taste. Grind the
white with the glycerine and a little water, mix to the gelatine dissolved
in the remainder of water, and filter through canvas. Apply the mixture
moderately hot, 30 deg. C. (86 deg. Fahr.)

_Transparencies.--_The transparencies are printed on a special tissue sold
under the name of "diapositive." It differs from the ordinary tissue in
this, that the mixture contains a greater quantity of the color matter,
India ink, which is ground exceedingly fine.

The proofs for transparencies should be printed deeper than those to be
seen by reflection, and developed on thin glass plates, free from any
defects, and coated with either one of the following substrata:

Soluble glass 5 parts
White of eggs 15 parts
Water 20 parts

The whole is beaten up to a thick froth and allowed to subside, when the
clear liquid is decanted, filtered through flannel and the glass plates
coated. The substratum should be allowed to dry for a few hours, and
rinsed under the tap before use.

The other substratum consists of

Gelatine 35 parts
Acetic acid, No. 8 250 parts
Alcohol, 95 deg 50 parts
Water 700 parts
Chrome alum, 4:100 60 parts

Dissolve the gelatine in the acid at a moderate heat, add afterwards the
alcohol and water, and lastly mix the chrome alum by small quantities at a
time.

These substrata are employed to avoid the peeling off of the image. To
prevent the entire desiccation of the gelatine, which is the cause of the
defect above alluded to, it is advisable to add glycerine to the washing
water after the image is cleared. Some operators recommend a coating of
flexible collodion, that is, prepared with castor oil, for the purpose in
question. We do not think that necessary when the transparencies are not
exposed to sunshine. If anything should be applied we would prefer the
encaustic.

Carbon transparencies are invaluable for reproducing negatives in the
original size by the same (carbon) process, or for enlarging by the
collodion or gelatine process. For these purposes they should be made on
the special red tissue manufactured by the Autotype Company, of London,
Eng. They can, however, be made on the ordinary tissues.

Whatever be the tissue employed, the transparencies for the reproduction
of negatives are seldom opaque enough, and should be intensified. This is
done by treating them with a very dilute solution of sodium permanganate,
which col