iodide,
potassium, &c.--the same water never being used for two different
operations.

White Bibulous Paper.

Photogenic Camera--Fig. 9.

Pressure Frame--Fig 29.

Paper, of the very best quality--directions for the choice of which
have been already given.

A Screen of Yellow Glass.

Camels' or Badgers' hair Brushes:--A seperate one being kept for each
wash and solution, and which should be thoroughly cleansed immediately
after using in distilled water. That used for the gallo-nitrate is
soon destroyed, owing to the rapid decomposition of that preparation.

A Graduated Measure.

Three or Four Flat Boards, to which the paper may be fixed with drawing
pins.

A Hot Water Drying Apparatus, for drying the paper will also be found
useful.

In preparing the Calotype paper, it is necessary to be extremely
careful, not only to prevent the daylight from impringing upon it, but
also to exclude, if possible, the strong glare of the candle or lamp.
This may be effected by using a shade of yellow glass or gauze, which
must be placed around the light. Light passing through such a medium
will scarcely affect the sensitive compounds, the yellow glass
intercepting the chemical rays.

Preparation of the Iodized Paper.--Dissolve one hundred grains of
crystalized nitrate of silver in six ounces of distilled water, and
having fixed the paper to one of the boards, brush it over with a soft
brush on one side only with this solution, a mark being placed on that
side whereby it may be known. When nearly dry dip it into a solution
of iodide of potassium, containing five hundred grains of that salt
dissolved in a pint of water. When perfectly saturated with this
solution, it should be washed in distilled water, drained and allowed
to dry. This is the first part of the process, and the paper so
prepared is called iodized paper. It should be kept in a port-folio or
drawer until required: with this care it may be preserved for any
length of time without spoiling or undergoing any change.

Mr. Cundell finds a stronger solution of nitrate of silver preferable,
and employs thirty grains to the ounce of distilled water: he also adds
fifty grains of common salt to the iodide of potassium, which he
applies to the marked side of the paper only. This is the first
process.

Preparation of the paper for the Camera.--The second process consists
in applying to the above a solution which has been named by Mr. Talbot
the "Gallo-Nitrate o