d more transparent, and its lights become
whiter. It is also rendered exceedingly permanent. After this process
the picture may be waxed, and thus its transparency increased. This
process is applicable to all photographic papers prepared with
solutions of silver.

Having thus fully, and it is hoped clearly, considered the process, it
may be necessary before dismissing the calotype from notice, to add one
or two remarks from the observations and labors of some who have
experimented in this art. Dr. Ryan in his lectures before the Royal
Polytechnic Institution, has observed, that in the iodizing process the
sensitiveness of the paper is materially injured by keeping it too long
in the solution of iodide of potassium, owing to the newly formed
iodide of silver being so exceedingly solvable in excess of iodide of
potassium as in a few minutes to be completely removed. The paper
should be dipped in the solution and instantly removed. There is
another point, too, in the preparation of the iodized paper in which
suggestions for a slight deviation from Mr. Talbot's plan have been
made. In the first instance, it is recommended that the paper be
brushed over with the iodide of potassium, instead of the nitrate of
silver, transposing, in fact, the application of the first two
solutions. The paper, having been brushed over with the iodide of
potassium in solution, is washed in distilled water and dried. It is
then brushed over with nitrate of silver, and after drying is dipped
for, a moment in a fresh solution of iodide of potassium of only
one-fourth the strength of the first, that is to say, one hundred and
twenty-five grains of the salt to a pint of water. After this it is
again washed and dried. The advantage derived from this method, is a
more sensitive paper, and a more even distribution of the compounds
over the surface.

Another deviation from Mr. Talbot's method has been suggested, as
follows:

Brush the paper over with a solution of one hundred grains of nitrate
of silver to an ounce of water. When nearly, but not quite, dry, dip
it into a solution of twenty-five grains of iodide of potassium to one
ounce of distilled water, drain it, wash it in distilled water and
again drain it. Now brush it over with aceto-nitrate of silver, made
by dissolving fifty grains of nitrate of silver in one ounce of
distilled water, to which is added one sixth of its volume of strong
acetic acid. Dry it with bibulous paper,