any, more sensitive than this. We frequently work it with the
ordinary coating in twelve and fifteen seconds. The manner in which
the sensitives are worked is by coating very light. In this way, a
flat, shallow picture is obtained in a few seconds; and the same can be
done with any of the more volatile quicks.

It is a fact not generally known, that a plate coated in a light
chemical room is more sensitive than when coated in darkness. By
admitting a free, uniform light, and exposing the plate to it a few
seconds after coating, then timing short in the camera, a very light,
clear impression is obtained. The time in the camera is reduced in
proportion to the previous action of light. The shades, of course, are
destroyed, and the tone injured; still, for taking children, we have
succeeded better by this method than by the use of "sensitives." The
discovery of this principle was accidental, while operating where the
direct ray s of the sun, entering the window just before sunset, fell
on the curtain of our dark room, rendering it very light within.

The selection of iodine is not unimportant. Reject, at once, that
which has anything like a dull, black, greasy appearance; and select
that which is in beautiful large crystalline scales, of a purple color,
and brilliant steel lustre.

Solarization, and general blueness of all the light parts of the
picture, were formerly great obstacles to success, though now scarcely
thought of by first-class artists. Beginners in the art, however, are
still apt to meet with this difficulty. It is occasioned by dampness
in the iodine box, which causes the plate to become coated with a
hydro-iodide of silver, instead of the iodide. The remedy is in drying
your iodine. If in summer, you can open your box and set it in
sunshine a few minutes; or if in winter, set it under a stove a short
time. The true method, however, is to dry it by means of the chloride
of calcium. It has such a remarkable affinity for water, that a small
fragment placed in the open air, even in the dryest weather, soon
becomes dissolved.

Take one or two ounces of this chemical, heat it in the drying bath, or
in a hot stove, to perfect dryness; place it in a small glass toy dish,
or large watch crystal, and set it in the centre of your iodine box.
Take this out and heat to dryness every morning. Adopt this process,
and with your mercury at a high temperature, you will never be troubled
with blue pictures.