g of gelatine, and dissolves the not acted on gelatine in warm
water, a very fine positive image is obtained by means of acidified inks
which will fix themselves on the bare paper.

Positive impressions from positive cliches can also be obtained in
operating in the following manner: On its removal from the printing frame
the proof is washed, sponged between sheets of blotting paper, then
covered with not acidified India ink mixed with potassium bichromate, and,
when dry, exposed from the verso to the action of light. This done the
image is cleared with a somewhat hard brush.

THE CARBON PROCESS.

The carbon tissue is seldom prepared by photographers. However, for the
sake of completeness, we shall give the formula of the mixtures most
generally employed, and describe the manner of coating the paper on a
small scale.

_Preparation of the Tissue.--_The gelatine generally recommended to
compound the mixture is the Nelson's autotype gelatine. Coignet's gold
label gelatine, mixed with a more soluble product, such as Cox's gelatine,
for example, gives also excellent results.

Gelatine 110 parts
Sugar 25 parts
Soap, dry 12 parts
Water 350 parts

The coloring substances consist of:

FOR ENGRAVING BLACK.
Lamp-black 20 parts
Crimson lake 2 parts
Indigo 1 part

FOR WARM BLACK.
Lamp-black 3 parts
Crimson lake 3 parts
Burnt amber 2 parts
Indigo 1 part

FOR SEPIA
Lamp-black 2 parts
Sepia of Cologne 18 parts

FOR PHOTOGRAPHIC RED BROWN.
India ink 3 parts
Crimson lake 4 parts
Van Dyck brown 4 parts

For blue, Turnbull's blue is employed; for yellow, light chrome yellow;
for red, carmine dissolved in aqueous ammonia, evaporating, then adding
water, etc. (See further on.)

To prepare the mixture, dissolve the sugar and soap in the cold water, add
the gelatine, let it soak for an hour, then dissolve it in a water bath
and mix by small quantity the colors finely ground together and wetted to
the consistency of a paste. After filtering through flannel the mixture
is ready for use.

For coating, the method devised by Mr. Alf. Harman has been found
excellent in the hands of the writer, not only for the purpose in
question, but also for coating paper with gelatinous or viscous (gum
arabic) preparations.

"Take two tin dishes, such as used for the development of the carbon
prints; arrange one on your bench tilted to an an