§ VI. It is, however, I believe, sometimes supposed that rustication gives an appearance of solidity to foundation stones. Not so; at least to any one who knows the look of a hard stone. You may, by rustication, make your good marble or granite look like wet slime, honeycombed by sand-eels, or like half-baked tufo covered with slow exudation of stalactite, or like rotten claystone coated with concretions of its own mud; but not like the stones of which the hard world is built. Do not think that nature rusticates her foundations. Smooth sheets of rock, glistening like sea waves, and that ring under the hammer like a brazen bell,--that is her preparation for first stories. She does rusticate sometimes: crumbly sand-stones, with their ripple-marks filled with red mud; dusty lime-stones, which the rains wash into labyrinthine cavities; spongy lavas, which the volcano blast drags hither and thither into ropy coils and bubbling hollows;--these she rusticates, indeed, when she wants to make oyster-shells and magnesia of them; but not when she needs to lay foundations with them. Then she seeks the polished surface and iron heart, not rough looks and incoherent substance. § VII. Of the richer modes of wall decoration it is impossible to institute any general comparison; they are quite infinite, from mere inlaid geometrical figures up to incrustations of elaborate bas-relief. The architect has perhaps more license in them, and more power of producing good effect with rude design than in any other features of the building; the chequer and hatchet work of the Normans and the rude bas-reliefs of the Lombards being almost as satisfactory as the delicate panelling and mosaic of the Duomo of Florence. But this is to be noted of all good wall ornament, that it retains the expression of firm and massive substance, and of broad surface, and that architecture instantly declined when linear design was substituted for massive, and the sense of weight of wall was lost in a wilderness of upright or undulating rods. Of the richest and most delicate wall veil decoration by inlaid work, as practised in Italy from the twelfth to the fifteenth century, I have given the reader two characteristic examples in Plates XX. and XXI. [Illustration: Fig. LXI.]