Secondly, the print, from not being attached to the mount all over, is apt, especially when in a large size, to be somewhat wavy and wanting in flatness.  Another plan recommended, as giving a surface resembling albumen paper, is to paste the back of the print without moistening the surface, and so mount.  Some prints that have been shown thus treated had so strongly curled the cards upon which they were mounted that it is evident there was considerable strain and consequent distortion.

A third plan recommended is to paste the back of the print while in contact with the glass upon which it has to dry; and, when dried, to mount by passing through a rolling press with a damped card.  This plan looks, at first sight, like that recommended for albumen paper, and called “dry” mounting.  Consideration, however, will show that there is a radical difference.  In the case of the albumen paper the print has been dried without strain, and therefore but little change is to be looked for, while the print dried in contact with glass is strained to the utmost, causing present distortion and future curling of the mount.  Perhaps the evil of distortion caused by enameling may be reduced to a minimum by soaking the print in alcohol previous to laying it upon the glass.

Since the distortion of the photograph arises from the unequal expansion of the paper when wet, it becomes a question whether something may not be done in the selection of the paper itself.  It may be that some makes vary much less than others in the “length against width” extension of the surface by wetting.  It must be remembered that for gelatine emulsion we are not nearly so limited in the selection of paper as when it is required to be albumenized.  In the latter case the image is in the paper, whereas with gelatine the image is contained in the surface coating.  I may mention that the best plain, i.e., not enameled, but resembling that of ordinary albumen paper, surface that I have seen upon gelatine paper was upon some foreign post that I had obtained for another purpose.  The emulsion employed was that described by Mr. J.B.B.  Wellington, and this gentleman agreed with me in attributing the superiority of the surface obtained to the fine quality of the paper upon which the emulsion had been coated.  Some commercial samples appear to be coated upon paper of somewhat coarse texture.  This does not show when the print is enameled.

The unequal expansion of paper is a subject of interest, not only in connection with gelatine paper for development, but with various photographic processes.  In making carbon transparencies for instance, the gelatine film which is squeegeed against the glass necessarily takes its dimensions from the paper to which it is attached, and if that be expanded more in the one direction than another, the transparency is similarly deformed; and so, of course, is any negative, enlarged or otherwise, produced in the camera therefrom.  A reproduced negative by contact printing may either have the distortion due to expansion of the paper bearing the gelatine film removed or doubled, according to the direction in which the paper is used for the new negative.—­W.E.  Debenham, in Br.  Jour. of Photography.