alvanic fluid began to traverse (as
could be known by the effervescence of the acid, operating on the zinc
and copper) the cap of the camera was removed, and the plate exposed to
the sitter; at the same instant the point of the battery was brought
quickly against the back of the plate, and the cap replaced instantly.
If the plate is exposed more than an instant after the contact the
picture will generally be found solarized. By this process I have
taken pictures of persons in the act of walking, and in taking the
pictures of infants and young children I found it very useful.

Very respectfully yours,
THOMAS R. WHITNEY.

CHAP. VII

PAPER DAGUERREOTYPES.--ETCHING DAGUERREOTYPES.

Mr. Hunt describes a process, discovered by himself by which the
Daguerrean art may be applied to paper. His description is as
follows:--

"Placing the paper on some hard body, wash it over on one side--by
means of a very soft camel's hair pencil--with a solution of sixty
grains of bromide of potassium, in two fluid ounces of distilled water,
and then dry it quickly by the fire. Being dry, it is again washed
over with the same solution, and dried as before. A solution of
nitrate of silver--one hundred grains to an ounce of distilled
water--is to be applied over the same surface, and the paper quickly
dried in the dark. In this state the papers may be kept for use.

"When they are required, the above solution of silver is to be
plentifully applied, and the paper placed wet in the camera, the
greatest care being taken that no day light--not even the faintest
gleam--falls upon it until the moment when you are prepared, by
removing the dark slide, to permit the light, radiating from the object
you wish to copy, to act in producing the picture. After a few seconds
the light must be again shut off, and the camera removed into a dark
room." The necessity of removing the camera is now avoided by the use
of the dark slide, already described, covering the picture in the
holder, which alone may be removed.--Amer. Aut.

"It will be found by taking the paper from the holder, that there is
but a very faint outline--if any--yet visible. Place it aside, in
perfect darkness until quite dry; then place it in the mercurial vapor
box (meaning bath) and apply a very gentle heat to the bottom. The
moment the mercury vaporizes, the picture will begin to develope
itself. The spirit lamp must now be removed for a short time, and when
the acti