[Illustration: Fig. 128.--Portal upon Samos.]
[Illustration: Fig. 129.--Gate of Phigalia.]
The form of three blocks appears to have been soon changed, the wall itself serving in place of an especial jamb. The span of the lintel was decreased by two or four boldly projecting blocks as brackets. Examples of this development are offered by portals of Samos and Phigalia. (_Figs._ 128 and 129.) But in the same measure as the danger from the great span of the lintel was diminished, that of the brackets being pressed downward and disjointed was increased. A third manner of covering the opening, by stones leaned against each other at an angle, was a still further advance. (_Fig._ 130.) When the side thrust could be well borne--and for this the walls were always sufficient--such a gable could support any pressure that could possibly be imposed, while allowing a great breadth of passage. Finally, a triangular construction could be obtained by a gradual projection of horizontal stones, laid as they had been in so many instances for the relief of a lintel beneath them. This construction occurs in two varieties, differing in appearance, though not in principle: the projection of the horizontal courses of stone either began directly from the ground (_Fig._ 130), as has been noticed in the Tholos of Atreus (_Fig._ 122), or commenced at some height, the jambs being carried up vertically. (_Fig._ 132.) In both these varieties the line of the gable frequently appears concavely curved, as in the parabolic walls of the tholos, and the outline of a pointed arch was thus obtained. (_Figs._ 133 and 134.) In spite of their early familiarity with the abstract principle of the arch, as shown in _Fig._ 130, the Greeks refused to adopt the true arch, with its wedge-shaped stones, even in late historical ages, when they assuredly were acquainted with its construction. An illustration of their feeling in this respect is given by the aqueduct adjoining the Tower of the Winds in Athens, where the semicircles are cut from monoliths.
[Illustration: Fig. 130.--Portal upon Delos.]
The influence of the gateways upon the masonry is evident from the more frequent adoption of the rectangular blocks, which had at first only been employed to give the portals an independent strength, both for the ramparts and for the out-works and protecting towers which these openings necessitated. Such a fortification, erected for the defence of a gate, still stands in Tiryns--the city to which succeeding ages ascribed the invention of tower-building (Pliny, _Hist. Nat._ vii. 56); it reaches a height of 13 m. Thetower which defended the gate of Mykenæ was even larger. Homer mentions such structures at Troy, Thebes, and Calydon, and is also familiar with casemates and battlements. The latter are shown by paintings upon archaic vases to have been of the normal rectangular shape.