Before beginning to paint, damp the wall till it absorbs no more water; the dampness affords time to unite the colours and give suavity and freshness to the distemper. Begin with the pale tones and work downwards to the half-tones and the browns. Distemper requires a decided and single painting. It can be retouched, but the same colours must be employed, otherwise muddiness will result from the mixing of a different over- and under-colour. Tints may be united at once with a brush dipped in pure water. Glazing may sometimes be used, but a light hand and a very soft brush are required, with great rapidity of execution. Before attempting it, pass a wash of size over the place. Sometimes the touches will not "take," the ground being too much charged with size. Then mix ox-gall with fresh colour. If you wish to retouch after the colour has dried you must moisten the place with your finger and saliva; every other way makes a patch. The effect of retouching is that the added touches stand out disagreeably like a coarse mosaic. The best way is to place the fresh tints when the painting is half dry so that the upper touches may not drag up the lower tint. De Montabert also says: " The rapidity of drying may be lessened by adding viscous juices to the medium, such as those from the bark of mistletoe, the roots of viburnum, the juice of elder, narcissus roots, or other bulbous plants, or sn$il slime; fig juice has always been employed for this purpose. Sugar, honey, or syrups of marsh mallow or jujube also will lessen the speed of drying, but they become yellow, and absorb moisture constantly." Egg forms the best medium, and volatile oil of wax might be mixed with the size advantageously. Red draperies may be painted successfully with red lead and glazed with lake; yellow draperies may be glazed with gamboge. Blue draperies may be sketched in red ochre and glazed with blue. The fifteenth-century painters obtained greens by glazing yellow over ultra' marine, examples of which may be seen at S. Croce in Gerusalemme at Rome. The colours which cannot be employed are vermilion and brown-pinks. Wash-ing over with weak size, however carefully and lightly done, always reduces brilliancy, but if gold is to be added it has to be done. The mordant is then put on; it is thick glue with a little honey added. The hatchings are put on with the point of a brush, with the material in a warm state and pretty thick. When it is firm the gold is applied and allowed to dry for several days. Care must be taken that the preparation does not sink into the colour, which may be discovered by its losing its shine, for then it loses its adhesiveness, and the operation has to be gone through again.