Roman Building 518
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Roman building 518 583 Detail of a lead pipe supplying the baths of Julia Felix at Pompeii. The lengthways soldering can be seen, which seals the cylinder made of a rolled-up sheet of lead, and the circular soldering (left) which bonded it to the next pipe. 584 Just like ceramic products, lead pipes, particularly those with a large diameter, could be given a stamp indicating the monument they were intended for, the owner, the Civil engineering 519 manufacturer and, in the case of the aqueducts of Rome, the name of the emperor: Imp(eratoris) 585 Two sections of lead pipes with a large diameter, in the Museo Nazionale delle Terme in Rome. Two of them are complete and have preserved a part of the soldered rim connecting them to their neighbours. Length: 2.6m; vertical diameter: 25cm; horizontal diameter: 22cm. From Castel Porziano. 586 Stamp of Marcus Aurelius (139– 61) on a pipe. Roman building 520 587 Pipes made of terracotta tubes jointed and sealed with lime mortar at Ephesus. Caes(aris) Traj(ani) Hadriani Aug(usti) sub cura Petronii Surae proc(uratoris); Martialis ser(vus) fe(cit).60 It is curious to see here, running contrary to the segregation of slavery, that equality was re-established in a manufacturing mark which brought together the name of the all-powerful emperor, that of the aedile and that of the slave- manufacturer of the product. Lead pipes of the urban water system at Pompeii were more simple and carried a mark showing where they belonged: (usibis) publ(icis) Pompe(ianorum). Lead had only one disadvantage, but one which was particularly restrictive for modest provincial municipalities—its rather high cost. The raw material itself was difficult to obtain61 and its preparation required a highly-skilled workforce; this is why it was replaced by other materials, principally ceramic pipes. These tubes had a constriction at one end for fitting into one another; they usually had a large diameter, 13 to 20cm, and were 45 to 70cm long. The connections were made watertight by lime mortar, which Vitruvius recommended should be kneaded with oil to increase its impermeability (VIII, 6) (fig. 587). The author of the Ten Books was also distrustful of lead piping, which he accused of poisoning the water (wrongly in fact),62 confusing it with white lead (cerussa), a carbonate of lead used as a white pigment, which is in fact a dangerous poison.63 In wooded areas it was still more economical to use wood to make pipes. Not only could channels be carved from half-logs, but proper pipes were made by hollowing out Civil engineering 521 straight trunks using drills with a very long bit, in all probability identical to those used by ‘well-sinkers’ of mountainous regions right up until the twentieth century. The junctions between two wooden pipes were made by leather collars or metal pieces, the whole thing possibly being contained in a drilled block of stone and enclosed in a guttering lined with clay. An installation of this type has been found in the supply to the monumental fountain at Argentomagus (St-Marcel, Indre)64 (fig. 588). Returning now to Pompeii to follow the progress of the piping: from the main water distribution centre pipes radiated out, buried approximately 60cm under the pavements, then entered a series of secondary water towers intended to break the pressure caused by the significant change in level (figs 589, 590, 591). The principle adopted was that of stepped siphons, i.e. the same as that of the levels created to break the impetus of the torrents. The need to keep the water in watertight pipes forced the hydraulic engineers to install a series of masonry columns along the course of each branch emanating from the water distribution centre. These contained rising and falling pipes and supported a lead tank, the castellum plumbeum, at the top, in which the water lost its pressure before being distributed into the urban supply. The first column, placed 139m from the front of the castellum, was already 7m lower, and the builders, who were not very accurate in their levelling, built it to more or less the same height; probably realizing their 588 The monumental fountain at Argentomagus (St-Marcel, Indre). The four pillars in the basin supported a roof. The supply, at least in its final state, arrived via a wooden pipe under the steps. Roman building 522 589 A secondary water-tower of the supply network at Pompeii (VI, 16) (height: 7m). At the top of the masonry pillar was a lead tank with a lid, supplied by pipes housed in a groove on the upstream side; the outflow pipes were located in the groove downstream (visible in the photo) and then went under the pavement; one of them supplied the fountain. Civil engineering 523 590 The Arch of Caligula at one end of the via di Mercurio at Pompeii. The structure served as a secondary water- tower, the lead pipes being housed in conduits made in the masonry piers. Two fountains, demolished in 62, were located at the foot of it. mistake, they gave a greater discharge to the other pillars. Thirteen of them65 have been found distributed over the whole city, each one having a height such that the water arrived at its base at a pressure between 1.5 to 2 kg/cm2. In order to allow maintenance of the system, taps, above the distribution points, made it possible to interrupt the current, while the different basins, reservoirs and fountains were provided with a means of drainage. In view of the division into three of the castellum at Pompeii, it is tempting to presume a distribution of water conforming to the recommendation made Roman building 524 591 Secondary water-tower in the Forum Baths at Pompeii, incorporated into the external wall of the building in the course of the developments in the Julio-Claudian period. 592 The communal latrines were constant consumers of water and formed part of the developments of public spaces, as at the forica of the Forum Baths at Ostia. A flow of water Civil engineering 525 circulated under the seats at the bottom of the peripheral ditch. A fountain on the right-hand wall catered for ablutions and allowed a flow of water to run into the gutters of the paving. by Vitruvius (VIII, 6). He advocated, for fairness, dividing the castellum into three basins situated at different levels (or one single basin with pipes staggered in height coming out of it), with three destinations: 1 A level that was permanently supplied, even in the dry season, providing water for the domestic use of private individuals (fountains and houses). 2 A middle level supplying public monuments (baths). 3 An upper level, the first to be cut off in the event of a lowering of water level, leading to fountains or basins and to water spouts 593 Fountain of a domus, with a mosaic and shell decoration at the House of the Large Fountain, Pompeii (VI, 8, 22). These small structures were connected to the public main. Roman building 526 594 The large nymphaeum of the villa of the Quintilii, on the via Appia between Rome and Bovillae, built in the third century AD. The large apse containing the basin was covered over with a half-dome. The right-hand part of the structure is concealed by a medieval construction; a special aqueduct, as at the Villa dei Sette Bassi, supplied the building. (lacus et salientes)66 (figs 592, 593, 594). This automatic distribution, itself varying with changes of level, could have been replaced by a sluice-gate system maintained by the municipality, but it is possible that the reliability of the supply did not make such a precaution necessary and there is no conclusive evidence surviving to be certain whether Pompeii did or did not ration its supply. Whatever the case, it was the public fountains that got the largest share of the water from the urban supply since forty have been found, almost all intact, over the uncovered three-fifths of the city. They were distributed as evenly as possible so that they were a distance of 70 to 80m apart; the people of the neighbourhood thus always had access to water less than 40m from their homes. The appearance of these fountains does not vary very much: a rectangular trough built half across the pavement, half across the roadway, made up of four dressed slabs, almost always lava67 held together by iron cramps sealed with lead (figs 595, 596). The water came through a lead pipe rising from inside a stone placed on the pavement side, and ran into the trough through a sculpted motif. These motifs always differed from one fountain to another (fig. 597). Vertical water-proofing was ensured by a fixed string- Civil engineering 527 course of pink mortar, poured into a channel dug into the joint between each slab (fig. 598). 595 A public fountain at Pompeii, decorated with a head of Mercury. The supply pipe came out of the figure’s mouth. The overflow channel is visible on the top of the rim, and, at a lower level, the outflow of the drainage hole VI, 8. Roman building 528 596 Cross-section and plan of a public fountain at Pompeii (via di Stabia, VII, 1). Civil engineering 529 597 Pompeii: a fountain on the Via dell’Abbondanza (VII, 14). As the back edge stone has disappeared, the hole through which the supply pipe passed is visible. 598 Detail of the jointing of two dressed stone slabs in the trough of a public fountain at Pompeii, showing the channel into which was poured the string-course of mortar for Roman building 530 waterproofing and the sealant for an iron clamp (IX, 9) 599 Basin of a public fountain at Pompeii (at the crossroads of the via dell’Abbondanza and the via di Stabia) showing the lining covering the bottom, placed on bricks, and the watertight edging round the sides.