464 Pkimitive Greeck: Mycenian Art. units of polygonal blocks, transverse beams would provide the mason with the requisite straight lines which the humblest abode cannot dispense with ; they supplied him with a continuous horizontal plane, restful to the eye amidst a maze of irregular materials ; they enabled him to set up his doors and windows in the wall and the roof. In after days, this function will be performed by kiln-baked bricks, arranged in bands to divide the surface of a rubble wall or ashlar work. It is an expedient frequently resorted to by the Roman builder and his modern colleague as well, whenever his materials are ill-defined or of no great size. The main defect of the method chosen by the Mycenian constructor is that it brings together elements of different Via, 179. — Troy. Masonry of ivall n powers of cohesion and durability. Wood, unless protected by paint or stucco, soon rots away and crumbles into dust. In brick walls this disadvantage is trifling enough, for the clay sets into a coherent mass of great strength, and although the timbers gradually fall away, leaving gaps behind, they have no effect on the solidity of the wall. The case is quite different in stonework, especially with bad mortar, as at Mycenje and Tiryns. As soon as the stone above the cross-beam is no longer supported by it, a collapse is the result, and in sympathy with it the upper part of the wall either leans over or falls ; this will be seen by a glance at Fig. 182, showing a piece of wall of the Mycenian palace.
