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 which modify this. If, from over-exposure, the picture appear too dark, or from some tendency to insolubility in the compound, the image appear slowly, the temperature may be raised, when necessary, even to 150 degrees Fahrenheit; but high temperature must not be used until all the development has been effected that can be effected by water of a lower temperature.

The development is best commenced at as low a temperature as possible; and then, as soon as the image is fully made out, the print should be removed to cold water, in which the residue of bichromate will be washed away without risk of injury to the delicate half-tones, which would, with an under-exposed print, disappear in hot water. After two or three hours' immersion in cold water, the prints are one by one re-immersed in water at 80 or 90 degrees. Those which show signs of under-exposure are very carefully rinsed in merely tepid water, say 80 degrees, to clear away the soluble gelatine and adherent color; after which they are suspended to dry. The more fully-exposed prints remain longer in the warm water, in fact, until they become light enough. Any that are overexposed are put into hotter water, and are allowed to remain until the depth is sufficiently reduced. By judicious management of the development, using merely tepid water (not over 80 degrees), at the commencement of the operation, any under-exposed prints are discovered and saved. Then, by the use of hotter water to the more fully-exposed prints, these are speedily lightened to the required degree, and thus very few prints are lost either from under- or over-exposure.

When sufficient gelatine and coloring matter have been removed, and the prints are fully developed, they are hung up to dry. In the developing operation, several prints may be placed in one vessel; but as the image, although no longer soluble in water, is still slightly