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Athens, and the walls of Peiraeeus, the massiveness of the Cyclopaean works was united with perfect regularity of construction. The stones, which were so large that each was a cart-load (afjLa^iaioi) were accurately fitted to'one another (eV ro/^fj syy&vioi), and held together, without cement by metal clamps soldered with lead into sockets cut into the blocks of stone. (Thuc. i. 93). The walls of the Par-thenon, and the other great edifices of the period, were of similar construction. Sometimes wooden plugs were used instead of metal clamps. It is unnecessary to describe here the details of the modes in which the joints were arranged in this regular and massive masonry. So perfect was the workmanship at this period of the art, that the joints often appeared like a thread ; and Pliny mentions a temple at Cyzicus, in the interior wall of which a fine thread of gold was actually inserted in the joints of the masonry. (H. N. xxxvi. 15. s. 22.)
The materials employed at this period were various sorts of stone, and, in some of the most magnificent temples, marble. The practice of putting a facing of marble over a wall of a commoner material was introduced in the next period of architectural history. The first example of it, according to Pliny (H. N. xxxvi. 6. s. 6), was in the palace of Mausolus, the walls of which were of brick, faced with slabs (crustae) of Proconnesian marble (about b. a 360). Vitruvius (ii. 8) also' states this fact, and adds that brick walls, when perfectly perpendicular, are quite as durable as those of stone, and, in proof of this, he mentions several examples of very ancient brick buildings, both in Greece and Italy. (Comp, Vitruv. i, 42 ; Pans. i. 42, ii. 27, v. 5, x, 4, 35 ; later.)
For buildings of a common sort, the materials employed were smaller stones, rough or squared, or flints, as well as bricks: the latter, however, were not nearly so much used by the Greeks as by the Romans. The different methods of construction will be described presently.
The walls of smaller quarried stones or bricks-were bound together with various kinds of mortar or cement, composed of lime mixed with different sands and volcanic earths. The most durable of these was the cement formed by mixing two parts of Terra Puteolana (Puzzolana^ a volcanic product^ which is found in various parts of Italy, besides Puteoli) with one part of mortar: this cement had the property of hardening rapidly under water: it was much used in aqueducts, cisterns, and such works. (For further details on cements, see Vitruv. ii. 5, 6, v. 12, vii. 2 ; Plin, //. N. xxxvi. 23. s. 52, 55 ; Pallad. i. 10, 14 ; Strab. v. p. 245 ; Dioscor. v. 133),
The history of Roman masonry is not very different from that of the Greek. The Cyclopean remains of Italy have been already noticed. The most ancient works at Rome, such as the Career Mamertinus, the Cloaca Maxima, and the Servian Walls, were constructed of massive quadrangular hewn stones, placed together without cement, [cloaca.] In most of the remains, the stones are twice as long as they are high. Canina (Arch. Antiq.} distinguishes five species of Roman masonry; namely, (1) when the blocks of stone are laid in alternate courses, lengthwise in one course, and crosswise in the next; this is the most common; (2) when the stones in each course are laid alternately along and across ; this construction was usual when
the walls were to be faced with slabs of maible ; (3)_ when they are laid entirely lengthwise ; (4) entirely crosswise ; and (5) when the courses are alternately higher and lower than each other, as in the round temple (of Vesta, so called) upon the Tiber. This temple also affords us an example of what is called rustic-work, in which the stones are bevelled at their joints, the rest of their surfaces being generally left rough. This style of work originated, in the opinion of some, from the desire to save the trouble of smoothing the whole face of the stones ; but it is more probable that it was adopted in order to give a bolder and firmer appearance to the structure. Examples of it are found in the remains of several Roman fortifications in Germany, and in the substructions of the bridge over the Moselle at Coblenz (Rhein. Mus. 1836, vol.iv. p. 310 ; Witzschel, in the Real-Encydop. d. class. Alterth. art. Muri). As by the Greeks, so by the Romans, walls of a commoner sort were built of smaller quarried stones (caementa) or of bricks. Vitruvius (ii. 8) and Pliny (H. N. xxxvi. 22. s. 51) describe the following kinds of masonry, according to the mode in which the small stones (caementa} were put together. (The woodcut is copied from the AUnldungen zu Winckelmann's Werke, Donaubschingen, 1835, fig. 10.)
Besides the large square blocks of stone (0), thejr used smaller quadrangular stones arranged in regular courses of equal and of unequal heights; the former was called isodomum (M), the latter pseudisodommn (L)j. in another sort of work, called emplecton (G), the1 outer faces of the walls only were of wrought stones, the intermediate parts being filled up with rough stones, but these, in the Greek method of construction, were well bedded in mortar, and arranged with overlapping joints, and the wall was bonded together with stones laid across at intervals, which were called Siwrovoi (F); but the workmen of the time of Vitruvius were in the habit, for the sake of despatch, of running up the outer walls separately, and then filled the middle space with loose rubbish, a sort of work which Pliny calls diamicton. The excellence of the cement which the Romans used enabled them to construct walls of very small rough stones, not laid in courses, but held together by the mortar; this structure was called opus incertum (N). An improvement upon it in appearance, but inferior in stabilitj7", was the opns reiiculatum, of which there were two kinds, the like (K) and the unlike (I). This sort of work was composed of stones or bricks, from six to nine inches long, and about three inches square at'the end, which formed the faces of the