ure may thus be built up by successive additions and
alterations, not all put upon one surface, but constituting a number
of "monochromes," superimposed one upon the other. When finished, each
of these one-colour transparencies can then be reproduced by
photo-mechanical means for multi-colour printing in the press.

By what are known as the photographic "interruption" processes, a kind
of converse method has achieved a certain degree of success. A
landscape or a picture is photographed several times from exactly the
same position, but on each occasion it is taken through a screen of a
different coloured glass, which is intended for the purpose of
intercepting all the rays of light, except those of one particular
tint. Coloured prints in transparent gelatine or other suitable medium
are then made from the various negatives, each in its appropriate
tint; and when all are placed together and viewed through transmitted
light, the effect of the picture, with all its colours combined, is
fairly well produced. More serviceable from the artistic point of view
will be the method according to which the artist makes his picture by
transmitted light, but the finished printed product is seen on paper,
because this latter lends itself to the finest work of the artistic
printer.

The principal branch of the work of the photographer must continue to
be portraiture. He cannot greatly reduce the cost of getting a really
good negative, because so much hand-labour is required for the task of
"retouching"; but he can give, perhaps, a hundred prints for the price
which he now charges for a dozen, and make money by the enterprise. It
has already been proved that there is no necessity for using expensive
salts of gold, silver or platinum in order to secure the most artistic
prints; and, as a matter of fact, some of the finest art work in the
photography of the past quarter of a century has been accomplished
with the cheapest of materials, such as gelatine, glue and lampblack.

Pigmented gelatine is, without doubt, the coming medium for
photographic prints, and the methods of making them must approximate
more and more closely to those of the typographic printer. By
producing a "photo-relief" in gelatine--sensitised with bichromate of
potash, and afterwards exposed first to the sun and then to the action
of water--an impression in plastic material can be secured, from
which, with the use of warm, thin, pigmented gelatine, a hundred
copies or