on of the mercury appears to cease, it is to be very carefully
applied again, until a well defined picture is visible. The
vaporization must then be suddenly stopped, and the photograph removed
from the box. The drawing will then be very beautiful and distinct;
but much detail is still clouded, for the developement of which it is
only necessary to place it in the dark and suffer it to remain
undisturbed for some hours. There is now an inexpressible charm about
the pictures, equaling the delicate beauty of the daguerreotype; but
being very susceptible of change, it must be viewed by the light of a
taper only. The nitrate of silver must now be removed from the paper,
by well washing it in soft water, to which a small quantity of salt has
been added, and it should afterwards be soaked in water only. When the
picture has been dried, wash it quickly over with a soft brush dipped
in a warm solution of hyposulphite of soda, and then wash it for some
time in distilled water, in order that all the hyposulphite may be
removed. The drawing is now fixed and we may use it to procure
positive copies, (the original being termed a negative,) many of which
may be taken from one original."

"The action of light on this preparation, does indeed appear to be
instantaneous. The exquisite delicacy of this preparation may be
imagined, when I state that in five seconds in the camera, I have,
during sunshine, obtained perfect pictures, and that when the sky is
overcast, one minute is quite sufficient to produce a most decided
effect."

"This very beautiful process is not without its difficulties; and the
author cannot promise that, even with the closest attention to the
above directions, annoying failures will not occur. It often happens
that some accidental circumstance--generally a projecting film or a
little dust--will occasion the mercurial vapor to act with great energy
on one part of the paper, and blacken it before the other portions are
at all effected. Again, the mercury will sometimes accumulate along
the lines made by the brush, and give a streaky appearance to the
picture, although these lines are not at all evident before the
mercurial vapor was applied. (A brush sufficiently large--and they may
be easily obtained--will, in a measure, prevent this difficulty.--Amer
Au.) I have stated that the paper should be placed wet in the camera;
the same paper may be used dry, which often is a great convenience.
When in the dry sta