THE pictures in the National Gallery are arranged according to the schools of painting in their historic order, thus enabling one to treat of its treasures in a very satisfactory way, by natural rogression. The comparative value of the schools may come within the scope of this book, although, since the chain is not absolutely complete, and some examples are necessarily missing, it is not the authors intention to claim that she offers a history of the various scllools of art. Only so far as it is possible to illustrate by examples, will the historic continuity be emphasized. In tracing the early history of the art of painting, it has been thought more interesting to consult the original authorities and the contemporary treatises, rather than later commentators, when dealing with technical processes, such as tempera, fresco, encaustic, and oil-painting. As the spelling of the names of foreign painters is often made a subject for discussion, the orthography of the Official Catalogue of...