REPORT OF MR. W. J. STILLMAN.
357
character, not subjects for an exhibition, much less of commercial value.
The original daguerreotype was a positive photograph, incapable of multiplication ; but the law of the reduction of silver, under the joint action of light and a developing agent, having once been made known, practical investigators soon worked out the bases of the negative processes now in use,— the first being the paper process, introduced by Talbot, and now abandoned except by amateurs, who find its pictorial advantages and practical convenience more than a compensation for the greater delicacy and perfection of the detail which are obtained by the processes which employ a film of the sensitive salts spread on glass. There was no contribution of works by the original paper process in the Exhibition ; and there seems never to have been any serious attempt made to produce a satisfactory substitute for the fragile glass,—the precarious foundation of all our present effective processes. With the introduction of the collodion process and the modifications which the experience of photographers have found advisable, progress seems to have stopped, so that most of the work shown at Vienna is produced by the wet collodion negative process, substantially as introduced by Archer in England about a quarter of a century ago. In the many and useful modifications of it, the English photographers, amateur and professional, have distinguished themselves beyond all rivalry; and especially in the perfection of dry collodion processes, which, for all out-of-door work, where portability is an advantage, for tourists’ uses and for architects and amateurs’ work generally, have become a notable feature in the status of the art. All who have attempted the Manipulations of photography under the difficulties which portable or improvised dark rooms present, with all the chances and disasters of broken apparatus,—chemicals poured over delicate mechanism and mixed in waste,—or who, under urgent need of working at inaccessible stations, have found how cumbersome is the most portable apparatus for the working of the ordinary process, will appreciate the desirability °f a modification of it, by which sensitive films of equal rapidly, capable of indefinite preservation and always ready for use without the necessity of apparatus either for prepara-