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 We now proceed with the details of the process as worked by Mr. Swan, adding a few foot-notes, giving our experience wherever it differs from that described so fully and so plainly by Mr. Simpson.

We shall endeavor to make plain the manipulations in the various stages of producing a carbon print.

The tissue is prepared by machinery, by which a perfect and uniform coating is secured. Each piece of paper is made into an endless band revolving round rollers, which keep it stretched, and repeatedly pass it over a surface of melted gelatine, sugar, and pigment, until a perfectly even coating of the right thickness is applied to the whole length. The trough of gelatine is kept at proper temperature by means of steam. By repeated contact with the gelatine, a thin coating being applied each time it passes over it, a much more perfect surface and even thickness of the gelatine is secured than could be obtained by any plan which applied the full thickness at once. By the arrangement adopted, waves of irregular draining are entirely avoided. These lengths of gelatine are then cut up to specific sizes, and will keep ad infinitum, ready for sensitizing when required.

It is important that the paper employed should possess a fine surface, and be quite free from inequalities and imperfections, in order that it may receive an even layer of the pigmented gelatine, as any imperfection in this layer may result in a blemish in the picture. It is also desirable that it (the paper) shall be sufficiently