chromium of rendering gelatine insoluble. A solution of common alum has, to a certain extent, the power of waterproofing the prints, and generally fixture with alum is quite sufficient. Where, however, more thorough waterproofing is demanded, the prints, after transfer, should be treated with a one per cent, solution of chrome alum. Mr. Swan has shown us some prints very successfully transferred without a press. The transfer was effected with the gelatine solution ordinarily used, to which has been added one-twentieth of a ten per cent, solution of chrome alum. Prints intended for coloring in water colors should be chrome-fixed.
Mr. Swan generally adds a small proportion of a white pigment to the gelatine with which the transfer is effected, in order to give brilliancy to the whites of the picture, and to avoid the intervention of a transparent film between the under surface of the print and the paper to which it is attached.
THE SENSITIVE COLLODIO-GELATINE TISSUE.
The method of carbon printing with this tissue is better suited to the amateur than to the professional photographer. It involves more trouble than the use of the paper tissue, but the results are very beautiful; and as the photographer, in employing it, mixes his own preparations, he has certain points in color and intensity more completely under his own control than he could have in purchasing a ready-prepared tissue.
To prepare the Sensitive Collodio-Gelatine Tissue.—Take a sheet of plate-glass, free from blemishes or scratches, and clean it perfectly, finally rubbing the surface with a saturated solution of beeswax in ether. This is then wiped off with a clean cloth, leaving a scarcely percepti-
