While the ruins of aqueducts and tunnels at Jerusalem, Athens and Carthage give some idea of the skill and knowledge of hydraulic and sanitary matters possessed by the engineers of that period, we must turn to Rome and study their system of water supply, drains for sewage and the ruins of their magnificent baths to form a true conception of the skill of the early school of Roman engineers and the lavish expenditures of treasure by the inhabitants to secure an adequate water supply for Rome. No aqueducts were built in Rome before the year 312 B. C. Prior to that time the inhabitants supplied themselves with water from the Tiber or from wells, cisterns or springs. The first aqueduct was begun by Appius Claudius, the censor, and was named after him the Aqua Appia. This aqueduct had an extreme length of 11 miles, and almost all of the work was entirely under ground. Remains of this work no longer exist. After the Aqua Appia was completed the building of aqueducts seems to have become almost a habit of the Romans, and it was not long—272 B. C.—before M. Aurius Dentatus began a second one called the Anio Vetus, which brought water from the river Anio, a distance of 43 miles. This aqueduct was constructed of stone and the water channel was lined with a thick coat of cement—no doubt Pozzolana cement—made from rock of volcanic origin, which, upon being pulverized and mixed with lime, possessed the hydraulic property of setting under water. Indeed, there can be but little doubt that were it not for this natural cement the construction of Roman aqueducts would have been more difficult to accomplish. [Illustration: Ruins of a Roman Aqueduct] The water furnished by the Anio Vetus was of such poor quality that it was almost unfit for drinking. A further supply being found indispensable, the Senate commissioned Quintus Marcius Rex, the man who had superintended the repairs of the two already built, to undertake a third, which was called after him the Aqua Marcia. This was the most pretentious aqueduct undertaken. It was 61 miles long, about 7 of which were above ground, carried on arches, and of such height that water could be delivered to the loftiest part of Capitoline Mount. A considerable number of the arches of this aqueduct are still standing. Remains are also standing of the Aqueduct Tepula (127 B. C.) and the Aqua Julia (35 B. C.), which, if we except the Herculea branch, are next in point of date. Near the city of Rome the three aqueducts were united in one line of structure, forming three separate water courses, one above another, the lowermost of which formed the channel of the Aqua Marcia and the uppermost that of the Aqua Julia. [Illustration: Distant View of the Claudia Aqueduct]