The method of removing the films from collodion plates by means of a coating of transfer collodion, and subsequently either remounting them upon the glass in a reversed position to be utilised in processes requiring "reversed negatives," or preserving them as "tissue" negatives, in which form they may be printed from either side, will be familiar to most readers. The application of the process to gelatine plates presents somewhat more difficulty. Following are a few particulars of the treatment found by Wilfred Bailey successful.

The collodion is prepared from one of the usual formulae for the purpose, as follows: Ether, 5 oz.; alcohol, 0'805, 10 oz.; castor oil, 1/4 oz.: pyroxyline, 1/4 oz.

The gelatine negative (in a dry, and, of course, unvarnished condition) is flowed liberally with the collodion, levelled, and allowed to dry. The film is then cut through to the glass at a short distance from the edges, and the plate is left to soak in water for some 24 hours, after which it will be found that the film may be lifted by a corner, and easily detached from the glass. It may then be reversed, and laid upon the glass under water in a similar manner to that adopted with carbon tissue, the superfluous water being afterward gently pressed out, care being taken not to injure the gelatine surface, which is somewhat tender at this stage. The plate should then be allowed to dry (not too quickly, or the film will have a tendency to peel off the glass). If only a reversed negative is wanted, it is now ready for use; but if a tissue negative is desired, the plate should again be flowed as before with the collodion, dried, cut round, either at the edges where previously cut, or to any size and shape desired, and then soaked in water until it can be easily removed from the glass, which will be the case in a few minutes.

The film may then be dried in blotting-paper, and preserved between the leaves of a book (one interleaved with tissue paper will be found convenient for the purpose).

To print, the film may be laid upon a piece of glass in the printing frame, and will be found to lie flat without difficulty in a dry state; but, if desired, it may be mounted as before with the aid of water, and dried. In the latter case, it will be generally found necessary to soak the plate a few minutes in water when the film is to be removed from the glass. In all stages of the process where soaking in water is required, be careful to continue it long enough, as if any adhesion exists between the film and the glass, damage to the former will ensue on attempting to remove it.

Bailey was led to employ this method chiefly for the purpose of printing negatives by the single transfer carbon process, which he considers the best and most convenient (for an amateur especially) that exists, but he finds also great advantage in the small space occupied by the tissue negatives, and their portability. The tissue is very tough, and cannot easily be torn (unless a cut or tear has begun at the edges, in which case great care is requisite). The second coating of collodion acts as a protection to the enclosed gelatine film, and adds substance to the tissue, while it prevents the "cockling-up" which the sensitiveness of the gelatine to moisture causes if it is attempted to use the film as a tissue on its first removal from the glass, without a second application of the collodion as directed. Of course the same treatment may be applied to transparent positives, and might be useful for other purposes. {Photo. News.)