improved on a hint borrowed from the early German painters, many of whom painted on glass.79
At all events, the principle of still increasing in colour in certain hues seems to have been adopted in Flanders and in Venice at an early period;80 while Giorgione, in carrying the style to the most daring extent, still recommended it by corresponding grandeur of treatment in other respects.
The same general tendency, except that the technical methods are less transparent, is, however, very striking in some of the painters of the school of Umbria, the instructors or early companions of Raphael.81 The influence of these examples, as well as that of Fra Bartolommeo, in Florence, is distinctly to be traced in the works of the great artist just named, but neither is so marked as the effect of his emulation of a Venetian painter at a later period. The glowing colour, sometimes bordering on exaggeration, which Raphael adopted in Rome, is undoubtedly to be attributed to the rivalry of Sebastian del Piombo. This painter, the best of Giorgione's imitators, arrived in Rome, invited by Agostini Chigi, in 1511, and the most powerful of Raphael's frescoes, the Heliodorus and Mass of Bolsena, as well as some portraits in the same style, were painted in the two following years. In the hands of