Aqua Virgo is near the eighth milestone, only 80 feet above sea-level; its channel was 14 miles long, and it entered the city 13 feet lower. The channel was about 1.6 feet wide and 6.6 feet high. It still supplies the famous Trevi foun- tain and others.
(7) Aqua Alsietina, about A.D. 10, constructed by Augustus, now called the Aqua Paola, starts at a pond near the fourteenth milestone, and sup- plies the fountains in front of St. Peter's and the Fontana Paola, on the Montorio. Its original object was for irrigating purposes, and to supply the Nauniachia of Augustus, which was a sheet of water for the representation of sea fights. Its water, which was undrinkable, reached Rome in a channel 24 miles long, about 55 feet above the sea, the lowest level of any.
(8) Aqua Claudia, A.D. 38-52, commenced by Caligula and completed by Claudius, starts near the thirty-eighth milestone and is about 45 miles long. Its line of nearly ten miles of magnificent arches still stretches across the Campagna, and forms one of the grandest of Roman ruins. At its upper end its channel was 3.3 feet wide and 6.6 feet high. When it reaches the Campagna it carries the Anio Novus (see below), the lower aqueduct being of dimension stone and the upper of brick, lined with concrete. The water of these two aqueducts reached the Palatine 185 feet above the sea; but at Porta Maggiore the water in Anio Novus was at an elevation of 230 feet and Claudia 9 feet lower.
(9) Anio Novus, also A.D. 38-52, was nearly 62 miles long, thus being the longest of the aqueducts, and starting at the Anio, near the thirty-eighth milestone. Its channel had a width of 3.3 feet and a height of 9 feet. Some of its arches are over 100 feet high, and its ruins are as superb as those of the Claudia, the two combining before entering Rome.
Aqua Trajana, built in A.D. 109, started at Lake Bracciano, was about 40 miles long, followed nearly the same route as Aqua Alsietina and its waters join to form the supply of the present Aqua Paola. It was used for supplying the Janiculum and the Trastevere. In A.D. 226 an eleventh and last aqueduct was built, called Aqua Alexandrina, to supply the Campus Martius. The other aqueducts sometimes credited to old Rome were probably branches of some of the eleven.
Although stone continued in use for aqueducts under the Empire, concrete with opus rerticulatum and concrete with brick were used both in various parts of Italy and even in Rome itself, especially in the Aqua Alexandrina and Nero's additions to the Claudia. There remain many imposing Roman aqueducts in different parts of the Empire. The high viaducts and bridges in France, such as those near Nîmes, Cahors, and Lyons; in Spain at Segovia, Mérida, and Tarragona: at Constantinople, at Beirut, at Cherchel and Carthage are especially imposing — higher and bolder than anything at Rome; some have two, some three superposed stories of arcades, with a total height of between 100 and 300 feet. The Pont du Gard and the aqueduct of Segovia are the finest in existence. The stonework in the provinces is even superior to the average in Rome. The following examples may be mentioned: Italy: Minturnæ (fine opus reticulatum, very decorative), Genoa (very early, c .210 B.C.), Puteoli, Pompeii, Termini in Sicily. Gaul: Nîmes (Pont du Gard), Lyons (4 aqueducts in opus reticulatum, with siphons and bridges), Metz (with a great bridge of 114 arches), Paris (3 aqueducts of late Roman date), Frejus (a superb example, built under Claudius, 30 miles long, with many arcades), Antibes (2 aqueducts, one still in use), Arles, Marseilles, Aix, Vienne, Autun, Besançon, Poitiers (4), Cahors (a superb three-storied viaduct), Toulouse, and many others. Germany: Mainz, Treves, Cologne, Solicinium, Windisch. Spain: Segovia (built under Trajan. 12 miles long, with a superb viaduct of 119 arcades, 818 yards long, in two stories), Tarragona (built in the Republican Period, c. 210 B.C., 6 miles long, with magnificent two-storied viaduct of 11 and 25 arches), Chelva, Seville, Mérida (2 aqueducts, one still in use; the other by Augustus, with a viaduct of three stories), Consuegra, Calahorra. Portugal: Elvas, Evora, Beja. Africa: Tebessa, Constantine (3), Tipasa, Cherchel (Cæsarea), Orléansville, Carthage (Punic and Roman), Makter (with a viaduct). Asia: Anazarba. Beirut (with a bridge). Palmyra, Baalbek. Petra, Sinope, Xicomedia, Antioch, etc.
The Oriental provinces of the Empire, preserving Greek engineering traditions, were more scientific, as shown by frequent use of siphons. The Byzantine emperors continued the Roman traditions, as shown by the aqueducts of Valens and Justinian at Constantinople, in connection with which are the wonderful cistern-reservoirs in the city with their forests of columns. Adana, Mopsuestia, and many other Eastern cities were provided by Justinian with aqueducts. The Gothic kings attempted the same, as in the extremely bold viaduct at Spoleto, loftier than any Roman work; their work in Spain was continued by the Moors, as at Elvas. The Mohammedans throughout the East continued the construction of aqueducts; but the Middle Ages in Europe were comparatively inactive in this branch of engineering. The Gothic aqueduct at Solmona and that at Coutances are perhaps the finest in Europe of this age. The Renaissance renewed the art, beginning with the Roman popes of the Sixteenth Century. France soon followed suit, as in the aqueduct of Arceuil at Paris built for Marie de Medici in 1613, and that of Maintenon under Louis XIV. In 1753 Charles III. built the great aqueduct of Caserta, about 30 miles long. The aqueduct of Marseilles, begun in 1847 and over 40 miles long, with 75 tunnels and several viaducts, is the only work of modern engineering construction comparable artistically to the Roman; it could have been built for a fraction of the cost ($1,200,000) by using siphons.
Among the European aqueducts constructed during the latter part of the Nineteenth Century may be mentioned, first, that conveying water from Loch Katrine to Glasgow, built in 1855-60 and duplicated quite recently. The new water-supply conduits of Manchester and Liverpool, built in 1881-92 and 1885-94, respectively, are partly masonry structures and partly pipe lines. The Liverpool supply is brought from Lake Vyrnwy, a distance of 68 miles, partly in tunnel. The Manchester supply comes from Lake Thirlmere, a distance of nearly 96 miles, through 36 miles of concrete conduit and 14½ miles of tunnel, making 50½ miles of masonry aqueduct, and through 45 miles of iron pipe. The largest
