Little search has been made for the remains of this aqueduct, and its exact course is not known; but during my examination of the remains of the subsequent aqueducts at a place called the Porta Furba, near Rome, where the ruins of five aqueducts are seen together, and at, or close to, which point the Anio Vetus must also have passed underground, I was rewarded for my search by discovering a hole, something like a fox's hole, leading into the ground; and on clearing away a few loose stones which had apparently been thrown into it, and putting my arm in, I found that it led into the specus or channel of an underground aqueduct; and on relating this incident to the late Mr. John Henry Parker, the antiquarian, who was then in Rome, and showing him a sketch of the place, he said that he had no doubt that I had been fortunate enough to discover the exact position of the veritable Anio Vetus at that spot. These two aqueducts sufficed for the supply of Rome with water for about 120 years, for Frontinus tells us that 127 years after the date at which the construction of the Anio Vetus was undertaken--that is to say, the 608th year after the foundation of the city--the increase of the city necessitated a more ample supply of water, and it was determined to bring it from a still greater distance. It was no longer considered necessary to conceal the aqueduct underground during the whole of its course, and so it was in part carried above ground on embankments or supported upon arches of masonry. The water was brought from some pools in one of the valleys on the eastern side of the Anio, some miles farther up than the point from which the Anio Vetus was supplied; and the new aqueduct, which was 54 miles in length, was called the Marcian, after the Prætor Marcius, to whom the work was intrusted. Frontinus also tells us the history of the other six aqueducts which were in existence in his time, viz., the Tepulan, the Julian, the Virgo, the Alsietine or Augustan, the Claudian, and the Anio Novus; the last two being commenced by the Emperor Caligula, and finished by Claudius, because "seven aqueducts seemed scarcely sufficient for public purposes and private amusements;" but it is not necessary for our purpose to give any detailed account of the course of these aqueducts; it is only necessary to mention one or two very interesting points in connection with them. In order to allow of the deposit of suspended matters, piscinæ, or settling reservoirs, were constructed in a very ingenious manner. Each had four compartments, two upper and two lower; the water was conducted into one of the upper compartments, and from this passed, probably by what we should call a standing waste or overflow pipe, into the one below; from this it passed (probably through a grating) into the third compartment at the same level, and thence rose through a hole in the roof of this compartment into the fourth, which was above it, and in which the water, of course,