patched bed-cover look, as if it had all been cut out with
scissors. For instance, in drawing the trunk of a birch tree, there will
be probably white high lights, then a pale rosy gray round them on the
light side, then a (probably greenish) deeper gray on the dark side,
varied by reflected colors, and, over all, rich black strips of bark and
brown spots of moss. Lay first the rosy gray, leaving white for the high
lights _and for the spots of moss_, and not touching the dark side. Then
lay the gray for the dark side, fitting it well up to the rosy gray of
the light, leaving also in this darker gray the white paper in the
places for the black and brown moss; then prepare the moss