Page - 168 - in The Power of Urban Water - Studies in premodern urbanism

168 SophieBouffier 180m2, but we are unable tomeasure its capacity in the absence of reliable estimates of the river’s capabilities in ancient times. On the north cliff of the river, the aqueduct’s designers developedacatchmentgallerydugoutof the limestone,of a roughly rectangular shape (height 2.20m,width 0.90m), and towhich a channel arranged at the bottomof the retainment area broughtwater. On the opposite side, a branching structurewith a valve for openingor closing thedamtomaintainthedesiredwater levelandcarryout thenecessarymaintenanceoperations was installed. The routeof theGalermi aqueduct: agoodknowledge of local geology The aqueduct then followed a zig-zag path along the cliff, alongside, first, the Calcinara, then alongside the Anapo, before exiting the gorges of the hinterland to enter the coastal plain. It thus travelledpartly throughthe limestonerocksof theHyblaeanMountains,MountClimitiand the Epipolai plateau of Syracuse. For the remainder, it crossed alluvial and sedimentary loose ground, which suffered landslides, necessitating repairs throughout its history. It was formed inseveralways,dependingon theground itpassed through: it couldbewhollyorpartly rupes- trian; but could also be dug as an open trench and present diverse types of coverage (either semi-circular arches, or horizontal slabs). The aqueduct’s dimensions also vary, depending where it is sited: they are usually the height of aman, around 1.70/1.90m, but can be several metres high, as underMount Climiti, where the channel seems to have exploited a geological fault between two limestone layers. Its width varies from 0.40 to 1.35m. But on average, a sectionhas awidthof 0.70m,with aheight of 1.80m. Thedigging technology At irregular intervals, it is piercedwith inspection shafts: first horizontal, in the cliff of Calcin- ara-Anapo; thesewereopened fromthewatercourse. Theyare locatedat variableheights (from 3 toabout 20m),andhavedimensions ranging from1.45 to 1.65minwidth, from1.20 to 1.50m in height, from 0.80 to 1.50m in depth. In addition to the horizontal inspection shafts, the aqueduct is accessible byvertical inspection shafts,moreor less rectangular (1.40/1.80m), cir- cular or trapezoidal, which differ according to the period, and follow one another at irregular intervals, from25 to 35m indistance (Fig.8). First used todig thegallery, theywere thenused formaintenanceof theaqueduct. In the cliffs of theHyblaeanMountains, inspection shafts are found to be both vertical and horizontal. This dual opening is due to the difficulty in digging theoriginalgallery.Thevertical inspectionshaftwasusedtodirect theorientationof thegallery withdioptra,while thehorizontal inspection shaft allowednot only the evacuationof sizeable quantities ofwastewith the slightest effort, but also ensured the necessary ventilation to pro- videoxygen to themenassigned todigging thegallery. The zig-zag path of the aqueduct testifies to the diggingmethods used by the builders of thestructure (Fig.8). Toassurework teams linked togetherand tonot riskpiercing towards the exterior of the cliff, workers dug from one window to another, always working towards the interior of the rockmass. Theanomalies identified in thegallery attest to thepresenceofmany errors and failures by the teams in linking together that reflect both digging difficulties and differences in the pace of the workers. Many cavities, already found in other aqueducts, are seen in the walls: they housed oil lamps used to illuminate the gallery during its excavation and later, duringmaintenanceof the aqueduct.