convinced of the
practicability of producing beautiful solar pictures in this way; but,
alas! my picture vanished and with it, all--no not all--my hopes. With
renewed determination I began again by studying the nature of the
preparation, and came to the conclusion, that if I could destroy the
part not acted upon by the light without injuring that which was so
acted upon, I could save my pictures. I then made a strong solution of
sal. soda I had in the house, and soaked my paper in it, and then
washed it off in hot water, which perfectly fixed the view upon the
paper. This paper was very poor with thick spots, more absorbent than
other parts, and consequently made dark shades in the picture where
they should not have been; but it was enough to convince me that I had
succeeded, and that at some future time, when I had the means and a
more extensive knowledge of chemistry, I could apply myself to it
again. I have done so since, at various times, with perfect success;
but in every instance laboring under adverse circumstances."

I have very recently learned, that, under the present patent laws of
the United States, every foreign patentee is required to put his
invention, or discovery, into practical use within eighteen months
after taking out his papers, or otherwise forfeit his patent. With
regard to Mr. Talbot's Calotype patent, this time has nearly, if not
quite expired, and my countrymen are now at perfect liberty to
appropriate the art if they feel disposed. From the statement of Mr.
Wattles, it will be perceived that this can be done without dishonor,
as in the first instance Mr. Talbot had no positive right to his patent.

Photography; or sun-painting is divided, according to the methods
adopted for producing pictures, into

DAGUERREOTYPE, CHROMATYPE,
CALOTYPE, ENERGIATYPE,
CHRYSOTYPE, ANTHOTYPE and
CYANOTYPE, AMPHITYPE.

CHAP. II.

THE THEORY ON LIGHT.--THE PHOTOGRAPHIC PRINCIPLE

Some philosophers contend that to the existence of light alone we owe
the beautiful effects produced by the Photogenic art, while others give
sufficient reasons for doubting the correctness of the assumption.
That the results are effected by a principle associated with light and
not by the luminous principle itself, is the most probable conclusion.
The importance of a knowledge of this fact becomes most essential in
practice, as will presently be seen. To this principle Mr. Hunt gives
the name of E