I must remind you now of the expression as to the building of the communal palace--"of _dressed_ stones" [1]--as opposed to the Tower of the Death-watch, in which the grip of cement had been so good. Virtually, you will find that the schools of structural architecture are those which use cement to bind [Footnote 1: "Pietre conce." The portion of the has-reliefs of Orvieto, given in the opposite plate, will show the importance of the jointing. Observe the way in which the piece of stone with the three principal figures is dovetailed above the extended band, and again in the rise above the joint of the next stone on the right, the sculpture of the wings being carried across the junction. I have chosen this piece on purpose, because the loss of the broken fragment, probably broken by violence, and the only serious injury which the sculptures have received, serves to show the perfection of the uninjured surface, as compared with northern sculpture of the same date. I have thought it well to show at the same time the modern German engraving of the subject, respecting which see Appendix.] [Illustration: PLATE VIII.--"THE CHARGE TO ADAM." GIOVANNI PISANO.] their materials together, and in which, therefore, balance of _weight_ becomes a continual and inevitable question. But the schools of sculptural architecture are those in which stones are fitted without cement, in which, therefore, the question of _fitting_ or adjustment is continual and inevitable, but the sustainable weight practically unlimited. 162. You may consider the Tower of the Death-watch as having been knit together like the mass of a Roman brick wall. But the dressed stone work of the thirteenth century is the hereditary completion of such block-laying, as the Parthenon in marble; or, in tufo, as that which was shown you so lately in the walls of Romulus; and the decoration of that system of couchant stone is by the finished grace of mosaic or sculpture. 163. It was also pointed out to you by Mr. Parker that there were two forms of Cyclopean architecture; one of level blocks, the other of polygonal,--contemporary, but in localities affording different material of stone. I have placed in this frame examples of the Cyclopean horizontal, and the Cyclopean polygonal, architecture of the thirteenth century. And as Hubert of Lucca was the master of the new buildings at Florence, I have chosen the Cyclopean horizontal from his native city of Lucca; and as our Nicholas and John brought their new Gothic style into practice at Orvieto, I have chosen the Cyclopean polygonal from their adopted city of Orvieto. Both these examples of architecture are early thirteenth century work, the beginnings of its new and Christian style, but beginnings with which Nicholas and John had nothing to do; they were part of the national work going on round them.