8. _Small specks and spots of different hinds._--These, when not corresponding to similar marks upon the Negative, are usually due to metallic specks in the paper; or to insoluble particles floating in the bath. 9. _Markings of the brush in Ammonio-Nitrate pictures._--In this case there is probably an excess of Ammonia, which dissolves the Chloride of Silver. Add a little fresh Nitrate of Silver, or use the Oxide of Silver dissolved in Nitrate of Ammonia (p. 249). 10. _Marbled stains on the surface of the Print._--Draw a strip of blotting-paper gently over the surface of the Nitrate Bath before sensitizing the paper; and see that the sheet does not touch the bottom of the dish. 11. _Streaks on Albuminized paper._--Apply the Albumen more rapidly and evenly to the paper. If this does not succeed, add a little Ox-Gall (p. 243). 12. _Removal of the Albumen from the paper during sensitizing._--The Nitrate Bath is probably alkaline (see page 89). CHAPTER VI. LANDSCAPE PHOTOGRAPHY ON PRESERVED COLLODION AND COLLODIO-ALBUMEN. The Collodion process may be applied with success to landscape Photography; but as the plates become dry and lose their sensitiveness shortly after their removal from the Bath, the operator will require to provide himself with a yellow tent or some portable vehicle in which the operations of sensitizing and developing can be conducted. As it is a point of great importance in the Collodion process that the plate should receive exactly the right amount of exposure in the Camera,--a few seconds more or less sufficing to affect the character of the picture,--many will submit to much trouble and inconvenience in order to have the apparatus complete upon the spot at which the view is taken. The object of the "Collodion Preservative Processes" is to maintain the sensitiveness of the film for a certain length of time after it has been excited in the Bath. There is some difficulty in doing this, because if the plate be allowed to dry spontaneously, the solution of free Nitrate of Silver upon the surface, becoming concentrated by evaporation, eats away the Iodide of Silver, and produces transparent spots. Some operators have attempted to use a second plate of glass in such a way as to enclose the sensitive film with an intervening stratum of liquid. The difficulty however of separating the glasses again without tearing the film, is considerable. In the process of Messrs. Spiller and Crookes, the property possessed by certain saline substances of remaining for a long time in a moist condition was turned to account. Such salts are termed "deliquescent," and many of them have so great an attraction for water that they absorb it eagerly from the air: the solution having been formed, the water cannot entirely be driven off except by the application of a considerable heat.