s recommended:--The paper should be moistened on the back
by sponging and blotting off. It should then be pinned on a board, the
moist side downwards, so that two of its edges (suppose the right-hand
and lower ones) shall project a little beyond those of the board. The
board then being inclined twenty or thirty degrees to the horizon, the
alcoholic tincture (mixed with a very little water, if the petals
themselves be not very juicy) is to be applied with a brush in strokes
from left to right, taking care not to go over the edges which rest on
the board; but to pass clearly over those that project; and observing
also to carry the tint from below upwards by quick sweeping strokes,
leaving no dry spaces between them, but keeping up a continuity of wet
spaces. When all is wet, cross them by another set of strokes from
above downwards, so managing the brush as to leave no floating liquid
on the paper. It must then be dried as quickly as possible over a
stove, or in a warm current of air, avoiding, however, such heat as may
injure the tint.

In addition to the flowers already mentioned in my third chapter, the
following are among those experimented upon and found to give tolerable
good photographic sensitives. I can only enumerate them, referring the
student, for any further information he may desire on the subject, to
Mr. Hunt's work; although what I have said above is sufficient for all
practical purposes; and any one, with the ambition, can readily
experiment upon them, without further research, on any other flower he
may choose.

Viola Odorata--or sweet sented violet, yields to alcohol a rich blue
color, which it imparts in high perfection to paper

Senecio Splendens--or double purple groundsel, yields a beautiful color
to paper.

The leaves of the laurel, common cabbage, and the grasses, are found
sufficiently sensitive.

Common Merrigold yields an invaluable faecula, which appears identical
with that produced by the Wall-flower, and Cochorus japonica mentioned
before, and is very sensitive, but photographs procured upon it cannot
be preserved, the color is so fugitive.

From an examination of the researches of Sir John Herschel on the
coloring matter of plants, it will be seen that the action of the sun's
rays is to destroy the color, effecting a sort of chromatic analysis,
in which two distinct elements of color are separated, by destroying
the one and leaving the other outstanding. The action is confined