re of
gelatine and bichromate of potash). The part of this thin, sensitive
film not exposed to the light is absorbent, and when immersed in water
swells up. The part exposed to the light, _i.e._, the lines of the
drawing, remains near the surface of the glass. Thus we have a sunk
mould from which a metal cast can be taken, leaving the lines in relief
as in the zinc process. In skilful hands this process admits of more
delicate gradations, and pale, uncertain lines can be reproduced with
tolerable fidelity. There is no process yet invented which gives better
results from a pen-and-ink drawing for the type press.

Reproductions of pencil, chalk, and charcoal are also possible by this
process; but _they are not suited for it_, and there is generally too
much working up by hand on the block to suit rapid printing. These
blocks when completed have a copper surface. The blocks take longer to
make, and are about double the price of the photo-zinc process. THE COST
varies from 9d. to 1/6 the square inch.

M. Gillot, in Paris, may be said to be the inventor or perfector of this
process, now used by many photo engravers in London, notably by Mr.
Alfred Dawson, of Hogarth Works, Chiswick.

HALF-TONE PROCESS.

FOR THE REPRODUCTION OF WASH DRAWINGS, PHOTOGRAPHS, ETC., BY THE
SCREENED PHOTO-ZINC RELIEF PROCESS.

This method of making the blocks is more complicated. As there are no
lines in a wash drawing, or in a photograph from nature, or in a
painting, it is necessary to obtain some kind of grain, or interstices
of white, on the zinc plate, as in a mezzotint; so between the drawing
or photograph to be reproduced and the camera, glass screens covered
with lines or dots, are interposed, varying in strength according to the
light and shade required; thus turning the image of the wash drawing or
photograph practically into "line," with sufficient interstices of white
for printing purposes.

The coarseness or fineness of grain on these blocks varies according to
circumstances. Thus, for rapid printing on cylinder machines, with
inferior paper and ink, a wider grain and a deeper cut block is
necessary.

The examples in this book may be said to show these process blocks at
their best, with good average printing. The results from wash drawings,
as already pointed out, are uncertain, and generally gloomy and
mechanical-looking.

The reproductions of pencil, chalk, or charcoal drawings by this process
are generally unsatisfactor