“His idea, therefore, of rock color, founded on these experiences, is that of a dull or ashen gray, more or less stained by the brown of iron ochre, precisely as the Apennine limestones nearly always are; the gray being peculiarly cold and disagreeable. As we go down the very hill which stretches out from Pietra-pana towards Lucca, the stones laid by the roadside to mend it are of this ashen gray, with efflorescences of manganese and iron in the fissures. The whole of Malebolge is made of this rock, ‘All wrought in stone of iron-colored grain.’ ”