carefully and completely dried, as
this is essential to its proper preparation. It is then dipped into a
solution of nitrate of silver, and dried without artificial heat in a
room from which every ray of light is carefully excluded. By this
process it acquires a very remarkable facility in being blackened on a
very slight exposure to light, even when the latter is by no means
intense. The paper, however, rapidly loses its extreme sensitiveness
to light, and finally becomes no more impressionable by the solar beams
than common nitrate paper.

Bromide Paper.--Of all common photographic paper, the best, because the
least troublesome in making, and the most satisfactory in result, is
that which is termed bromine paper, and which is thus
prepared:--Dissolve one hundred grains of bromide of potassium in one
ounce of distilled water, and soak the paper in this solution. Take
off the superfluous moisture, by means of your bibulous paper, and when
nearly dry, brush it over on one side only, with a solution of one
hundred grains of nitrate of silver to an ounce of distilled water.
The paper should then be dried in a dark room, and, if required to be
very sensitive, should a second time be brushed over with the nitrate
of silver solution.

In preparing the papers mentioned above, there are two circumstances
which require particular attention. In the first place, it is
necessary to mark the paper on the side spread with the solutions of
nitrate of silver, near one of the extreme corners. This answers two
purposes: in the first place it serves to inform the experimentalist
of the sensitive surface; and secondly, it will be a guide as to which
portion of the papers has been handled during the application of the
solution, as the impress of the fingers will probably come out upon the
photograph. The second caution is, that the application of the
sensitive solution (nitrate of silver,) and the subsequent drying of
the paper, must be always conducted in a perfectly dark room, the light
of a candle alone being used.

[Illustration: Fig. 29 (hipho_29.gif)]

III. PHOTOGENIC PROCESS ON PAPER.--Method.--The simplest mode is to
procure a flat board and a square of glass, larger in size than the
object intended to be copied. On the board place the photographic
paper with the prepared side upwards, and upon it the object to be
copied; over both lay the glass and secure them so that they are in
close connection by means of binding