nge and then coated with the
following solution, proceeding afterwards as in the cuprotype process:

Isinglass 8 parts
Uranic nitrate 5 parts
Copper nitrate 2 parts
Water 200 parts

_Printing on Opal, Celluloid, etc._, is quite simple; it suffices to coat
the material with the following gelatine solution, and, when the film is
dry, to proceed in operating by any one of the processes before described.

The sensitizing compound may be incorporated to the gelatine solution, but
we prefer not to do it and to sensitize the plates as they are wanted for
use.

A. Gelatine 4 parts
Water 70 parts in volume

Dissolve and mix little by little in order:

B. Chrome alum 0.25 parts
Water, hot 20 parts
C. Alcohol 10 parts

When coated place the plates on a level stand until the gelatine is set,
and let them dry on a rack.

_Transparencies._--Prepare the plate as directed above with

A. Gelatine 6 parts
Water 70 parts
B. Chrome alum 0.3 part
Water, hot 20 parts
C. Alcohol 10 parts

Sensitize with the uranic-copper solution employed in the cuprotype. By
this process transparencies of a rich brown, not actinic, color are
obtained. Consequently they can be used to reproduce negatives by the
same process. For lantern slides they may be toned black by platinic
chloride.

To strip off the picture, apply, first, on the glass plate a substratum of
India rubber, 2 to 100 of benzole, coat with plain collodion, immerse the
plate in water as soon as the film is set, and when greasiness has
disappeared pour on the gelatine solution and proceed.

For tranferring on any material, a sheet of paper is immersed in a
solution of India rubber cement in 20 parts of benzole, dried, coated with
the gelatine solution, sensitized, etc., by operating in the ordinary
manner. After development, the proof, being dry, is brushed over with
alumed gelatine moderately warm, dried, immersed in tepid water until the
gelatine is softened and tacky, when it is placed on the material and
squeezed into contact. This done, the transfer should be allowed to dry
thoroughly. Now, by imbuing the proof with benzole to dissolve the India
rubber, the paper is easily stripped off, leaving behind the picture
adhering to the material.

TRACING PROCESS ON METAL.

We call the attention of metal engravers to this process. It is well
known that wood engr