number, and of unimpeachable quality, a thing commercially practicable.
There are two modes of proceeding in forming the tissue, either of which may be adopted, as circumstances may render desirable. The first consists in coating a plate of glass with plain collodion, and upon this film applying a mixture of gelatine, sugar, coloring matter, and bichromate of potash. When this is dry, it is removed from the glass, and forms a pliant tissue, ready for exposure under a negative, after which it is mounted (exposed face down) on paper, either temporarily, by means of caoutchouc cement, or permanently, by means of albumen. It is then developed, and, if temporarily mounted, is re-transferred, as we shall describe. The second and usual method consists in the application of the gelatine and coloring matter to paper, which can be rendered sensitive, when required, by immersion in a solution of bichromate of potash. It is then exposed under a negative, attached to another temporary basis of paper by a waterproof cement, the first paper being readily removed by soaking in warm water, so as to expose to the water the side of the film-opposite to that which was in contact with the negative, the development and transference following in due course. We shall describe both these methods in detail.
A patent has been issued to John C. Crosman, Boston, Mass., for an "Improved Process of Coating Sheets of Paper and Other Material with Solutions." His specifications read as follows:
