lass crosswise in the centre; bend the ends
of the tin over the edge of the glass and turn them back so as to form
a groove to hold the glass, and still allow it to slide out and in.
These ends of the tin must be turned out flaring, that they may not
reflect in the glass.

Have a tin band about an inch wide made to fit close on the end of the
camera tube; place it on, and taking the tin containing the glass,
bring it to an angle of forty-five degrees with the tube, extending
nearly the whole length of the glass in front of the lenses; lap the
loose ends of the tin on each side of the tin rim, and having your
camera turned on the side to throw the view lengthwise, arrange the
exact angle by examining the image on the ground-glass. When you have
it exactly right, hold it while it is soldered fast to the band. Take
out your glass and stain the tin black, to prevent reflection.

CHEMICALS.

CHAPTER III.

Bromine and its Compounds--Iodine and its Compounds--Chlorine and its
compounds--Cyanide of Potassium--Hyposulphite of Soda--Hyposulphite of
Gold--Nitric Acid--Nitro-Muriatic Acid--Hydrochloric Acid--Hydrofluoric
Acid--Sulphuric Acid--Accelerating Substances--Liquid Sensitives--Dry
Sensitives, etc., etc.

BROMINE.

An article so extensively used in the practice of the Daguerreotypic
art as Bromine, is deserving of especial attention, and accordingly
every person should endeavor to make himself familiar with its
properties and applications.

History.--This element was discovered in 1826 by M. Balard, in the
mother-liquor, or residue of the evaporation of sea-water. It is named
from its offensive odor (bromos, bad odor). In nature it is found in
sea-water combined with alkaline bases, and in the waters of many
saline springs and inland seas. The salt springs of Ohio abound in the
compounds of bromine, and it is found in the waters of the Dead Sea.
The only use which has been made of bromine in the arts is in the
practice of photography. It is also used in medicine In a chemical
point of view it is very interesting, from its similarity in
properties, and the parallelism of its compounds to chlorine and iodine.

Dr. D. Alter, of Freeport, Pa., is the only American manufacturer, and
furnishes all of the "American Bromine." Yet we understand much
purporting to be of German manufacture is prepared from that made in
Freeport. This is done by individuals in this city, who get well paid
for the deception.