For 440 years from the foundation of Rome the inhabitants contented themselves with the waters of the Tiber, and of the wells and fountains in the city and its neighborhood. But at that period the number of houses and inhabitants had so augmented, that they were obliged to bring water from distant sources by means of Aqueducts. Appius commenced this scheme of improvement. About 39 years after him, M. Curius Dentatus, who was censor with Papirius Cursor, brought water from the neighborhood of the city of Tibur ; and applied towards defraying the expense, part of the sums taken in the spoils of Pyrrhus. After them Lucius Papirius, Caius Servillius Cepion, Lucius Longinus Crassus, Q,uintus Marcius, (who brought water to Rome from a spring at the distance of nearly sixty miles,) Marcus Agrippa, Augustus, and others, signalized themselves by their noble Aqueducts. Even Tiberius, Claudius, Caligula, and Carracalla, though in other respects not of the best character, took care of the city in this useful article.

In the remains of these ancient Aqueducts, some are elevated above the ground upon a solid mass of stone work, or upon arches continued and raised one above the other ; other portions are subterraneous, passing through deep excavations, and in many instances piercing through mountains of rock ;

such is that seen at Vicovaro beyond Tivoli, where a tunnel of about five feet deep and four broad, pierces a rock for a distance of more than a mile.

These Aqueducts were generally built of stone and covered by arches or large flat stones. At certain distances