AQUEDUCTS. Aqueducts are artificial channels and structures connected therewith, for conveying water from one point to an other. In a broad sense the word is generic, applying to all such channels or structures, but it is now generally restricted to elevated struc tures or tunnels designed to convey water by gravity for municipal water supply, though it is not infrequently used in connection with ir rigation, water power and other hydraulic de velopments.
Water being a prime necessity for the sup port of both animal and vegetable life, it is not surprising that devices and means for supplying it in large quantities for domestic use in cities and for irrigation purposes attracted the. early attention of mankind. Their construction and use dates far back of the historical period, and they were doubtless among the earliest and most important engineering undertakings of ancient times. The ruins of these early canals and water-supply works are found in Phoenicia, Babylonia, Assyria, Egypt, Persia and Pales tine. Some of them were of such magnitude and designed and constructed with such bold ness and skill as to excite the wonder and ad miration of the modern world.
Ancient Aqueducts.— The Phoenicians were especially notable for the character, extent and boldness of their hydraulic works and, consider ing the means at their command, it is surprising what they accomplished.
At a later period Greece and Rome became famous for their water-supply projects and the building of great aqueducts. In Greece, early examples of tunnel constructions for water supply were quite common, some of them being of comparatively great length and, at places, more than 100 feet below the surface. One such tunnel at Samos was four-fifths of a mile long, the interior dimensions being 8x8 feet- the water conduit proper being an independent stone trough. Athens was supplied by several aqueducts, built from time to time as the city grew and a larger water supply became needed. One of these, begun some 600 years s.c., under the Emperor Hadrian, is still in use.
Rome was supplied with water by about a dozen aqueducts built at different periods, nine of which are commonly referred to by writers as the more important. The first, the Aqua
Appia, was built about 300 years B.C. It was about 11 Roman miles long and almost wholly underground. Among the latest of the nine to be built were the Aqua Claudia and the Anio Novus, completed in the first half century of the Christian era.
Some of these aqueducts would be consid ered as stupendous undertakings in modern times. Thus the second one built, the Anio Vetus, was more than 40 miles long, mostly in tunnel. The Aqua Marcia, built about 140 ac., was 60 miles long, about six miles of which were above ground, carried on masonry arches.
The Aqua Tepula, some 11 miles long, was carried for more than half the distance on a second series of arches, superimposed upon those of the Aqua Marcia. The Aqua Augusta was 22 miles long, of which something over 1,000 feet were carried on masonry arches. The Anio Novus, 62 miles long, was carried across the Campagna for more than nine miles by a series of masonry arches, part of which still remains a conspicuous feature of Roman scenery. The water channel carried above the arches was from three to four feet wide and nine feet high, the inside being lined with Roman cement.
Not only at Rome, but in many places throughout the empire did the Romans build great aqueducts. Among the most noted of these may be mentioned those at Servigonia, Italy; Segovia and Tarragona, Spain; Metz in Alsace-Lorraine; Carthage, Constantinople, and Nimes in France. The latter, now known as the Pont du Gard, is a magnificent structure across the river Gardon, built in the 4th cen tury A.D. It has three tiers (or stories) of masonry arches, one above the other. The lower tier has one arch (over the river), of 75 feet span and five others of 60 feet span. The third or uppermost tier is made up of a series of smaller arches, in all 873 feet long, the greatest height over the river being 188 feet. The masonry water conduit, covered by flat stones and lined with cement; is about four feet wide and four and one-half feet high. This grand structure, still standing in a good state of preservation, compares favorably in its en gineering and architectural features with any similar work of modern times.