The Period of Archaic Rome
Roman engineers became more daring in the construction of high arches to support the conduits across valleys and plains and some of the later aqueducts were as much as 27 meters (about 100 feet) above ground level in places. Closed pipes were occasionally used to cross valleys by the "inverted syphon" method: the pressure forced the water down and up again on the other side, to a level slightly lower than before. But this system was costly, as it required lead pipes (lead had to be imported from Spain or Great Britain) and it was difficult to make joints strong enough to withstand the pressure; so arches were far more common.
An aqueduct (Lat. aquaeductus) is an artificial channel through which water is conducted to the place where it is used. Most aqueducts of ancient times were built of stone, brick or pozzuolana, a mixture of limestone and volcanic dust. Rome had many aqueducts and was the only ancient city reasonably supplied with water. By A.D. 97, nine aqueducts brought about 85 million gallons of water a day from mountain springs. Later, five others were built. About 200 cities in the Roman colonies had aqueducts.
In Athens, under the rule of Pisistratus (B.C. 560), a similarly extensive, if less difficult, series of works was completed to bring water from the hills Hymettus, Pentelicus, and Parnes. From Hymettus were two conduits passing under the bed of the Ilissus, and most part of the course cut in the rock. Pentelicus, richer in water, supplied another conduit, which can still be traced from the modern village of Chalandri by the air shafts built several feet above the ground, and at a distance apart of 40-50 metres; the diameter of these shafts is 4-5 feet, and the number of them still preserved is about sixty. Tributary channels conveyed into the main stream the waters of the district through which it passed. Outside Athens, those two conduits met in a large reservoir, from which the water distributed by a ramification of underground channels throughout the city. These latter channels vary in form, being partly round, partly square, and generally walled with stone; the chief one, that under the bazaar, is sufficiently high and broad to allow two men to pass in it. Sometimes pipes of baked clay were laid within them. The conduit from Mount Parnes [Parnos] appears to have been reconstructed in later times. Some of these aqueducts continue to supply Athens to this day, and are described as marvels of enterprise and skills (E. Curtius, über die Wasserbauten der Hellenen, in the Archaol. Zeit 1847, p. 19).
In Sicily, the works by which Empedocles, it is said, brought the water into the town of Selinus, are no longer visible; but it is probable that, like those of Syracuse, they consisted chiefly of tunnels and pipes laid under ground. The system of conduits in Syracuse which Thucydides says (vi. 100) the Athenians partly destroyed on the Sicilian expedition, still supplies the town with an abundance of drinkable water; and at one point, where the tunnel passes under the sea to the island of Ortygia, presents what has long been regarded as a remarkable achievement for early times.
An example of what appears to have been the earliest form of aqueduct in Greece has been discovered in the island of Cos [Kos] (Ross, Inselreise, iii. p. 131), beside the fountain Burinna on Mount Oromedon. It consists of a bell-shaped chamber, built underground in the hill side, to receive the water of the spring and keep it cool; a shaft rising from the top of the chamber supplied fresh air. From this reservoir the water was led by a subterranean channel, 35 metres long and 2 metres high. Besides the two principal aqueducts at Rome already described, there remain to be noticed twelve more which assisted in the supply of water for the city. These are:
(1.) AQUA APPIA
(2.) ANIO VETUS
(3.) AQUA MARITA
(4.) AQUA TEPULA
(5.) AQUA JULIA
(6.) AQUA VIRGO
(7.) AQUA CRABRA or DAMNATA
(8.) AQUA ALSIETINA or AUGUSTA
(9.) AQUA TRAJANA
10.) AQUA ALEXANDRINA
(11.) AQUA SEPTIMIANA(12.) AQUA ALGENTINA