The greatest demerit of dark grounds is, that they tend ultimately to show through and obscure the superimposed colour. Gaspar Poussin's grounds are of this description; and there is little doubt that the examples of this master in the National Gallery are from this cause lower and more gloomy in tone than was originally intended. Velazquez and Murillo painted upon the red-earthy preparations with which the Spanish canvas has almost uniformly been charged. The Caracci, and W.Vandevelde, likewise painted on a dark ground.