The water both of the Anio Vetus and of the Anio Novus was of inferior quality, and was used chiefly for watering gardens, and for the more common purposes in the city; the Anio Novus, being higher than any of the others, and the water very abundant, assisted all the rest. Trajan endeavoured to improve the quality of the water by excluding the more turbid sources, and using only the most pure, as we learn from Frontinus, who was the person charged with the execution of the work[146]; and this inscription was put up, IMPERATOR CAESAR NERVA TRAJANVS AVGVSTVS. The waters of the Claudian and Anio Novus are stated by Frontinus[147] to have been united after their entrance into the city, and then distributed to all the fourteen Regiones. Several subdivisions must therefore have been made at different points, and, wherever a division or a junction took place, a _castellum aquæ_ was required. The union of the two streams was probably made in the large reservoir at the angle of the Sessorian gardens and City wall near the Porta Maggiore. Another great division was over the Arch of Dolabella; one branch was afterwards carried on by Domitian to the Palatine upon the lofty arches, some of which still remain, and into his reservoir at the south-west corner of the Palatine Hill, part of the baths or _thermæ_ of his palace. The branch over the Via Appia to the Piscina Publica and the Aventine was not made until the time of Trajan and Hadrian. A great deal of work was done to the aqueducts at that period. The amazement of the people at seeing copious streams of water pouring over the arid heights and slopes of the Aventine, is recorded by a contemporary author. This was the branch of which a portion remains near Santa Prisca. The branch from the Palatine to the Capitol, of which two of the tall piers remain[148], was made by Caligula; this is sometimes called a bridge across the Forum. To convey the water to the other Regiones, the older conduits or _specus_ were probably used. 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].