When the news of this act of profanation arrived in the city it created a great sensation; and an illness with which he was shortly afterwards seized was attributed to the anger of the god.
Seven miles lower down on the right, the Tiber receives the Nestore, a large and impetuous torrent, or _torrentaccio_, as it is called by the Italians. The Nestore, where it enters the Tiber flows in a bed of sand and shingle no less than a third of a Roman mile in width, and after heavy rains must bring down an enormous body of water. Into the Cina, one of its tributaries, by means of a tunnel, the overflow of the lake of Thrasymene is discharged. The emissary originates in the south-eastern bay of the lake, but when, or by whom, the work was executed is a matter of dispute. Thirty and a half miles further on, the Tiber is joined by the Chiana (anciently Clanis), which, after uniting with the Paglia, flows into it on the same side as the Nestore and in the neighbourhood of Orvieto.
The Paglia rises in the high volcanic mountain of Monte Amiata, and in summer is nearly dry; but its broad stony channel at Acquapendente shows what a contribution it must bring to the main stream in time of floods. The Chiana, which from the black and muddy colour of its waters has received the name of the Lethe of Tuscany, but which might with more propriety be called the Tuscan Cocytus, was once a single stream originating in the neighbourhood of Arezzo, and flowing southward into the Tiber. But in the Middle Ages a large portion of the valley in which it flowed was filled up by the _débris_ which in time of floods was brought down by the lateral torrents. A sort of plateau was thus formed, sloping at its edges towards the valleys of the Tiber and the Arno. The streams which entered this plateau stagnated in the level which it formed, converting it into an unproductive and unhealthy marsh, the abode of malaria and the pest-house of Dante’s _Purgatorio_. They then flowed over the northern and southern edges of the plateau, and, uniting with others, formed two distinct rivers called the Tuscan and Roman Chianas.
The torrent of the Tresa, rising not far from the lake of Thrasymene, and now diverted into the lake of Chiusi, may be considered as the head waters of the Tuscan Chiana, the torrent of the Astrone, rising in the direction of Montepulciano, as the main branch of the Roman Chiana. The two are connected by canals and wet ditches, so that it is conceivable that a small piece of wood thrown into one of these might, according to circumstances and the direction of the wind, find its way to Florence or to Rome.
The district which I have described, the celebrated Val di Chiana, is now one of the most productive regions of Italy, green with vineyards and pastures, and golden with waving crops. Nor is it unhealthy, except in the immediate vicinity of the lakes. The change was effected by canalizing the streams, and by the process called warping, which is the method adopted in Lincolnshire for reclaiming land from the sea. A certain space was enclosed with banks, into which the streams were diverted when they were swollen and charged with mud. The opening was then closed with a floodgate, and the water left to deposit the matter which it held in suspension. In this way an inch or two of soil was gained every year, until the land became sufficiently dry and firm. It was then sown with crops, and planted with trees, which served still further to purify the air by decomposing with their leaves and fixing in their tissues the vapours which had given the Val di Chiana so deadly a name.
Turning again to the south-east and at a distance of 136½ miles from its source, the Tiber is swelled by the united streams of the Neva, the Velino, and the Salto. The Neva, the “_sulphurea Nar albus aqua_” of Virgil, and “_Narque albescentibus undis_” of Silius Italicus, rises at the foot of the lofty peak of Monte Vettore, part of the Sibylline range, and is the tributary which is most affected by the melting of the snows.
The Velino also has its source in the great central chain of the Apennines, and after being joined by the Salto and Turano, forms the cascade of Terni by dashing over the precipice which terminates the valley, and hastens to meet the Neva. The Salto, rising in the kingdom of Naples, flows northward for fifty miles, and after passing beneath the lofty range of Monte Velino, and receiving a contribution from its snows, mingles its waters with the Velino. Swelled by these tributaries the Neva rolls along a full and rapid stream, and sweeping past Terni and Narni, loses itself in the Tiber.
About sixty-four miles lower down, and four and a half above Rome by the river, the Tiber is joined by the Anio, or Teverone, the most important, with the exception of the Neva, of all its tributaries. No river is better known than the Anio. The scenery of its valley, the classical associations of its neighbourhood, and the celebrated cascades of Tivoli, have made it the favourite resort of tourists. The Anio rises in the mountains of the Hernici, part of the modern Abruzzi, and after flowing for about thirty-six miles through a narrow valley whose general course is to the west, precipitates itself into the gorge which is overlooked by the town of Tivoli; emerging from which it turns west-south-west and joins the Tiber, after a further course of twenty miles. Midway between its source and Tivoli, it passes the town of Subiaco, anciently Sublaqueum, which derives its name from three picturesque lakes, “_tres lacus amœnitate nobilis_.” Tivoli is well known to have been the favourite retreat of the wealthy Romans from the turmoil, and what Horace calls the “fumus,” of Rome. The names and ruins of these villas yet remain, but no trace is left of those which once adorned the banks of the Tiber, and perhaps of the Anio in the lower part of its course.
Pliny the younger calls the Anio “_delicatissimus amnium_,” “softest and gentlest of rivers”; and adds “that it was for this reason invited, as it were, and retained by the neighbouring villas” for their own exclusive use. Yet, this “delicate river” indulged occasionally in the wildest escapades, and Pliny himself, in this very letter, describes an inundation in which it swept away woods, undermined hills, and committed extraordinary havoc among the neighbouring farms. From this time to the year 1826 it was a source of apprehension to the people of Tivoli, and an anxiety to the government at Rome, which expended considerable sums in trying to prevent some great calamity, or in repairing the damage which had been done. Once since the time of Strabo the river is thought to have changed its course, discharging itself at a lower level into the Grotto of Neptune, but still forming a lofty and picturesque cascade.
At different periods it had destroyed buildings, undermined the foundation of others, and defied every effort to control its violence. At length these floods culminated in the great inundation of 1826, which entirely altered the character of the cascade, and necessitated the formation of the tunnel through Monte Catillo.
The work was let on contract to two rival firms, and pushed forward with such vigour that, though it was considered a most arduous undertaking in those times, it was completed in 1836, during the Pontificate of Gregory XVI.
From the Anio, or its tributaries, was drawn the water which supplied the principal aqueducts of Rome, the Anio Vetus, the Marcia, the Anio Novus, and the Claudia. When the original Aqua Appia and Anio Vetus were found insufficient for the increasing wants of Rome, it was resolved to seek for a fresh supply. This was found in a stream of limpid water rising about thirty-six miles from Rome in the Marsian Mountains, and flowing into the Anio. As the water of the Vetus was often turbid after rain, and even the Piscina, or reservoir, through which it was made to pass, often failed to purify it, Quintus Marcius Rex, who was appointed to superintend the work, was desirous that the water of the new aqueduct should be taken from one of the tributaries of the river, and as near as possible to its source.
As the source was in the country beyond the Anio, the aqueduct was of course more expensive than any of the preceding ones, and the entire length of it was no less than sixty-one miles, of which several were on arches, the rest being subterranean. But, if the expense was greater, the quality of the water was superior to that of any other with which Rome was acquainted.
The aqueducts of the Anio Novus, and the Aqua Claudia, of which I have spoken, were completed in the reign of Claudius. The Aqua Claudia, which came from springs, was nearly equal in quality to the Marcia, while the two Anios were often turbid, even in fine weather, from the falling in of their banks. But Claudius improved the quality of the Anio Novus, by abandoning the river at the point from which the water had been drawn, and taking it from a lake, out of which the stream issues limpid, after having deposited the greater part of its impurities.