In the fourth century, there were great complaints of the stealing of the Aqua Claudia by the farmers through whose lands it passed, and several strenuous decrees against this practice were issued by the Emperors Arcadius and Honorius, A.D. 400. Similar edicts were issued repeatedly by these Emperors, and by Constantine[149].
The springs called Cæruleus and Curtius, to which (when united in this aqueduct) the name of Claudia[150] was given, as Frontinus tells us, are situated in a valley on the south side of the river Anio, thirty-eight miles from Rome, and eight miles below Subiaco (which is forty-six miles from Rome), and not more than half a mile from the source of the Marcia. Several streams issue from the rock under the present carriage-road, a diverticulum or branch of the ancient Via Valeria, and form a beautiful small lake of very clear water having a distinctly bluish tint. Another of these springs, the Albudinus, is still considered as equally good with the Marcia, or nearly so. The Anio here flows at the opposite end of this small valley, and both the lakes are now emptied into it. This valley is in the territory of Arsoli, so called from a neighbouring village on a height overlooking it, and the lake of S. Lucia. The spring called Curtius is another of these streams.
This valley is admirably calculated for the sources of aqueducts; the ground is full of springs of beautiful water, and the watery meadows have only to be dammed up a little to form lakes or reservoirs. Probably the water from these springs, which now runs into the river, was entirely intercepted and carried into Rome in the aqueducts. The Anio is in general such an abundant stream, that these additional springs would scarcely be missed, although in time of severe drought the water did sometimes run short[151].
The piscinæ, mentioned by Frontinus, were large subterranean reservoirs and filtering-places, at seven miles from the old City or from the inner gates, and six from the outer gates: the portion of Rome outside of the walls of the city was considered as the suburbs only, until the time of Aurelian, when the City was made to extend to the outer wall, then newly raised and fortified, but this was long after the aqueducts were made. The present appearance of these two piscinæ of the Claudia and the Anio Novus is merely that of earthen mounds or tumuli. They are situated about midway between the old Via Latina, which now in this part is made into a carriage-road to Frascati, and the Via Appia Nova. The distance from one road to the other is about a mile, and the piscinæ are about half-a-mile from each. The stream, which was originally a branch of the Almo, and now conveys the water of the Marrana and the Aqua Crabra united, runs near them, and received the surplus water from all the aqueducts on this line. It is divided into two parts near the piscinæ, one branch going through the valley called the Caffarella, and falling into the Tiber near the church of S. Paul’s outside of the walls; the other keeps near the arcades and reservoirs, and coming through Rome, passes on the south side of the Cœlian. This branch had come from the piscinæ nearly parallel to the aqueducts; it winds about a good deal, but is never distant from the line of the latter, now on one side and then on the other. A further account of this will be found under the head of the Marrana, in the second part of this chapter.
APPENDIX TO CHAPTER IV. PART I.
THE NINE AQUEDUCTS IN THE TIME OF FRONTINUS.
Having sketched the general history of each one of these aqueducts, and the circumstances under which they were erected, it remains to refer briefly to some of those details which Frontinus has handed down to us, of the mode of management of the water. These details apply equally to the whole series. First of all, the position which he and his predecessors in office held was a very important and honourable one. He had the entire responsibility of the water supply, and the absolute control of seven hundred men employed to attend to their proper working, to clean the piscinæ, and to repair the channels and pipes when needed. Of these, 240 were appointed by the City, and the remaining 460 by the Emperor. The channels in which the main stream of water was carried, and the reservoirs (castella), and the piscinæ, were always lined with a particular kind of cement, called Opus Signinum.
It has also been observed that the base of the channel is constantly broken up by inequalities, or dips, if they may be termed so, as if purposely introduced to agitate the water in its course, and, consequently, to aërate it. No doubt also the inequalities, provided they were rugged, would tend to check the passage of any earthen matter held in solution by the water. Of most importance, however, and shewing still more remarkably the engineering qualities of the builders of the Aqueducts, were the ventilating-shafts which were introduced at proper intervals. Such shafts were often used as wells also, to let buckets down for water, and steps were cut on the sides for the aquarii to descend and remove obstructions. At about every half-mile the specus forms an angle to break the force of the water, and at such points there is usually a reservoir also. Advantage was taken of these angles for the later aqueducts to be carried over the older ones, as at the Torre Fiscale and the Porta Maggiore. These precautions, combined with the system of Piscinæ, rendered the water constantly fresh, pure, and wholesome.
From some considerable remains of the Piscinæ, the system can be clearly made out. The building consisted of four chambers, two beneath and two above. Supposing, for the sake of illustration, in the annexed diagram, the letters