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 again turned, and is drawn repeatedly through the solution. It then has clothes-clips attached along one of the edges, and is slowly withdrawn, so that the solution drains off without being repelled from the face of the tissue, and running off in streams. If the sheet is large, a thin lath of wood may be laid along the edge of the tissue that is first withdrawn from the trough, the tissue and lath being clipped together with clothes-clips. The time of immersion may vary from one to three minutes, depending somewhat on temperature and on the facility with which the tissue absorbs the solution. As a rule, as soon as it is quite limp from the thorough permeation of the solution, it should be removed. The longer the immersion, within certain limits, the more sensitive will be the tissue; but if too much prolonged, there is danger of two serious evils. In the first place, the paper becomes rotten, the gelatine also loses toughness, and the large quantity of water absorbed renders it liable to tear with its own weight. In the next place, long immersion in a saturated solution is apt to produce a crystallized surface in drying, which, of course, renders the tissue quite useless. As a rule, perhaps, two minutes will be about the average time of immersion; but a knowledge of the degree of pliancy required will be gained from two or three experiments.

The tissue should be placed to dry in a dark room, through which a current of dry air is constantly passing. In the first stage of drying, the temperature, of the air must not be above 60 or 70 degrees Fahr., for otherwise the gelatine, already softened with water, would melt. During damp weather, the air of the drying-room may be raised 10 degrees after the tissue has become half dry. If the drying be slow, the development of the image afterwards will be extremely slow or altogether