so powerless a brightness as white paint can only acquire the splendour of light by great contrast, and, above all, by being seen through external darkness. The secret of Van Eyck and his contemporaries is always assumed to consist in the vehicle (varnish or oils) he employed; but a far more important condition of the splendour of colour in the works of those masters was the careful preservation of internal light by painting thinly, but ultimately with great force, on white grounds. In some of the early Flemish pictures in the Royal Gallery at Munich, it may be observed, that wherever an alteration was made by the painter, so that a light colour is painted over a dark one, the colour is as opaque as in any of the more modern pictures which are generally contrasted with such works. No quality in the vehicle could prevent this opacity under such circumstances; and on the other hand, provided the internal splendour is by any means preserved, the vehicle is comparatively unimportant.
It matters not (say the authorities on these points) whether the effect in question is attained by painting thinly over the ground, in the manner of the early Flemish painters and sometimes of Rubens, or by painting a solid light preparation to be afterwards toned to richness in the manner of the Venetians. Among the mechanical causes of the clearness of colours superposed on a light preparation may be mentioned that of careful grinding. All writers on art who have descended to practical details have insisted on