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 but very heavy pressure is indispensable. We find any ordinary bed-plate press, with the plate moving between the rollers, to be applicable to this stage of the process. The plate should be entirely level. In rolling, the India-rubber coated paper is laid on the steel plate, and a blanket of thick felt is laid over the tissue, which is uppermost, whilst it passes through the press.

We may remark here, that whilst the prepared surface of the sensitive tissue must be always carefully shielded from light, when once that has been covered up by mounting, it may be submitted to a dull, diffused light with impunity, care being taken that the back of the original tissue, which has now been rendered very non-actinic by the yellow color of the bichromate with which it is saturated, be uppermost. This permits the rolling of the mounted tissue to be effected in a moderately light room. The back of each print should be examined, and any India-rubber solution removed by rubbing with a piece of India-rubber. The object of this precaution is to secure uniform development. If some portions were rendered waterproof by patches of India-rubber at the back, such spots would be protected from the action of the water for a time, and would be incompletely developed when the other portions of the print were finished; the result of which would be a patch of a deeper tint than the remainder of the picture.

The print is now ready for development. To effect this, a plentiful supply of warm water is necessary. In the Newcastle establishment, a series of three large wood-troughs are used. These are provided with hot and cold water-taps and waste-pipe. Into these troughs the prints are passed in succession. This ready supply of water