paper bearing its delicate gelatine print is pulled off and dried.

LINE REPRODUCTION FROM PEN AND INK.

(Original 14 x 11 inches.)LINE REPRODUCTION FROM PEN AND INK.

Beautiful as many of these are, they can only be applied where the expense attending them and the slower printing is not an objection, and where letterpress is not required on the same sheet at the same printing. Printing matter can of course be afterwards introduced, but this must be by a second operation.

We have now left for consideration the relief processes, in which the design to be printed is produced similar in character and appearance to that of the movable letterpress type used by printers.

FEEDING THE CHICKENS.

(Half-tone from photogram. Original 14 x 11 inches.)

These processes are roughly divisible into two sections, "tone" and "line," to understand which I will refer the reader to the accompanying illustrations.

In these the image appears to be respectively composed of lines of varying strength and proximity in the one, and of tints ranging from grey to black in the other. If the latter be closely examined, however, or looked at through a magnifying glass, it will be found that what at first appears to be a flat even tint is composed of an infinite number of dots arranged in a reticulated or geometrical pattern. We will now see how this effect is produced, and what are the especial uses of this so-called "tone" or "half-tone" process.

THE HERON HOUSE.

Half-tone from photogram. (Original 14 x 11 inches.)

Half-Tone Process.

As has been already said, it is of course necessary to produce from the original a printing surface of such a kind as shall take ink and print an image therefrom. Now it will of course be obvious that with ink and white paper we can only produce two things—black and white—and that therefore all the intermediate shades must be produced by a greater or less number of black dots. The process under consideration, in common with some others, is based upon the fact that gelatine or albumen sensitised with bichromate of ammonium or potassium, becomes insoluble after being acted upon by light. A solution of bitumen in benzole also forms a light sensitive coating which is frequently used in these processes. If we were to expose such a sensitive film to light under (for example) a photographic negative of a figure taken against a light background and then washed it in a suitable solvent, those parts which had been protected from light by the opaque portions of the negative, such as the background, the face, hands, and white portions of the dress, would dissolve away, leaving the insoluble or light affected portions standing.