ROMAN ARCHITECTURE. 165 The use of the true arch is avoided. An example of a vaulted building is the Treasury of Atreus, at M}-- cenas, where the beds of the stones are horizontal throughout, each bed oerlapping the one below till the crown is reached (page 54). The Greek Temples were usually orientated, i.e., faced the east. B. W^alls. — Constructed of large blocks of marble, without mortar, allowing of refinement of treat- ment, and perfection of finish in construction. Where coarse stone was used it was frequently covered with stucco. Jointing was not reckoned as a means of effect. Stabilit}' was achieved solely by the judicious observance of the laws of gravity, the adher- ence of the blocks not being necessary, for the weights only acted vertically, and needed but vertical resistance. Even for transmitting the pressure be- tween the blocks only metal cramps were used. The employ- ment of marble directly shaped the development of the style. One-sixteenth of an inch was rubbed off the buildings on completion, this polishing being performed by slaves. The Aiita (Nos. 21, 26, 27 l, 30, and 44 f) was employed at ex- tremities and angles of cella walls. c. Openings.— Of minor import- ance, the columnar treatment giving the necessary light and shade. Doorways are square- headed, and often crowned with a cornice supported by consoles, as in the fine example of the north doorway at the Erech- theion, Athens (No. 37 d — h). Windows, except on rare occasions, as shown on plate No. 28, were not used in Temples, illumination being obtained from doorways or hyptethral openings (Nos. 20 c, 23 A, B, and 27 B, d). ROMAN. vaults, by which the concentra- tion of weights on piers was effected. The use of recesses rectangular and semicircular on plan is a special Roman feature (Nos. 50 B, 54 b). The Roman Temples were placed without regard to orientation. B. ^A^alls.— Constructed of small, mean, and coarse materials, such as brick, rubble, and concrete, with brick or marble facing, bond courses for strength being intro- duced. Such walls are thus often coarse in character. By the ex- tended use of concrete, it may be said that the Romansinaugurated the employment of large masses of irregular materials, reduced into fragments and bound together by mortar. These materials were not special to any country, but consisted of frag- ments of stone, brick or hard rock and quarry debris, all of which sufficed for the most important projects. Great haste was necessary in the execution to complete sufficiently for use, and doubtless many buildings were never perfectly finished. The pilaster was the Roman de- velopment of the Greek Anfa (Nos. 38 F and 67 f). c. Openings. — These were im- portant features, being square- headed or circular, principally the latter (No. 62 a). The semicircle divided vertically by two muUion piers was a favourite type of window. Arches some- times had centering, supported at the springing line, after- wards filled up with brick- work, thus producing the seg- mental arch, common in the third and fourth centuries a.d. (No. 46 e), from the Basilica of Constantine.
