Chat. XXIV.

MASONRY.

1423

the Greeks to that species of masonry inwhich the stones were of the same formand dimensions, but placed in courses ofunequal height; such stones had theirlength equal to double their width.

At Athens there are several wallswhich have the courses of masonry oftwo different heights alternating witheach other ; the small course is only two-thirds that of the other; consequentlythree stones form the entire thickness inthe one course, and two in the other orlarger one, which doubly ties the entirethickness of the wall.

DIATONOUS.

Fig. 2402.

PSEt'DISODOMON.

Another variety of masonry often met with in Italy bears some resemblance to thosealready described, but instead of presenting in the same course one header and onestretcher alternating, there is a course of headers and one of stretchers, like the oldEnglish bond in brickwork : as the headers pass entirely through the wall, the work isrendered very solid.

Fig. 2403.

Isodomum: the courses are all of equal height, producing both durability and solidity;first, because the stones are hard and solid, and therefore unable to absorb the moistureof the mortar, which is thus preserved to the longest period; and secondly, becausethe beds being smooth and level, the mortar does not escape, and the wall is bondedthroughout the entire thickness.

To the admirers of solid construction we cannot do better than refer to the various methodsemployed in the amphitheatre of Vespasian at Rome: amidst the ruins of that stupendouspile, we yet observe specimens of almost every style of masonry, and a judicious applicationof stones of different degrees of hardness: brick and tile, with every kind of backing orfilling in, was made use of where economy was desirable, or could be practised withoutsacrificing stability and strength; the large stones are wrought on all their faces, to suittheir position around an oval plan, or circular on the elevation. The Coliseum is not only