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Rh are so firm, and as the building must never stir or settle after it is built, the sculptor may trust his work to two stones set side by side, or one above another, and carve continuously over the whole surface, disregarding the joints, if he so chooses.

Of the degree of precision with which Nicholas of Pisa and his son adjusted their stones, you may judge by this rough sketch of a piece of St. Mary's of the Thorn, in which the design is of panels enclosing very delicately sculptured heads; and one would naturally suppose that the enclosing panels would be made of jointed pieces, and the heads carved separately and inserted. But the Pisans would have considered that unsafe masonry,—liable to the accident of the heads being dropped out, or taken away. John of Pisa did indeed use such masonry, of necessity, in his fountain; and the bas-reliefs have been taken away. But here one great block of marble forms part of two panels, and the mouldings and head are both carved in the solid, the joint running just behind the neck.

168. Such masonry is indeed, supposing there were no fear of thieves, gratuitously precise in a case of this kind, in which the ornamentation is in separate masses, and might be