itizers which
had already been suggested, in order to learn which was the best, and
then, if possible, _why_ it was the best, as a guide to further research.
Chlorophyl was the only thing I tried which was sufficiently sensitive to
red to offer any encouragement in that direction; but the solution which
I obtained was weak and unstable, and far from being a satisfactory color
sensitizer. Hoping to obtain a better solution with which to continue my
experiments, I made extracts from many kinds of leaves, and found that a
solution from blue myrtle leaves looked better and kept better than any
other, and when it was applied to the silver-bromide plates they became
remarkably sensitive, not only to all shades of red, but also to orange,
yellow, and green. By placing in front of the lens a color-screen
consisting of a small glass tank containing a weak solution of bichromate
of potash, to cut off part of the blue and violet light, I obtained, with
these chlorophyl plates, the first photographs in which all colors were
reproduced in the true proportions of their brightness. But my chief
desire at that time was to realize a method of producing from any object
in colors a set of three negatives, in one of which the shadows should
represent the blue of the original, in another the yellow, and in another
the red, in such a manner that transparent pigment prints from these
negatives--blue, yellow, and red--would, when superimposed on a white
surface, represent not only the lights and shadows, but also the colors
of the object. This had already been attempted by others, who failed
because their plates were not sufficiently sensitive to red and yellow.

Having succeeded perfectly in my undertakings, I published my discovery
in 1879,[1] explaining how to prepare and use the chlorophyl plates, in
connection with the yellow screen, for the purpose of securing correct
photographs of colored objects.[2]

[Footnote 1: _Philadelphia Photographer_, December, 1879, p. 365.]

[Footnote 2: I intended this publication to be a very full and explicit
one, and it was sufficiently so to be perfectly understood by most who
saw it; but some may think I did not sufficiently emphasize the
importance of using the particular kind of chlorophyl which I mentioned.
In a brief communication to the editor of the _Photo. News_, in 1883, I
described some experiments with eosine as a color sensitizer, and then
called attention to the superiority of blue-myrtle c