714

THEORY AND PRACTICE OF ENGINEERING.

Book II.

laid side by side, the tegula; the ends at the eaves being finished with those ornamentswe have termed the antefissa?. Pliny mentions them under the term j*ers»na , probably fromtheir resemblance to masks, and says they were invented by a Sieyonian potter namedDibutades, who was established at Corinth , where they were called protypes, from beingstamped in front only : other tiles fixed upon the ridge, executed by the same artist, weretermed eetypes.

Many very ornamental tiles were made use of, some of which were covered with plates ofmetal, either silver or bronze.

Fig. 599.

CONVEX TILES WITH COVERED JOINTS.

A more simple application consists of forming the tiles in such a manner that the cover-ing to the joints can be dispensed with; this is accomplished by making the lower tile

l'ig. GOO. CONVEX TILES LAID WITHOUT COVERED JOINTS.

with grooves at the edges, in such a manner that a portion of the upper may enter and keepout the weather.

Tiles are sometimes laid diagonally, and with an undulating surface: the joints arethen sufficiently covered, and do not require any further protection.