Another mode of division is afforded by the difference of the medium employed to attach the colours, and in which they are ground or with which they are mixed, and both of these modes of classification and differentiation will be made use of in this handbook.

The first process treated of is true fresco, "buon fresco," which was for a long time considered the ideal mode of decorating a wall-surface, and which prescribes certain conventions which are undoubtedly advantageous to the work; fresco secco and tempera come next, as being closely connected with it, and the modern processes of water-glass or soluble silicate follow, for which absolute permanence is claimed. In all these processes the medium in which the colours are ground is pure water. Next the processes in which wax and essential oils are used are described, and finally those which are simply modifications of ordinary oil painting applied to a wall. The preparation of the wall itself is of the greatest importance to the permanence of any painting which may be attached to it, or executed upon it, and a few general remarks may be made which are applicable to all grounds; but the mode of final treatment differs so greatly in different processes that details must be given of the preparation under each head, necessitating a certain amount of repetition for which the author hopes he may be forgiven.

While a certain amount of historical detail is inseparable from the treatment of such a subject as mural painting, it is evident that anything like a com-plete summary of styles and schools, giving their distinguishing marks and characteristics, cannot be attempted in handbooks of the nature of those in this series without making them overbulky and unwieldy; and there has, therefore, been no attempt to give anything but the merest suggestion in the present case.

The following books have been consulted: Vitruvius, and Pliny's Natural History ; Didron's translation of the Mount Athos Manual, Hendrie's Theophilus, Mrs. Herringham's Cennini and Mrs. Merrifield's translation of the same book, Sir Charles Eastlake's Materials for a History of Oil Painting, HittoriFs Restitution du temple d'Empddocle & Selinonte, Cros and Henry's L} Encaustique et les autres procidis de peinture chez les anciens, Paillot de Montabert's Traite complet de la peinture, Taylor's Manual of Fresco and Encaustic Painting, Latilla's Treatise on Fresco, Encaustic, and Tempera Painting, Catalani's La Chiesa di S. Angelo in Formis, Schulz's Denkmciier der Kunst Unter Italiens, Helbig's Wandgemdlde der vom Vesuv verschiitteten Stadte Cam-paniens and other papers, Burckhardt's Le Cicerone, Forni's Manuale del pittore restauratore, Armenini's Dei Veri Precetti delta Pittura, Lopez9 H bcUtistero di Parma, Tommaselli's Delia Gerografia, Selvatico on Oil Painting and Tempera, The chronicle of Fra Salim-bene, iSm&ic- David's Histoire de la peinture au moyen dge, Merimee's Handbook of Oil Painting, Gambier Parry's account of his process of Spirit Fresco, Armitage's Lectures on Painting, Professor Church's Chemistry of Paints and Painting, Professor Baldwin Brown's Lectures on Art, The Journal of the Franklin Institute, The Journal of the Society of Arts, The Art Journal and the Quarterly Review and several Encyclopaedias, the Zeitschrift ftor BUdende Kunst, and many articles in the publications of the various Italian historical societies known as the Reali DeptUasdoni per Storia Patria, published in the different districts of Italy. The object has been to focus, as far as may be, the information scattered through many publications. Those interested in encaustic painting will find excellent practical notes in Carpentier's Notes sur la peinture & la dre cauterisee.