C. Two streams coming out of a sort of double cave, and meeting at the mouth of it, from whence they are carried across the meadow in a specus open at the top for a certain distance, and having the appearance of a ditch only; but the water from this spring also never fails, and these two streams united gave a certain steady supply to the aqueduct. The meadow through which these streams flow has a clay soil, and the water is always liable to be muddy after rain, and left a large deposit of clay in the specus, as is shewn in other plates.
THE AQUEDUCTS.
PLATE XVIII.
AQUA APPIA, OR APPIAN AQUEDUCT.
XVIII.
THE APPIAN AQUEDUCT PASSING OVER THE PORTA CAPENA AND THROUGH THE TOWER.
Description of Plate XVIII.
AQUA APPIA, OR APPIAN AQUEDUCT.
Crossing the valley from the Cœlian to the Aventine upon the agger of Servius Tullius and over the Porta Capena, this was the only part that was above ground, as we are told by Frontinus[234]. In this view the pavement of the Via Appia is seen in the foreground, then the wall of Servius Tullius, twelve feet thick, (as usual with the walls of the Kings;) by the side of this, to the left, is seen the arcade that carried the specus of the aqueduct; this goes as far as the branch of the river Almo (now called the Marrana), which runs through the valley. On the further side of the stream the land is high, and the aqueduct is again underground, but it has been traced not only across the valley, but under the cliff on the northern side of the Pseudo-Aventine, with a branch to the left to supply the Piscina Publica, which was an enormous swimming-bath for the whole population of Rome at that period, extending as far as the north end of the Thermæ of Caracalla, where the hollow with the bank round it can still be seen, and where a great reservoir remains, lined with the cement called opus signinum (or coccio pisto). The ruins of another great reservoir rebuilt in the time of Trajan are at the north-west corner, nearly under the Aventine, and are called the Piscina Publica.