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Rh had been so good. Virtually, you will find that the schools of structural architecture are those which use cement to bind 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