pended to drain for some hours, or submitted to pressure to remove the superfluous water; a perfectly even film of moisture is thus secured. The transfer is effected by laying the print face up on the steel plate of the press, and over the print is laid the moistened paper, and on that a felt blanket. The press is then “pulled.” The print is next immersed for an hour in a bath, containing five per cent, of alum, and is afterwards well washed in water and dried, after which it is uncovered as when mounted on cardboard.
By transferring to paper, it will be observed that facility is afforded for performing the last-mentioned operation, by which an additional source of stability is secured. The only possible source of deterioration in the prints produced by the method we have described, exists in the thin coating of gelatine with which the print is attached to its final support. By means of moisture and friction the print could be removed; this, it is true, is destruction, not fading or instability in its usual sense. But it is happily possible to remove even this susceptibility to injury. Although the transference of the print direct to cardboard has the advantage of making an exceedingly neat finish to the mounting (the print being slightly recessed in the cardboard), and although it has the further advantage of reducing the number of operations required to complete the picture, yet Mr. Swan greatly prefers, and almost invariably adopts, the method of transfer to paper, chiefly because this method secures the most uniform adhesion, and because it allows the gelatine (used to cause the print to adhere to the paper), to be rendered water-proof—a property not possessed by the prints mounted direct to card. One of the means used by Mr. Swan to render the gelatine insoluble is quite novel, and constitutes one of the first applications of his discovery of the property possessed by salts of the sesquioxide of
