CHAPTER XI.

THE WATERWAYS OF ITALY. “Though Tiber’s streams immortal Rome behold, Though foaming Hermus swells with tides of gold, From Heaven itself, though sevenfold Nilus flows, And harvests on a hundred realms bestows, These now no more shall be the Muse’s themes, Lost in my fame as in the sea their streams.” —_Pope._ There is no characteristic of the ancient Roman Empire that is more striking at the present day, after the lapse of nearly twenty centuries, than the proficiency that the people had attained in the arts and sciences, and more especially in the arts of architecture and engineering. The aqueducts which they built for the supply of water for domestic purposes were vast structures that have hardly been equalled in any subsequent period, and the canals which they constructed for the drainage of morasses, or the transport of armies, were hardly less remarkable. _Early Canals._—Among the earlier navigation works, perhaps the most remarkable was the canal which the Romans constructed for the drainage of Lake Fucino, illustrated on p. 154. This canal, which was commenced by order of the Emperor Claudius, is said by Pliny to have occupied 30,000 men for ten years. The lake is surrounded by a high ridge of mountains called Celano, which are stated to be nearly fifty miles in circuit. The passage of the waters from the lake into the canal was witnessed by a vast number of persons, when the undertaking was completed, but the canal was not sufficiently deep to allow the water from the lower part of the lake to drain off, and although it was sought to correct this defect in Nero’s reign, the project was never really finished. As far as it went, the work is described by Tacitus,[94] while Virgil speaks of the lake—now no longer covered with water—as well known.[95] Hydraulic engineering formed so important a part of the business of the ancient Romans that the pro-consuls were charged to lay before the emperors the best methods of changing the course of rivers, for the purpose of facilitating the approaches from the sea to the centres of the various provinces. Thus, we find that Lucius Verus, General of the Roman army in Gaul, undertook to unite the Saône and the Moselle by a canal. He is also said to have undertaken to connect the Mediterranean Sea and the German Ocean by means ofthe Rhone, the Saône and the Moselle, but the project was never completed. Emilius Scaevius, more successful, united the waters of the Po, near Placentia, for the purpose of draining the marshes round about. Other rivers in Italy were straightened, deepened, widened, or otherwise improved, while Rome was still “the mistress of the world.” [Illustration: CANAL ON LAKE FUCINO.] [Illustration: SECTION THROUGH SIDE.] Some twelve centuries later the Italians were the canal makers of Europe. Alberto Pittentino, in 1188, converted the Mincio, from Mantua to the Po, into a canal, thus restoring it to the course from which the Romans had diverted it in the time of Quintus Curtius Hostilius. The use of locks on canals may be said to date from this time. It is related that in the canalisation of the Mincio, Pittentino so regulated the rise and fall of the river that boats could ascend to Mantua and descend to Po, the depth being so equally maintained that the river was navigable for about twelve miles. This must have involved the employment of locks, however rude.[96] The Lake Maggiore is the source of the Tesino, which in its course is divided into several streams, which, however, are reunited before it enters the Po, near Pavia. For the whole distance it is navigable, although at Pan Perduto, where the fall is considerable, it is sometimes hazardous. Immediately below this spot commences the canal to Milan, which at Abbiate divides into two channels. The entire length of the excavation is about 32 Italian miles, and its breadth 70 Milanese cubits. The Canal della Martesana, by some supposed to have been executed by Leonardi da Vinci, was made in the year 1460, under the Duke Francis Sforza. Leonardi da Vinci joined the two canals some time during the reign of Francis I. The Canal della Martesana, which is drawn from the Adda, is 24 miles in length, and in width about 18 cubits; but when constructed at first, the water it contained was barely sufficient for navigation for more than two days in the week, and this only when all the openings for the purposes of irrigation were closed. One of the branches of this canal was carried for several miles by a stone dyke, and afterwards passed through a deep cutting. The other branch had its course through the rock, after which it was supported on one side by a lofty embankment, where it crossed the Molgara river by an aqueduct of three stone arches. Early in the thirteenth century, Bassanallo had a canal 11 miles long, which was navigated by the vessels that brought building stones to Venice. One of the several canals in the lagunes, on which the latter city is built, is 36 miles long. Between Padua and Venice, again, there is a canal some twenty miles in length, which has a fall of 50 feet, to overcome which four locks are provided. Milan, like Venice, is the centre of a network of canals. Here unite the great canal of Tesino and the branch from Pavia; the Muzza Canal, which commences at Cassano and ends at Castiglione, after traversing a distance of 40 miles; the canal of Abiato, made in the thirteenth century, which has a top breadth of 130 feet, and a bottom breadth of 46 feet; and the canal which connects Buffolaro, Biagrasso, and Arsago with Milan. Nor is Piedmont less rich in monuments and resources of the same description, having more than half a dozen canals which communicate with the Po at different points. Most of these canals are, however, of limited extent, the longest, called the Naviglio d’Inea, being 38 miles in length. The canals, large and small, in the Papal States, are so numerous that it would be wearisome to enumerate them. None are of great length, and most of them have been constructed rather with a view to drainage or irrigation than to navigation. Pagnani has left us an account of the levels and other operations of art, undertaken by former engineers, to ascertain whether some navigable canals might not be projected in Lombardy; and, above all, to determine the practicability of joining the Lake of Como with the neighbouring lakes. In the first place they found that the surface of the lake of Como was 48 braces lower than the surface of the lake of Cevate, 62 braces lower than that of the lake of Pusiano, and about 100 braces below that of the lake of Lugano; further, that the lakes of Como and Lugano are, at the point of their nearest approximation, in the valley of Porlezza, about six miles distant from each other; and that they are separated by a very high ridge, which would render any attempt at a navigable canal very arduous, even independently of the very great difference in the levels. The general map of Lombardy will, on a slight inspection, show these several places. The same engineers found that the scheme of running a canal from the lake of Lugano by the valley of the Olona to Milan was impracticable. It might, however, be possible to render the Olona navigable below Tredate, provided the waters were retained in the last trunk by means of some well-situated locks, and the upper mills were so placed as not to interrupt the bed of the river. In the project to render navigable the Tresa, which is the outlet by which the lake of Lugano discharges itself into the Lago Maggiore, these engineers found difficulties from the deficiency in the body of the water, and from the too great slope of the Tresa; to which it may be added that several torrents which enter it carry into it stones and gravel. It has been considered strange that these engineers never thought of another project, of which the execution would be easy, as well as convenient and useful—namely, to make navigable the Boza, which is the outlet of the little lake of Varese into the Lago Maggiore. The scheme of conducting a navigable canal from Milan to Pavia is of a much older date, having been designed for the purpose of joining the two canals of Milan with the Tesino, the Po, and the sea. Galeazzo Visconte, the father of Azzon, began its excavation. In 1564, the completion of the work was made the subject of considerable discussion. It was imagined that the expense could not be very great; and that by giving the sluices the common height, a great number would not be required. The enterprise was abandoned afterwards, because the canal of Bereguardo, although it did not reach the Tesino, was found sufficient to keep up the commerce between the two cities of Milan and Pavia. Pagnani, in the Treatise already referred to, mentions some other projects of a similar nature. _The Tiber._—In Italy another great undertaking has been agitated, namely, to render the Tiber navigable from Ponte Nuovo, below Perugia, to the entrance of the Nera, from which the navigation begins to be free and without interruption, to the sea. MM. Boltari and Manfredi reported on an inspection which they made of the Tiber in 1732. In this report they laid it down as a first principle, derived from experience, that to navigate any river with facility, particularly against the stream, it is requisite that the slope should not exceed 3 Roman palms per mile (a Roman palm is about 8½ English inches). Now, as the fall of the Tiber is 8 or 9 palms, they calculated that it would be very difficult to steer the boats down the river, and still more difficult to conduct them up against so rapid a stream, especially in some places where the fall was even greater, and where, consequently, the stream must, they held, remain impassable. They, moreover, pointed out the difficulties and the dangers which must be encountered in adopting the different expedients that had been proposed for reducing the excessive slope by weirs, for removing the detached stones by manual labour, for blowing up the obstructing rocks by mines, and for removing the bed, in certain places, by changing its course, or by contracting or enlarging its dimensions. The schemes proposed for rendering the bed of the Tiber navigable having been thus discredited, the same engineers inquired whether a canal for boats of a moderate size and suitable burden might not be formed parallel with the river; observing the nature of the soil through which the canal must pass, the different crossings that would be required from one side to the other, the number of dykes and sluices that would be wanted, and the other works that would be necessary to secure the navigation against all accidents, and particularly those from floods. This undertaking they regarded as very difficult of execution, and they advised that it should not be attempted. They next examined the plan of making the Tiber navigable to Rome, proposed by the engineer Chiesa, in a report printed in 1745, but nothing came of these proposals. Within the last two years, a new project has been brought forward with the view of rendering the Tiber navigable to the sea, and it is possible that this work will before long be attempted. _The Villoresi Canal._—The water for this canal is derived from the Ticino, at a place called “Rapida del Pamperduto,” by means of a weir thrown across the river. This weir is 290 metres (951·2 feet) long, and 24 metres (78·72 feet) broad, and of sufficient height to raise the water in the Ticino 3·75 metres (12·30 feet) above the ordinary low-water level. Below the right abutment the river-bank is protected by a wall for a distance of 50 metres (164 feet), whilst up stream, on the same side, an embankment, partly in masonry and partly in earthwork faced with stone pitching, has been constructed for a distance of 600 metres (1968 feet), in order to confine the river to its present bed. At right angles to the weir is a lock, with a drop of 6 metres (19·68 feet), the largest in Italy, which serves for the passage of boats from a channel below, 10 metres (32·8 feet) wide, and about one kilometre (0·62 mile) long, from the canal to the Ticino. The channel is supplied with water from the basin below the measuring weir by means of four sluices 0·80 metre by 1·20 metre (2·62 feet by 3·93 feet) placed in the wall which separates the basin from the canal. On the side of the basin, opposite the weir, are two buildings, the first containing the sluices, which admit 8 cubic metres (282·52 cubic feet) per second of water into a canal belonging to the Visconti family; and the second, which forms the entrance to the Villoresi Canal, serves to regulate and maintain the level of the water in the basin constantly at 0·90 metre (2·95 feet) above the crest of the weir. It consists of a three-storied building, in the lower part of which are six sluices, 2·30 metres (7·45 feet) wide, and 3 metres (9·84 feet) deep, with iron gates, worked by suitable mechanism from the floor above. The headworks, which are on the left bank, consist of a building 67 metres (219·76 feet) long, 6 metres (19·68 feet) wide, and 12·80 metres high, provided with thirty sluices, each of 1·50 metre (4·92 feet) clear width, and 3·25 metres (10·66 feet) high, the cills of which are placed at 2·75 metres (9·02 feet) below the level of the crest of the weir. These sluices are capable of admitting 190 cubic metres (6710·13 cubic feet) per second into the canal from the river, of which 70 cubic metres (2472·15 cubic feet) per second is the amount granted by the concession to the Villoresi Canal. The remaining 120 cubic metres (4237·98 cubic feet) per second have to be returned to the Ticino by a specially constructed measuring weir established at 600 metres below the headworks, in order to respect the existing rights of others further down the stream. The passage of boats from the Ticino to the canal is provided for by means of a channel with a lock 8 metres (26·24 feet) wide. _The Canals of Venice._—In speaking of the canals of Italy, it would be unpardonable to omit due reference to those which give to Venice, the “mistress of the Adriatic,” her peculiar and pre-eminent position. Founded in the year 452, soon after Attila invaded Italy, Venice is built upon a number of small islands, and is divided into two nearly equal parts by the “Grand Canal,” 1200 yards in length, and 100 feet in breadth. Many smaller canals branch off from the Grand Canal. These are crossed by some five hundred bridges, many of them of considerable architectural pretensions. The construction of the canals of Venice was a work that would be naturally unlike that of laying out a canal in the ordinary course. The whole city, built on a number of small islands, is more or less constructed on piles; there is an almost dead level throughout; and the waterways would, no doubt, in the majority of cases, be naturally formed, at least to a partial extent. There is, however, very little information extant as to the circumstances under which the work of adapting the canals to the requirements of the population was carried out. _Irrigation Canals._—It would hardly be proper to pass from the canal system of Italy without making some remarks on the excellent system of irrigation canals that has been provided in Lombardy and Piedmont. Navigation canals take priority over irrigation canals in Lombardy in point of origin, but not to a great extent. The Vettabbia Canal, which is supposed to have been used for navigation previous to the eleventh century, is claimed as the oldest existing canal in Lombardy. In the latter part of the twelfth century, the Cistercian monks of Chiaravalle obtained possession of this canal, and applied its waters to irrigation purposes. Not very long afterwards the same order of monks constructed the Ticinello, a canal derived from the Ticino at Tornavento, and it was used exclusively for irrigation until 1177, when it was enlarged and partly opened for navigation. In 1257, the same canal was so far enlarged as to connect Milan with Lake Maggiore, and the waterway is now known as the Naviglio Grande. One of the most important irrigation canals in Italy, which may be briefly described as illustrative of the system generally, is that of the Cavour Company, in Piedmont, which is derived from the left bank of the Po, near the town of Chivasso, and was constructed for the purpose of irrigating the provinces of the Vercellese, Novarese, and Lomellina. It was Francesco Rossi, a land surveyor of Vercelli, who, in 1844, first proposed to employ the waters of the Po for irrigation purposes. It was a good many years later, however, before the project was undertaken. The head works of the Canal Cavour are situated about 400 metres below the bridge over the river, on the road which connects Chivasso with the military road from Turin to Casale. The full discharge of this canal is 110 cubic metres per second, and its supply is obtained by means of a temporary dam of timber carried across the river. The sluice-house for regulating the supply of water to the canal is built across the canal, which is 40 metres in width, and consists of twenty-one openings separated by granite piers. Each opening is provided with three sluice-gates, which work in grooves cut in the granite piers, and can be easily raised or lowered by the sluice-keeper by means of a lever. The remainder of the building is constructed principally of dressed stone and bricks, and the contrast between the granite used for the quoins and the red brickwork has an excellent effect. Another sluice-house, placed at right angles to that of the main canal, communicates with that of the “Scaricatore,” or discharge channel, by means of which the surplus waters in times of floods may be discharged into the Po, and any deposit of gravel and sand on the floors in front of the entrance to the main canal can be effectually swept away by the velocity of the water discharged into the “Scaricatore,” which has a rapid fall, and enters the Po again, about 2 kilometres below the headworks. The quantity of material used in the construction of this important work was:— Excavation 695,000 cubic metres. Bricks 2,000,000. Dressed stone 3000 cubic metres. Stone for _revetment_ 3000 square metres. Lime 3500 tons. Oak piles 2200. Oak sheet piles 8100 square metres. Ironwork 39,780 kilos. The width of the canal, which is 40 metres wide at the commencement, is gradually lessened until it reaches the aqueduct over the Dora Baltea near the 10th kilometre of its course, when its width becomes 20 metres. The sides, when not protected by retaining walls, have an inclination of 45°. Crossing the valley of the Dora, which is about 2 kilometres in width, on a high embankment, and the actual bed of the same river, by means of an aqueduct consisting of nine arches of 16 metres span each, the canal takes a north-easterly direction nearly parallel to the railway from Turin to Milan, which it crosses near the station of San Germano. At the 40th kilometre the canal passes in syphon under the torrent Elvo. This syphon is built in brickwork, and consists of five elliptical openings, 5 metres in width and 2·30 metres in height. The next work of importance is the embankment and aqueduct over the torrent Cervo, and differs but little from that over the Dora. The most important work on the whole canal, with the exception of the headworks, is the syphon for passing underneath the torrent Sesia. It is similar in section to that previously described for the Elvo, but considerably longer, and is probably one of the largest works of this class in Italy. The next works in importance are the aqueducts for crossing the torrents Roasenda and Marchiazza, and syphons under the torrents Agogna and Terdoppio, near Novara. The width of the canal up to the 62nd kilometre is 20 metres, and as, at this point, a considerable quantity of water is introduced from it into the Roggia, Busca and Rizzo-Biraga, the canal is reduced to 12·50 metres in width to the 74th kilometre, when its section is again reduced, and after passing under the Terdoppio—at which point the new branch canal “Quintino Sella” is derived—its width is only 7·50 metres. The fall of the canal between the headworks at Chivasso and the Dora Baltea varies from 0·50 to 0·25 in 1000, and over the remainder—with the exception of aqueducts and syphons, when in some cases it is greater—the gradient is 0·25 per