the great reservoirs of the Marcia at the lower level, the Anio Novus
is carried on an arcade across a valley and a small stream, at a place
called after the arcade Arcinelli. The great Villa of Hadrian is nearly
under this at the foot of the hill, perhaps a mile lower down. This
was supplied with water by branches from the aqueducts, but without
interfering with the main streams, which went on at the high level still
at least five hundred feet above the level of Rome. From this high
level the aqueducts led gradually down in a serpentine course, crossing
several narrow valleys or gullies through the hills, along which some
mountain-stream flows far below. At two important points, the aqueducts
have to be carried across such valleys or gullies on fine arcades or
bridges. The one nearest to Tivoli is called the bridge of S. Antony,
from a small chapel made in the Middle Ages, probably in the fourteenth
century, out of a portion of the _specus_ of the Marcia, in one of
the chambers of a _castellum aquæ_ belonging to it, the rest of which
has been destroyed. The _specus_ of the Anio Vetus under it has also
been destroyed, but the arcade is preserved for the use of horses and
foot-passengers. This bridge is about eight miles from Tivoli. There is
no carriage-road to it, but a tolerable path for horses or donkeys; it is
one of the finest and most picturesque objects on the whole line of the
Aqueducts, and is about 100 ft. above the water in the stream below which
is called the _fosse_ of S. Antony. This valley or gorge in the mountain,
with the bridge across it, is not easily seen from any distance; but
the site may be indicated by a medieval castle with a tall square brick
tower, which is a conspicuous object for miles. This is distinctly seen
from the bridge, and as it stands at the mouth of the valley, that object
must be seen from thence on looking up the valley. This bridge is a
really grand work; it is 373 ft. long, 16 ft. wide, and about 104 English
feet high. The dome of S. Peter’s at Rome is visible at a long distance
from the hill above the medieval castle.
Following the direction of the aqueducts towards Rome for about a mile,
along a very rough cross-country path, we arrive at a good carriage-road
from Rome to Poli, and about a mile beyond that is another magnificent
structure, as fine and more perfect than the last, called Ponte Lupo,
one of the greatest works of all the Roman aqueducts. There are not
so many open arches as at the bridge of S. Antony, but a greater
extent of substructure and wall at each end, and the height above the
mountain-stream is even greater. Several of the arches seem to have been
filled up for greater strength, at an early period; it is all work of
the first century. Here the two _specus_ of the Claudian and the Anio
Novus are perfect, one upon the other, and serve as a lofty parapet to
the road for horses, which passes across the valley along the side of
them, the _specus_ occupying about one-third of the width of the bridge.
The two _specus_ seem to have been first brought together at this point,
and afterwards continue one upon the other for the rest of their course
into Rome, interrupted only by the _piscinæ_ and _castella aquarum_ at
intervals.
There are ruins of another arcade across the valley at a lower level by
the side of this grand bridge, only a few yards from it, which can only
be that of the Marcia. The Anio Vetus appears to be carried across under
the Claudia and Anio Novus at a much lower level, and it is probably for
this reason that the arches are closed instead of being left open. They
pass upon four other bridges over the streams of S. Gregory and of the
Inferno, before they arrive at the _piscinæ_. They all four meet at this
point, and then diverge again for miles. This splendid work is about
ten miles from Tivoli, half-a-mile from the carriage-road, five or six
miles from the Villa of Hadrian, and out of the line of the direct road
to Rome, but very near the road from Rome to Poli. After passing these
great works, the aqueducts are continued at their respective levels in
the direction of La Colonna and of the _piscinæ_, and are carried in
tunnels through the hill, but these tunnels do not appear to be of any
great length; they merely pass through part of one side of the hill. They
bring us to the _piscinæ_, which are about six miles from Rome, where the
arcades begin, and from this point the Marrana follows the same direction
in the bed of the Almo, winding about but never very distant from the
arcades, and always receiving the surplus water. This stream is here
divided into two branches, one of which goes through Rome and into the
Tiber at the Pulchrum Littus; the other passes through the valley of the
Caffarella, and falls into the Tiber near the church of S. Paul beyond
the walls, as is explained under the head of the Aqua Crabra and the
Marrana.
The _specus_ of the Anio Novus is always faced with brick or with _Opus
Reticulatum_; it is carried _upon_ the Claudian arcade, and the one
_specus_ always rests upon the other: what applies to one applies to both
after the first junction. The aqueduct of Claudius has a stone _specus_
carried on a stone arcade for the last five miles into the city. It
was begun by Caligula, and carried on by his successor; this portion
was completed in fourteen years, a very short period for so enormous an
undertaking. The Anio Novus was the most abundant of all the aqueducts,
as stated by Frontinus[139].
The arches of aqueducts, stretching for miles across the open country
and entering Rome at the eastern angle, are the first objects to attract
the attention of strangers on approaching the city. These are the arches
of the Claudian aqueduct, built of large square stones, with the angles
chamfered off, and carrying the streams of the Aqua Claudia and of the
Anio Novus.
Of the _Piscinæ_ mentioned by Frontinus, the ruins of one remain at the
place now called Porta Furba, where the aqueducts just mentioned meet
again about two miles from the city. The lofty Claudian arcade passes
over the Marcian arcade at this point, at one of the numerous angles,
as it had previously done at the Torre Fiscale. From the Porta Furba to
Rome, the Aqua Felice is carried against the side of the Claudian, or on
the piers of the Marcian, as most convenient, frequently crossing from
one to the other on arches over the road. The _specus_ of the Felice
is built in the roughest manner of old materials taken from the other
two arcades. The Anio Vetus also passes underground at the Porta Furba.
Immediately after the entrance of the Claudian _specus_ into Rome at the
extreme east end, in the gardens of the Sessorian Palace (now S. Croce),
there are remains of at least four reservoirs or _castella aquarum_
before it reaches the Porta Maggiore[140].
Nero was the immediate successor of Claudius, A.D. 54-69, and carried on
the conduit into the city, on what are still called the arches of Nero,
which are faced entirely with brick, and some of the most beautiful
brickwork in the world. So gigantic a work as these aqueducts could not
have been completed in the lifetime of a single emperor, however large
the number of slaves he may have employed upon it.
THE NERONIAN ARCADE.
The arcade of Caligula and Claudius, which is entirely of stone,
terminates at the Porta Maggiore, the Esquilina of Frontinus. The work
of Nero includes the arches within the city from the wall close to the
Porta Maggiore to the great _castellum_ on the Cœlian, over the arch of
Dolabella. The _specus_ of the Anio Novus is easily distinguished from
the _specus_ of the Claudia, as the latter is of squared stone.
The arcade of the Claudia has been considerably repaired with brick, and
the arches filled up in several places with brickwork of the time of
Septimius Severus and Caracalla, A.D. 193-217. This may be distinctly
seen in that part of the arcade which is between two and three miles from
the city, near the Porta Furba. It was again repaired by Pope Hadrian I.
in 780, and several times by other Popes.
The remains of these two aqueducts, one above the other, are admirably
seen in their course along the top of the Porta Maggiore; and at this
spot their relative levels with regard to the Marcia, Tepula, and Julia,
are also clearly exhibited, the latter entering the wall close to the
gate, and almost at right angles to it. Thus, at one view, we are able
to see the _specus_ of five out of the nine aqueducts, mentioned by
Frontinus, actually remaining. A sixth, the Anio Vetus, also passes under
the Walls of Rome at the same point; the _specus_ is half underground,
and now concealed by the _restorations_ made in 1869.
An inscription upon the face of the _specus_ itself in the wall of the
city over the archway, records that Claudius the son of Drusus, caused
to be brought into the city the water of the Claudian conduit, from the
springs called Cæruleus and Curtius, from 45 miles distance; also the
water of the Anio Novus, from 62 miles, at his own expense[141]. These
dates here given correspond with the year 798 of Rome, or A.D. 45.
Great repairs were made by Vespasian and Titus to the Claudian aqueduct.
The distance from which the Anio Novus is brought, according to this
inscription[142], is 62 miles, which agrees with Frontinus[143].
The architect of the Claudian is believed to have been Claudius Annius
Bassus, mentioned by Tacitus as chief engineer at Carthage under Marcus
Silanus, the father-in-law of Caligula. The remains of the tomb of Bassus
may be seen near Vicovaro. The tomb of another architect and his family,
on the side of the _agger_ upon which the arcade of Nero stands, near the
Porta Maggiore, was excavated in 1865. From its situation immediately
under the _Neronian Arcade_ against the bank on which it stands, there
seems no doubt that this Tiberius Claudius Vitalis, whose name is
inserted on the front of the tomb, was the architect of the arcade; and
it does infinite credit to him, for it is one of the finest pieces of
brickwork in the world.
This arcade, commonly called the Arches of Nero, carried the _specus_ of
the Claudia[144] and Anio Novus combined. It first crosses the foss on a
double arcade, one upon the other, to give more height across this wide
and deep inner trench; it is then carried on a high bank, and therefore
on a single arcade only to the Lateran, and on another bank across the
foss between the Lateran and the City to the Cœlian, and along the north
side of S. Stefano Rotondo to the reservoir and _piscina_ over the arch
of Dolabella. This arch was the principal entrance to that part of the
Cœlian in which the _Claudium_, or courts and temple of Claudius, were
situated. There are magnificent ruins of a large _castellum aquæ_ over
this arch, faced with the beautiful brickwork of Nero; in part of this
the small church of S. Thomas in Formis has been made.
Another large subterranean reservoir remains perfect on the west side
of this lofty brick _castellum_ of Nero. This consists of three large
vaulted chambers under the garden between the church of the twelfth
century and the small monastery of the Redemptorists, now (1872) all
belonging to the Villa Mattei, or Celimontana. There is, through the
crown of each of the vaults, a circular opening, or well, closed by a
stone, which can be moved at pleasure for letting down buckets into the
water; it is still used for the purpose of irrigation. From the low
level of this reservoir, it must have belonged to the Aqua Appia. By the
side of the garden over this, and above ground, in a line with the Arch
of Dolabella, is a wall of the first century, faced with reticulated
masonry, probably part of the _castellum_ of that period, as new
reservoirs have been built there for each successive aqueduct that came
to this point. The highest, being that of Nero, was 50 feet above the
level of the ground.
Thence the water was distributed in different directions, one branch to
the Claudium[145], and thence again to the _stagnum_ or pool originally
of Nero, but afterwards retained under the Colosseum; a second to the
Palatine, passing down the western side of the Clivus Scauri opposite
to the church of SS. John and Paul. Then, after making one of the usual
angles, it was carried across the valley on the arches attributed to
Nero, but in this part really after his time, the lower portions of some
of which remain. The third branch was to the Aventine. The plan for this
was not carried out until the time of Trajan, when a lofty arcade was
made across the valley from the Cœlian to the Aventine, passing over the
Porta Capena above the Aqua Appia, which had previously been made in the
same line, and with new reservoirs for it, generally by the side of the
old subterranean ones. One great reservoir under the Cœlian occupies a
considerable part of the space between the cliff and the present road,
and is now turned into a gardener’s house. The excavations made there
in 1868 have been described in the account of the Appia; the piers of
the tall brick arcade of Trajan remain on both sides of the road leading
direct to the north end of the ruins of the Piscina Publica, on the other
side of the Marrana, under S. Balbina; the upper part of this great
building is of the time of Trajan. On the side of the Cœlian are remains
of another large _castellum_, of two stories, of the same period. There
are also remains of this aqueduct on the brow of the Aventine Hill, near
the church of S. Prisca, in front of the monastery, now in a vineyard
opposite to the Palatine, and overlooking the Circus Maximus.
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].
The springs called Cæruleus and Curtius, to which (when united in this
aqueduct) the name of Claudia[150] was given, as Frontinus tells us, are
situated in a valley on the south side of the river Anio, thirty-eight
miles from Rome, and eight miles below Subiaco (which is forty-six miles
from Rome), and not more than half a mile from the source of the Marcia.
Several streams issue from the rock under the present carriage-road, a
_diverticulum_ or branch of the ancient Via Valeria, and form a beautiful
small lake of very clear water having a distinctly bluish tint. Another
of these springs, the Albudinus, is still considered as equally good with
the Marcia, or nearly so. The Anio here flows at the opposite end of this
small valley, and both the lakes are now emptied into it. This valley
is in the territory of Arsoli, so called from a neighbouring village on
a height overlooking it, and the lake of S. Lucia. The spring called
Curtius is another of these streams.
This valley is admirably calculated for the sources of aqueducts; the
ground is full of springs of beautiful water, and the watery meadows have
only to be dammed up a little to form lakes or reservoirs. Probably the
water from these springs, which now runs into the river, was entirely
intercepted and carried into Rome in the aqueducts. The Anio is in
general such an abundant stream, that these additional springs would
scarcely be missed, although in time of severe drought the water did
sometimes run short[151].
The _piscinæ_, mentioned by Frontinus, were large subterranean reservoirs
and filtering-places, at seven miles from the old City or from the inner
gates, and six from the outer gates: the portion of Rome outside of the
walls of _the city_ was considered as the suburbs only, until the time of
Aurelian, when the City was made to extend to the outer wall, then newly
raised and fortified, but this was long after the aqueducts were made.
The present appearance of these two _piscinæ_ of the Claudia and the
Anio Novus is merely that of earthen mounds or tumuli. They are situated
about midway between the old Via Latina, which now in this part is made
into a carriage-road to Frascati, and the Via Appia Nova. The distance
from one road to the other is about a mile, and the _piscinæ_ are about
half-a-mile from each. The stream, which was originally a branch of
the Almo, and now conveys the water of the Marrana and the Aqua Crabra
united, runs near them, and received the surplus water from all the
aqueducts on this line. It is divided into two parts near the _piscinæ_,
one branch going through the valley called the Caffarella, and falling
into the Tiber near the church of S. Paul’s outside of the walls; the
other keeps near the arcades and reservoirs, and coming through Rome,
passes on the south side of the Cœlian. This branch had come from the
_piscinæ_ nearly parallel to the aqueducts; it winds about a good deal,
but is never distant from the line of the latter, now on one side and
then on the other. A further account of this will be found under the head
of the Marrana, in the second part of this chapter.
APPENDIX TO CHAPTER IV. PART I.
THE NINE AQUEDUCTS IN THE TIME OF FRONTINUS.
Having sketched the general history of each one of these aqueducts,
and the circumstances under which they were erected, it remains to
refer briefly to some of those details which Frontinus has handed down
to us, of the mode of management of the water. These details apply
equally to the whole series. First of all, the position which he and his
predecessors in office held was a very important and honourable one.
He had the entire responsibility of the water supply, and the absolute
control of seven hundred men employed to attend to their proper working,
to clean the _piscinæ_, and to repair the channels and pipes when needed.
Of these, 240 were appointed by the City, and the remaining 460 by the
Emperor. The channels in which the main stream of water was carried, and
the reservoirs (_castella_), and the _piscinæ_, were always lined with a
particular kind of cement, called _Opus Signinum_.
It has also been observed that the base of the channel is constantly
broken up by inequalities, or dips, if they may be termed so, as
if purposely introduced to agitate the water in its course, and,
consequently, to aërate it. No doubt also the inequalities, provided
they were rugged, would tend to check the passage of any earthen matter
held in solution by the water. Of most importance, however, and shewing
still more remarkably the engineering qualities of the builders of the
Aqueducts, were the ventilating-shafts which were introduced at proper
intervals. Such shafts were often used as wells also, to let buckets
down for water, and steps were cut on the sides for the _aquarii_ to
descend and remove obstructions. At about every half-mile the _specus_
forms an angle to break the force of the water, and at such points there
is usually a reservoir also. Advantage was taken of these angles for
the later aqueducts to be carried over the older ones, as at the Torre
Fiscale and the Porta Maggiore. These precautions, combined with the
system of _Piscinæ_, rendered the water constantly fresh, pure, and
wholesome.
From some considerable remains of the _Piscinæ_, the system can be
clearly made out. The building consisted of four chambers, two beneath
and two above. Supposing, for the sake of illustration, in the annexed
diagram, the letters [Illustration: A B C D] represent the four chambers.
The channel of the aqueduct, coming at a tolerably high level, enters the
chamber A. Thence the water passed (possibly over a large waste-pipe)
into the chamber beneath, B. Between B. and C. there were small holes
communicating through the wall (possibly provided with fine grating).
Through the roof of C. there was a hole, and the water passed upwards,
of course finding the same level in D. at its exit, as in A. at its
entrance; on leaving the _piscina_ the water was carried off into another
_specus_. By the aid of sluice-gates the water could be transferred
direct from chamber A. to chamber D. Access was obtained by an opening
to the chambers beneath, and the mud was from time to time cleaned out.
Curious details of the sluices, &c., have been found; but it is not easy
to determine their age, as the aqueducts have undergone so many repeated
alterations.
As a typical example of the size of the _specus_, or channel of the
Aqueducts, the Marcian may be taken, which measures in the opening five
Roman feet in height, two and a-half in breadth, and the thickness of the
wall on each of the two sides one foot. The roof of the Marcian being
surmounted by the Tepulan and Julian, no great solidity was needed; but
so far as can be ascertained, the roofs were generally of considerable
thickness, to prevent, as much as possible, the heat of the sun spoiling
the coolness of the water. The channels and general structure of the Anio
Novus and Claudian were larger in every respect, those of the Tepulan and
Julian somewhat smaller, as shewn by the accompanying diagrams.
It will be seen that the period of the construction of the nine aqueducts
which have been described, embraces some four centuries, as Frontinus was
employed in surveying them towards the close of the first century after
Christ, and the first aqueduct was commenced more than three centuries
before the Christian era. If we omit the Alsietina, which was on the
other side of the river, and which ought scarcely therefore to be taken
into account, the order of level follows almost exactly the order of
construction, the only exception being that of the Virgo. This increase
of height of level as each new aqueduct was added, is pointed out by
Frontinus in his eighteenth chapter.
It will be perhaps convenient to have the several aqueducts already
described represented in a tabular form, shewing the dates when they were
made, and the order as to level, together with the distances which they
traversed.
The aqueducts, especially those which were mostly underground, it will be
observed, made long detours, as compared with the direct line of road;
as, for instance, in the first on the list, the distance by road was but
eight Roman miles, but that by the channel of the aqueduct was eleven
miles. The total length of all the channels of the aqueducts, constructed
in less than four centuries, was upwards of 285.610 Roman miles, of which
242.697 miles were cut beneath the surface, and 42.918 miles carried on
substructure, arched or not, as the case required, above the surface of
the ground.