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
1000. The total fall is 21·73. Besides the works just described, 480 of
less importance, consisting of bridges for roads, aqueducts, syphons
for the passage of existing water-courses and canals of irrigation,
watchhouses, &c., were constructed.
_The River Po._—The Po, which takes its rise at Mont Viso, crosses
the whole plain of Upper Piedmont, a plain formed of a deep alluvial
soil, very fertile, and well cultivated. Passing through territory of
Turin, it receives the drainage of the rich meadows, as also the sewage
of that town, and before reaching Chivasso it receives the rivers
Dora Riparia, Stura, Orco, and Malone. The waters of the Po in floods
are dense with rich alluvial matter, of the fertilising properties of
which evident proofs may be observed throughout the course of this
river. After great floods, as if by magic, bare shoals of gravel become
covered with a deep strata of alluvial soil, on which the seeds of
trees and shrubs carried down by the waters soon take root, and in
a very short time they are covered with a luxuriant vegetation. The
waters of the Po on this account are highly valued for irrigation,
as also from the fact of its temperature being higher than that of
its tributaries. The fertilising properties of this water are now
fully appreciated in Lomellina, where large tracts of land which were
formerly bare and arid wastes, are now converted into rich meadows and
rice fields, through the agency of the waters which have been brought
to bear upon them by the Canal Cavour, already alluded to.
Even in the Vercellese, where the want of water is not so much felt,
the waters of the Po, introduced into the existing canals, and mingling
with those of the Dora, tend to modify the extreme coldness of the
latter river, due to its origin in the glaciers of the Val d’Aosta and
the siliceous-magnesian sands that its waters contain in suspension.
It is, therefore, with just pride that Italians have named the Po the
“Nile of Italy.”
Although the Po is the only extensive river basin in Italy, there are
many other rivers in that country that are more or less navigable, some
of them inclined to the Tyrrhenian Sea, and some to the Ionian Sea, but
most of them, including the Po, to the Adriatic.
_Projected Canals._—Among the proposals recently put forward for
extending, by artificial means, the commerce and navigation of Italy,
one of the most important is designed to provide for the construction
of a ship canal to connect the Tyrrhenian Sea, and the Adriatic, near
Fano and Castro. The distance to be traversed by this canal would
be 175 miles, and the cost has been estimated at about 20 millions
sterling. It is claimed that the proposed canal would be of great
advantage to the navigation between the east and the west coasts of the
Peninsula.
In 1889 a company was formed in London for the purpose of establishing
a system of canal, lake, and river navigation in the north of Italy.
This company expects to carry a very large share of the traffic at
lower rates than those quoted by the railways.
FOOTNOTES:
[94] Ann., lib. xii. cap. 56.
[95] Æn., t.v. 563.
[96] “Before the introduction of locks, contrivances called conches
were in use to moderate the too great declivity of the rivers, and
which were opened to allow vessels to pass through. These openings
were 16 or 18 feet in width; a balance lever, loaded at the end, was
made to turn on a pivot, and with it three hanging posts, united by
an iron bar, which crossed them immediately above the sill; besides
these three perpendicular hanging posts were two others, let some
inches into the side walls. These five posts were all on the same
face, and the spaces between them were all equal. When the balance
beam turned upon its pivot, the three middle posts alone opened,
and allowed the boats to pass, after which the balance beam was
turned back to its former position. At a little distance was placed
another balance beam, having attached to it a wide plank, to allow
the lock keeper to pass over, as well as to place in the grooves
of the hanging posts the small planks which served to exclude the
water, by closing up the intervals; these were on the side opposed
to the current, and in number sufficient to keep the water at the
required level. Such gates, or contrivances for damming up the waters
of a river, were in use at a very early time in Italy, and two such
were constructed at Governolo, in the twelfth century, to pen up the
waters of the Mincio on the side of Mantua.”—Cresy’s ‘Cyclopædia of
Engineering.’