captioned Figure
27.]

A vessel made of copper or brass, tinned inside, and large enough to
take in the largest plate, but not more than half an inch wide, is the
most convenient. It must be kept perfectly clean. Hot distilled water
is poured into it, and the temperature kept up by a spirit lamp.

Hyposulphite of Soda.--Having made a solution of hyposulphite of soda,
and well filtered it--the strength is immaterial; about half an ounce
of the salt to a pint of distilled water is sufficient--pour it into
one of the porcelain dishes, put into another plain, and into a third
distilled water. Immerse the plate with its face downwards into the
hyposulphite, and the whole of the sensitive is removed, and the light
has no farther action upon it; it is then to be removed from the
hyposulphite and plunged into the plain water, or placed upon the
support, fig. 25, and the water poured over it. It is then washed in a
similar manner with the distilled water and well examined, to see that
not the slightest particle of dust rests on the surface. The next step
is to dry it.

This may be readily accomplished by holding the plate with your plyers,
and pouring distilled water over it--if it is hot, so much the better.
Apply the spirit lamp to the back, at the corner held by the plyers, at
the same time facilitating the operation with the breath; pass the lamp
gradually downwards, finishing at the extreme corner. The last drop
may now be removed by a little bibulous paper. A single drop, even, of
distilled water allowed to dry on any part of the surface, is certain
to leave a stain which no after process can remove.

To illustrate the necessity for having perfectly clean water, and free
from all foreign matter--only to be avoided by using that which is
distilled--in these processes, I will relate a little anecdote.

An operator in this city (New York) frequently made complaint to me,
that his plates were occasionally very bad; coming out all over in
little black and white spots and spoiling many very good pictures,
regretting at the same time that perfect plates were not made, for he
had lost many customers in consequence of these defects. These
complaints being somewhat periodical, I suggested that the fault might
be in the hyposulphite, or chloride of gold solutions, or particles of
dust floating about in the room, and not in the plate.

A few days after he stated, that his plates having served him again in
the same way,