To produce photographs in relief, soak some fairly stout sheet gelatine for half an hour in a 5-per-cent. solution of potassium bichromate. This reuders the gelatine sensitive to light on drying, which must take place slowly in a well-ventilated and dark room. It is advisable to squeeze the gelatine down on to plate glass (as in enamelling a print); the glass gives the gelatine a good smooth surface for rendering minute detail. When dry the gelatine is stripped from its glass support and exposed beneath a negative. The bichromated gelatine when exposad to light becomes insoluble and incapable of absorbing moisture in proportion to the intensity of the light's action on it. If the gelatine be now placed in cold water those portions of gelatine unaffected by light will begin to swell. As this expansion or swelling will be in width as well as thickness, the gelatine should be fixed with isinglass to an insoluble support; this compels the gelatine to swell upwards. If a cast is taken of this picture in relief the modelling will be negative and reversed. Therefore, proceed as follows. A positive showiug a good degree of contrast and gradation, such as would be suitable for carbon printing, must be first taken.

This positive should be thin and full of detail, with the lights and shades due as far as possible to form. To remedy the false relief due to colour, intensify with uranium and remove the effect locally as desired with a weak solution of ammonium hydrate. After printing, thoroughly soak the gelatine in a dish, then carefully remove and blot off all moisture, oil the gelatine mould and drain off the excess, and place the mould in a sort of tray made by bending up the edges of a piece of stiff paper. Mix up some fine plaster-of-Paris and pour it over the mould. Another method that may be used where only general effect is required is described below. A pad consisting of a board covered with velvet or plushette will be required, together with some modelling tools and a board covered with carbon paper. A print is mounted with seccotine or other cement on a thin sheet of soft lead; on the other side is pasted a sheet of white paper. Lay the mounted print, face up, on the carbon paper and trace on the print all the parts of the picture that should stand in relief. Lay the print face down on the plush block, and, using the traced lines on the back of the print as guides, press out those parts that are to be in relief.

Now turning the print over (that is, letting it lie face upwards) press back the shadows, putting in any sharp edges with the pointed end of the tool. As the print is fastened to the metal the shape of the print will remain unaltered, and it may be mounted on a card with gelatine. Platinotypes give the most satisfactory results with this process, both on account of their colour and their malleability. The process is so simple that artistic ability and practice are all that are needed in order to obtain the best results.