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CLOA´CA (ὑπόνομος), a drain. The removal of the sewage of cities by an extensive system of drains is as old as the Assyrian civilisation, for we find it carried out at Nineveh with great completeness, the brick vaulting assuming all the known forms of the arch, while the pavement is formed of flagstones. (Layard, Nineveh and Babylon, p. 54; Place, Ninive et l'Assyrie, p. 269.)

As a specimen of the drainage of a Greek city, we may quote that of Athens, the remains of which are described by E. Ziller (Mittheil. des deutsch. Inst. in Athen, 1877, pp. 117-119), who has traced it from the Kolokotroni street (though he thinks that it may have started nearer the old wall on the east side of the city) to the church of Kapnikarea, and thence in a northwesterly direction on the west side of Hermes street to the Dipylon. Air-shafts, about 6 metres in depth, at various points permit an investigation of the construction, in which at some places dressed Piraeus stone, at others brick, is used. Outside the Dipylon the drain enters a reservoir, from the sides of which small square or cylindrical canals lined with brick carried the contents towards the plain and the olive woods, thus apparently pointing to an ancient system of applying the refuse of a city to fertilise sewage farms. One of these canals appears to show traces of a contrivance for regulating the amount of sewage supplied, which leads Ziller to the conjecture that the sewage supply was let out to the farmers.

The admiration with which the cloacae of Rome were regarded by antiquity may be judged from the passage of Dionysius of Halicarnassus (3.67), in which he classes them with the aqueducts and the roads as the most magnificent works in Rome, and the best proof of the greatness of the empire. (Cf. Plin. Nat. 36. §§ 104-8; and Cassiodorus, Var. 3.30, “videas illic fluvios quasi montibus concavis clausos.” ) Remains of a system of cloacae have been found in so many of the Roman cities of North Italy and France that they may indeed be considered a mark of Roman civilisation, as characteristic as the aquaeductus and the via.

The chief of the ancient drains still existing in Rome is the famous Cloaca Maxima, which starts in the valley of the Subura at the foot of the Carinae, crosses the Forum under the S. end of the Basilica Julia, where it is exposed to view, thence under the Vicus Tuscus and the Velabrum, and after being again visible near the arch of Janus Quadrifrons, as is shown in the accompanying illustration, it enters the Tiber near the Temple of Hercules in the Forum Boarium, by an arch of lapis Gabinus or peperino, formed of three rings of voussoirs. We give an illustration showing this arch, surrounded by the more weathered tufa of the Pulchrum Littus or ancient quay wall. Its original dimensions were 12 ft. 4 in. in height and 10 ft. 8 in. in width, but one-third of its height is now choked up by mud. [p. 1.462]This triple peperino arch extends for about 40 ft. from the mouth; but in the rest of its course the drain is vaulted with a single arch of tufa

Cloaca Maxima.

voussoirs 2 ft. 2 in deep, with occasional bands of travertine. The masonry of the peperino arch especially is fine and of ancient character.

Present condition of the Cloaca Maxima.

This drain was no doubt constructed to carry off not only the sewage, but also the surface water from the surrounding slopes, which made the low ground traversed by the drain a swamp. Hence the early construction of this great work, which is attributed to Tarquinius Priscus by Dionys. and Pliny (ll. cc.), while Livy divides the honour between Tarquinius Priscus and Tarquinius Superbus (1.38, 56). Mommsen, however, thinks that while the scheme of drainage was instituted under the kings, this vaulted cloaca must belong to the republican period, erroneously stating that the vault is throughout of travertine, a stone characteristic of post-regal times, and holding that the arch was unknown even to the Greeks until the end of the fifth century before Christ (Hist. of Rome, 1.117, 490, Eng. trans. ; Seneca, Ep. 90.32). But in support of the earlier date, which is now generally assigned to the Cloaca Maxima, we may quote Etruscan instances, which are probably at least as early: for instance, the mouth of an ancient cloaca discovered at Graviscae by Dennis (Cities of Etruria, 1.433), consisting of an arch of 14 ft. span formed of voussoirs of uncemented tufa 5 ft. deep, and opening in a quay wall about 20 feet high.

Another cloaca running from the corner of the Via Paganica and the Piazza Mattei, under the Ghetto, enters the Tiber opposite to the Insula Tiberina. It is constructed of large uncemented blocks of peperino: this and other indications would assign it to the regal period. Like the Cloaca Maxima, it is still in use, having been connected with the drain dell' Olmo in 1600 (Narducci, Boll. dell' Inst. 1881, p. 209). These drains of the regal period probably follow the old lines of the streets, as they ran before the destruction of Rome by the Gauls.

In the quay wall not far from the mouth of the Cloaca Maxima may be seen two smaller arched openings, one of which is now dry; the other discharges the waters of the Aqua Crabra. These may be terminations of the cloacae of the Aventine, which were not constructed until the year 184 B.C., when M. Porcius Cato and L. Valerius Flaccus constructed new drains and repaired the existing ones. To this occasion possibly may be referred the statement of the contemporary C. Acilius, quoted by Dionys. (l.c.), that the mere repair of the drains cost 1000 talents. M. Agrippa, during his aedileship in 36 B.C., showed great zeal in the supervision of the cloacae, traversing them in a boat and cleansing them at his own expense (Plin. l.c.; D. C. 49.43), and constructed a cloaca to drain the Campus Martius, which was connected with the Thermae of Agrippa and the Aqua Virgo. This was discovered under Urban VIII., and is at present in use under the name of the Chiavica della Rotonda.

The discoveries made at various times show that the network of smaller drains communicating with these main cloacae still exists, though in great part choked up. Brick is largely used in their construction; sometimes they are covered in with a barrel vault, sometimes by two tiles leaning against each other, sometimes by a single flagstone, but in some cases we find the primitive arrangement of projecting courses of stone which was observed above in the drains of Athens.

The expense of cleansing and repairing these cloacae was, of course, very great, and was defrayed partly by the treasury, and partly by an assessment called cloacarium. (Dig. 7, 1, 27.3; 30, 1, 39.5; Marquardt, Röm. Staatsv. ii. p. 146.) Under the republic, the administration of the sewers was entrusted to the censors and aediles; but under the empire, particular officers were appointed for that purpose, cloacarum curatores, mention of whom is found in inscriptions (ap. Grut. p. 197.5, p. 198.2-5; p. cclii. 1, 2). Under the empire condemned criminals were employed in cleansing the cloacae. (Plin. Ep. 10.44 (41).) Theodoric appointed an official to repair the drains, a striking instance of the esteem in which the barbarians held Roman civilisation (Cassiod. l.c.).

On the legal obligations relating to the cloacae at Rome, see Schmidt, Interdicta de cloacis, in Zeitschrift f. gesch. Rechtswiss. 15.1, pp. 51 seq. For further details as to the Roman cloacae, see Burn, Rome and the Campagna; and Middleton, Rome in 1885.

Some traces of the drainage of Pompeii were discovered by Mazois (Ruines de Pompéi, 1.53; 2.36, 99). The extensive remains of the Roman cloacae of Nicomedia are described by Perrot and others, Exploration Arch. de Galatie et Bithynie, 1.2; and by Texier, Descript. de l'Asie Mingure, i. p. 24.

[A.R] [J.H.F]

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