Within the last few years a large leaden pipe of great antiquity, not less than two feet in diameter, was found under the Via de’ Condotti, encased in ancient brickwork, evidently shewing that they were afraid to trust to the strength of the lead. The force of the water running in a strong current from such great distances, required to be broken at frequent intervals, by being turned at a sharp angle, and then allowed to return again to its course by another angle. This arrangement occurs continually along the line of the aqueducts, generally at each half mile, with a _piscina_ or a _castellum_, or both filtering-place and reservoir, at each of these angles. The great object of constructing these magnificent aqueducts was to bring the water to the highest levels in the city, from which it descended by a succession of reservoirs (_castella aquarum_), some with _piscinæ_ or filters, others with fountains, each one below the level of the preceding one. The lower town along the valley, or Campus Martius, was also supplied by other aqueducts at a much lower level. The ancient Romans had abundance of leaden pipes to convey the water to the baths or _thermæ_, and bronze stop-cocks, as may be seen at Pompeii, and silver ones for the emperor; but they had no pumps. From each _castellum_ there were pipes to supply the neighbouring baths or palaces, with moderate pressure; also wells or cisterns in the courtyard of each house, which had frequently a fountain. On the Janiculum, the water of the aqueduct passing from one _castellum_ to another, has sufficient force to turn several mill-wheels. A letter of King Theodoric, printed in Cassiodorus[167], addressed to the Roman Senate, enjoins them to assist Joannes in his enquiries after those who have diverted the water from the aqueducts for their own uses, and those who have stolen the brass and lead, or those who have helped them. This proves that they were not destroyed by the Goths, and that they were in use in the sixth century. CHAPTER IV., PART II. THE LATER AQUEDUCTS. X. SABATINA, A.D. 110; TRAJANA AND PAOLA, A.D. 1540. The Aqua Sabatina came from the springs which supply the lake Sabatinus, now called di Bracciano (in the Middle Ages it was, and is still often called, Anguillara), on the side opposite to Rome, about twenty-four miles from the city, in a tunnel at a considerable depth. It arrives at the line of the tunnel of the Aqua Alsietina in about three miles. (See Aqueduct VII.)