AQUAEDUCTUS
AQUAEDUCTUS (
ὑδραγωγία,
ὑπόνομος)--literally, a water-conduit--would, of
course, properly describe any channel for the passage of water; but the word
is used especially for the magnificent structures by means of which Rome and
other cities of the Roman empire were supplied with water, and which may be
described in general terms as channels, constructed as nearly as possible
with a regular declivity from the source whence the water was derived to the
place where it was delivered, carried through hills by means of tunnels, and
over valleys upon a substruction of solid masonry or arches.
1. Greek.
Among the Greeks in many cases. springs (
κρῆναι,
κρουνοί) were
sufficiently abundant to supply a considerable part of the great cities
with water; and great attention was paid to the preservation and
adornment of them: they were converted into public fountains by the
formation of a head for their waters, and the erection of an ornamental
superstructure; and were dedicated to some god or hero. Pausanias (
10.4.1) considers no place to deserve the
name of
city which has not such a fountain. We
are indebted to the same author and other Greek writers for accounts of
some of the most celebrated fountains: such as that of Theagenes, at
[p. 1.147]Megara (
Paus.
1.40.1); those of Peirene and Lerna at Corinth, where there were
many other fountains, as well as a Roman aqueduct erected by Hadrian
(2.3, § § 2, 3, 5; 4.5); that in the grove of
Aesculapius at Epidaurus (2.17.5); and several others (4.31, 32, 34;
7.5, 21; 8.13), of which we need only mention the
Enneakrounos at Athens, which was constructed by
Peisistratus and his sons, and of which Thucydides records the
interesting fact, marking the transition from the natural springs to the
artificial fountain, and showing the importance attached even to the
former, that “it was called Callirhoë formerly,
when the springs were visible”
(
φανερῶν τῶν πηγῶν οὐσῶν,
Thuc. 2.15;
Paus.
1.14.1): to this enumeration might be added the springs of
salt water in certain temples; as in those of Erechtheus at Athens, and
of Poseidon Hippius at Mantineia. (
Paus.
1.26.5;
8.10.4.)
In these cases we have no reason to suppose that there was anything more
than a fountain over or close to the springs, forming a head for the
water derived, either immediately, or by very short channels, from them.
But we are not without examples of constructions more nearly approaching
the Roman aqueducts in kind, though not in degree. That the Greeks, at a
very early period, had some powers of hydraulic engineering, is shown by
the drainage tunnels of the lake Copaïs, and the similar works
of Phaeax at Agrigentum [
EMISSARIUM]; and we have an instance of a channel for water
being carried through a mountain, to supply the city of Samos. The
height of the mountain was 150 orguiae (900 Greek feet); the length of
the tunnel was 7 stadia (7-8ths of a Roman mile, or about 1420 yards);
its section was a square of 8 Greek feet. The actual channel for the
water was cut below this, and was, if the text is right, 30 Greek feet
deep, and 3 wide; the water passed through pipes (
διὰ σωλήνων) from a copious spring, and was thus
brought to the city. (
Hdt. 3.60.) There are
still remains of this tunnel. Müller conjectures that the work
was one of those executed by Polycrates (
Archäol. d.
Kunst, § 81). Indeed many of the Greek waterworks
appear to date from the age of the Tyrants.
But from early times, the Greeks, where the needs of a city called for
it, constructed underground conduits following the undulations of the
surface or carried through the hills by tunnels, and closely resembling
the earlier Oriental aqueducts, of which they were probably imitations.
Thus the conduit which supplied the acropolis of Thebes was attributed
to Cadmus (Dicaearch. p. 143, Fuhr), and the canalisation of the
mountain torrents round Argos to Danaus (Strabo, viii. pp. 370, 388).
The Greek aqueducts were usually rectangular channels cut in the rock or
constructed of solid masonry, but in the Troad we have an instance of
one composed of earthenware pipes (Hahn,
Ausgrab. auf der Homer.
Pergamus).
At Athens the rocky part of the city was dependent on cisterns. Two
conduits entered the city on the east from the upper course of the
Ilissus, which lower down was canalised, and part of its water went to
supplement the
Enneakrounos, below which an underground
conduit ran from the river, repeatedly crossing under its bed, and
accessible to use by shafts, and finally carried to the Peiraeus. Below
the
Enneakrounos a stream from Hymettus was carried over
the Ilissus into the city. Later, two large conduits were constructed
from Lycabettus on the east and west of that mountain. A system of
canals from the Cephissus served to irrigate the olive-woods. (E.
Curtius,
VII. Karten von Athen.) Finally, Hadrian, at the
end of his reign, built an aqueduct of the Roman type, drawing its water
from the Cephissus. Among the finest and best preserved of Greek
aqueducts are those of Syracuse, which Thucydides (
6.100) tells us were laid under ground to bring
drinking-water into the city. They are still in use-one from the Anapus,
on the north, twelve miles long, which finally crosses under the Small
Harbour and feeds the fountain of Arethusa, and one from the springs of
Mount Crimiti on the south. (Schubring,
Philologus, 1865, pp. 577-638.)
Solon, according to Plutarch (
Plut. Sol.
23), ordained that water might be fetched from the public
fountains or wells to a distance of four stadia; beyond this, persons
must dig their own wells; but if any one dug to a depth of ten
orguiae without finding water, he was permitted
to take from his neighbour's well a pitcher of six
choës twice a day. Plato (
Leg. viii.
p. 844, A, B) mentions this law, which obviously refers to country life,
in vaguer terms, and also the conditions under which the waters of
streams might be diverted for irrigation. The public conduits were
superintended by
ἐπιστάται τῶν
ὑδάτων. Their office was apparently of some importance, as
it was held by Themistocles, who inflicted fines on fraudulent consumers
(Plut.
Themist. 31). The
κρηνόφυλακες and
κρήναρχοι were probably subordinate officers (Phot. and
Hesych.
s. vv.; Schömann,
Antiq. i. p. 416, E. T.). On Greek aqueducts see E.
Curtius,
Ueber
städtische Wasserbauten der Hellenen, in
Archäol. Zeitung, 1847.
2. Roman.
The Romans were in a very different position, with respect to the supply
of water, from most of the Greek cities. They at first had recourse to
the Tiber and to wells sunk in the city; but the water obtained from
those sources was very unwholesome, and must soon have proved
insufficient. Consequently, to supply the demands of the public baths
and the fullers, and later of the growing population, and later still of
the
naumachiae, they had recourse to public
works in order to bring pure water from a considerable distance--from
the hills, in fact, which surround the Campagna. The date of the first
aqueduct. is assigned by Frontinus to the year A.U.C. 441, or B.C. 312 (
de Aquaed. Urb. Rom.
4); and the number of aqueducts was gradually increased, partly at the
public expense and partly by the munificence of individuals, till, in
the time of Procopius, they amounted to fourteen (see p. 151 a); and,
even before they were all erected, they might well excite the admiration
which Pliny expresses with respect to the Claudian aqueduct (
H.
N. 36.123);--“But if any one will carefully calculate
the quantity of the public supply of water, for baths, reservoirs,
houses, trenches (
euripi), gardens, and
surburban villas, and, along the distance which it traverses, the
arches built, the mountains perforated, the valleys levelled, he
[p. 1.148]will confess that there never was anything
more wonderful in the whole world.”
The detailed description of the arrangements of the aqueduct will be
better understood, after an enumeration of the principal aqueducts by
which water was conveyed to Rome across the Campagna. Our knowledge of
the subject is derived almost entirely from the treatise
De
Aquaeductibus Urbis Romae, by S. Julius Frontinus, who was
curator aquarum (keeper of the
aqueducts) under Nerva and Trajan. It should be observed that the
Aquaeductus is often called simply
Aqua. There were nine aqueducts in the
time of Frontinus, of which four belong to the time of the republic,
while five were built in the reigns of Augustus and Claudius.
- 1. The Aqua Appia was begun by
the censor Appius Claudius Caecus (to whom also Rome was
indebted for her first great road), in B.C. 312. Its sources are
mentioned by Frontinus as near the Via
Praenestina, between the seventh and eighth
milestones. But this appears to be a mistake, as its real source
has been discovered in the reservoirs formed in the ancient
quarries, now called latomie della Rustica, about
50 feet below the level of the ground. Perhaps we ought to read
Via Collatina instead of
Praenestina (Middleton,
Ancient Rome, p. 466). Its termination was at
the salinae, by the Porta Trigemina. Its length was 11,190
passus, for 11,130 of which it
was carried under the earth, generally at a considerable depth;
and for the remaining 60 passus,
within the city, from the Porta
Capena to the Porta Trigenmina, it was
on arches. The distribution of its water began from the Clivus Publicius. (Frontin. 5; Liv. 9.29; Diod.
20.36; Aur. Vict. Vir. Illust. 34, who
confounds it with the Anio.) Its
subterranean specus has been
discovered in several places in Rome, especially at one point
where it passes through the old tufa quarries in the Aventine
near the church of S. Saba; its line near this point is now
traversed by the modern Via di Porta (Middleton; l.c.).
- 2. The Anio Vetus was commenced
forty years later, B.C. 272, by the censor M‘. Curius
Dentatus; but as the time of the censorship expired before the
work was completed, duumviri aquae
perducendae were appointed, and the aqueduct was
finished by M. Fulvius Flaccus, one of the duumvirs, the other
having died shortly after his appointment. The expense was
defrayed out of the spoils taken from Pyrrhus. The water was
derived from the river Anio, above Tibur, at a distance of ten
Roman miles from the city; but, on account of its windings, its
actual length was forty-three miles (ita
exigente libramento, Front.), of which length less
than a quarter of a mile only (namely, 221 passus) was above the ground. There are
considerable remains of this aqueduct below the Claudian
aqueduct, near the Porta Maggiore, and other
pieces of the specus and remains of large cisterns were
discovered while laying out the new streets Principe Amadeo,
Carlo Alberto, and Napoleone III. (Middleton, p. 467), and also
in the neighbourhood of Tivoli, which was supplied with its
water. It was built of blocks of peperino stone, and the
water-course was lined with a thick coating of cement. (Front.
6; Aur. Vict. Vir. Ill.. 43.)
- 3. The Aqua Marcia, one of the
most important of the whole, was built by the praetor Q. Marcius
Rex, by command of the senate, in B.C. 144. The want of a more
plentiful supply of water had been long felt, especially as that
furnished by the Anio Vetus was of
such bad quality as to be almost unfit for drinking; and, in
B.C. 179, the censors M. Aemilius Lepidus and M. Flaccus
Nobilior had proposed the erection of a new aqueduct; but the
scheme had been defeated, in consequence of Licinius Crassus
refusing to let it be carried through his lands. (Liv. 40.51, 7.) The two existing aqueducts had also fallen into
decay by neglect, and had been much injured by private persons
drawing off the water at different parts of their course. The
senate therefore commissioned the praetor Marcius to repair the
old aqueducts, and to build a third, which was named after him.
According to Fenestella (ap. Front.), 180 million sesterces were
voted for the purpose. Some writers have pretended that the
original construction of this aqueduct is to be ascribed to
Ancus Marcius, alleging a passage of Pliny (Plin. Nat. 31.41), and a medal
of the Marcian gens, family Philippus, which bears on the
obverse a head with the legend ANCVS,
and on the reverse a representation of an aqueduct, with the
letters AQVAMR (Aqua Marcia) between the arches, supporting an
equestrian statue with the legend PHILLIPPVS: but those who know anything of the history
of Roman family records will understand that this medal bears no
evidence to the point in question, and is simply a perpetuation
of two of the greatest distinctions of the Marcia gens, their alleged descent from Ancus,
and the aqueduct which bore their name; and Pliny's opinion is
simply one of his ludicrous blunders, arising probably from his
confounding Marcius Rex with the king Ancus Marcius. (Eckhel,
Doctr. Num. Vet. vol. v. p. 248.)
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Medal of the Marcia gens, recording the Aqua
Marcia.
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This aqueduct commenced three miles south of the Via Valeria, thirty-six miles from
Rome; its length was 61,710 1/2 passus, of which only 7463 were above ground;
namely, 528 on solid substructions and 6935 on arches. It
was high enough to supply water to the summit of the
Capitoline Mount. It was repaired by Agrippa in his
aedileship, B.C. 33 (see below, No. 5), and the volume of
its water was increased by Augustus, by means of the water
of a spring 800 passus from it:
the short aqueduct which conveyed this water was called the
Aqua Augusta, but is never
enumerated as a distinct aqueduct. Pliny states that the
water of the Aqua Marcia was
the coldest and most wholesome of all which was brought to
Rome; and Vitruvius and other writers refer to the
excellence of the water as being proverbial. Considelable
remains of it are still standing both above and below
Tivoli. (Frontin. 7, 12; Plin.
Nat. 31.41, who differs from Frontinus in some of
the details Strab. v. p.240;
Vitr. 8.3.1; D. C. 49.42; Plut. Cor. 1; Prop. 3.22, 24; [p. 1.149]Mart. 6.42, 18; Stat. Silv.
1.5, 25.) Its
specus can be seen, where
it passes over the arch built by Augustus below the specus of the Aqua Julia and Tepula (see No.
5).
- 4. The Aqua Tepula, which was built by the
censors Cn. Servilius Caepio and L. Cassius Longinus in B.C.
127, began at a spot in the Lucullan or Tusculan land, two miles
to the right of the tenth milestone on the Via Latina. Its water was slightly warm, whence
its name, tepula, a form of tepida. It was afterwards connected with
- 5. The Aqua Julia. Among the
splendid public works executed by Agrippa in his aedileship,
B.C. 33, was the formation of a new aqueduct, and the
restoration of all the old ones. From a source two miles to the
right of the twelfth milestone of the Via
Latina, he constructed his aqueduct (the Aqua Julia) first to the Aqua
Tepula, in which it was merged as far as the
reservoir (piscina) on the Via Latina, seven miles from Rome. From
this reservoir the water was carried along two distinct
channels, on the same substructions (which were probably the
original substructions of the Aqua Tepula, newly
restored), the lower channel being called the Aqua
Tepula, and the upper the Aqua
Julia; and this double aqueduct again was united
with the Aqua Marcia, over the
watercourse of which the other two were carried. The arch
bearing the three aqueducts, where it entered the city, is now
the Porta S. Lorenzo; and the rebuilding of this
part of the aqueduct by Augustus in B.C. 5 is recorded by an
inscription on the side of the specus of the Aqua Julia
(A in cut). Other restorations were made by Titus in A.D. 79,
recorded in an inscription on the frieze below (B in cut); by
Severus in 196; and by Caracalla in 212. The restoration by
Caracalla is recorded in an inscription, to make room for which
the moulded pediment has been cut away (C in cut).
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Arch built by Augustus where the three Aqueducts,
Julia, Tepula, and Marcia, pass over a road, now the Porta
S. Lorenzo. (From Middleton.)
A. Original inscription by Augustus.
B. Inscription recording restoration y Titus.
C. Inscription added by Caracalla.
D. Peperino arch of the Aqueduct.
E. F, G. Specus of the
Marcia, Tepula, and Julia.
H. Part of one of the towers of Aurelian's Wall.
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In Rome itself the three specus
were separated and carried in different directions. A
section of the three specus is
given below (see p. 153). The whole course of the Aqua Julia, from its source,
amounted to 15,426 passus, for
7000 of which its course was above ground, partly on massive
substructions and partly on arches. (Frontin. 8, 9, 19.)
- 6. The Aqua Virgo was also built
by Agrippa in his aedileship. In the same year, Agrippa,
according to Pliny (Plin. Nat.
36.121), erected for public use 700 basins or pools
(lacus), 500 fountains
(salientes), 130 castella, adorned with 300 statues and
400 marble columns. The main object of the Aqua Virgo was to supply the baths of Agrippa.
From a source in a marshy spot by the eighth milestone on the
Via Collatina, it was conducted
by a very circuitous route, chiefly under the ground, to the
M. Pincius, whence it was carried on arches
to a spot opposite the east side of the Pantheon. Its length was
14,105 passus, of which 12,865 were
underground; in its subterranean course it received the water of
numerous springs; and its water was as highly esteemed for
bathing as that of the Aqua Marcia
was for drinking. It is one of the aqueducts on the left bank of
the Tiber which are still in use, though on a [p. 1.150]much diminished scale. (See p. 151b.) The origin of
its name is variously explained. (Frontin. 10; D. C. 54.11; Plin. Nat. 31.42; Cassiod.
Var. 7.6; Ov. Tr.
3.12, 22; Mart. 5.20, 9, 6.42, 18, 11.47, 6.) “A
well-preserved piece of the ancient specus can be seen below the level of the
street, in the court of No. 12, Via del Nazzareno, behind
the Trevi fountain. The arches themselves, which are of
peperino, are buried, but the specus of massive travertine, decorated with an
entablature, is visible, and is perfectly preserved. On both
sides of the frieze is an inscription recording that this
part was rebuilt by Claudius in A.D. 52.” (Middleton,
p. 471.)
- 7. The Aqua Alsietina (sometimes called also
Aqua Augusta), on the other
side of the Tiber, was constructed by Augustus from the
Lacus Alsietinus (Lago di Martignano), which
lay 6500 passus to the right of the
fourteenth milestone on the Via
Claudia, to the part of the Regio
Transtiberina below the Janiculus.
Its length was 22,172 passus, of
which only 358 were on arches, its level being lower than that
of any other aqueduct; and its water was so bad that it could
only have been intended for the supply of Augustus's Naumachia, and for watering gardens. Its
reservoir was 1800 feet long by 1200 wide. (Frontin. 11.)
- 8, 9. The two most magnificent aqueducts were the Aqua Claudia and the Anio Novus (or Aqua Aniena Nova),
both commenced by Caligula in A.D. 38, and finished by Claudius
in A.D. 52. The water of the Aqua
Claudia was derived from two copious and excellent
springs, called Caerulus and
Curtius, near the thirty-eighth
milestone on the Via Sublacensis,
and it was afterwards increased by a third spring,
Albudinus, and by the waters of the Augusta. Its water was reckoned the best
after the Marcia. (Frontin. 13, 14:
cf. Suet. Cal. 21,
Claud. 20; Lamprid. Alex. 30.) Its
length was 46,406 passus (nearly 46
1/2 miles), of which 9567 were on arches and 609 on
substructions. Of a still greater length was the Anio Novus, which began at the
forty-second milestone, on the Via
Sublacensis, being taken from a dam constructed in
the bed of the river, and which received in addition, at the
thirty-eighth milestone, opposite the sources of the Aqua Claudia, a stream called the
Rivus Herculaneus. It was the
longest and the highest of all the aqueducts, its length being
nearly 59 miles (58,700 passus, of
which 9400 were above ground), and some of its arches 109 feet
high (Frontin. 15). In the neighbourhood of the city these two
aqueducts were united, forming two channels on the same arches,
the Claudia below and the Anio Novus above. An interesting
monument connected with these aqueducts is the gate now called
Porta Maggiore, which was originally a
magnificent double arch, by means of which the aqueduct was
carried over the Via Labicana and the Via Praenestina. The Porta
Labicana was blocked up by Honorius; but the arch
has been lately cleared of his barbarous constructions. Over the
double arch are three inscriptions, which record the names of
Claudius as the builder, and of Vespasian and Titus as the
restorers of the aqueduct. The annexed cut (after Hirt)
represents a restored section. By the side of this arch the
aqueduct passes along the wall of Aurelian for some distance,
and then it is continued upon the Arcus
Neroniani or Caelimontani, which
were added by Nero to the original structure, and which
terminated
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Section of the Porta Maggiore at Rome:
a. the Aqua Claudia; b. the Anio
Novus; c. openings to give vent to the
air.
|
at the temple of Claudius, which was also built by
Nero, on the Caelius, where the
water was probably conveyed to a castellum already built for the Aqua Julia, and for a branch of the Aqua Marcia, which had been at some
previous time continued to the Caelius. The Arch of Dolabella, erected B.C. 10, was
used as a foundation for a large reservoir constructed at that
point. The ruined arches of the Claudian aqueduct still extend
for many miles across the Campagna.
These nine aqueducts were all that existed in the time of Frontinus, who
thus speaks of them collectively, in terms which can hardly be thought
exaggerated: “Tot aquarum tam multis necessariis molibus pyramidas
videlicet otiosas compares, aut inertia sed fama celebrata opera
Graecorum.” It has been calculated that these nine aqueducts
furnished Rome with a supply of water equal to that carried down by a
river thirty feet broad by six deep, flowing at the rate of thirty
inches a second. The total water supply of Rome has been estimated at
332,306,624 gallons a day, or, taking the population at a million, 332
gallons a head. 40 gallons a head is now considered sufficient. But the
demands for public purposes and for irrigation were large. There was
also another aqueduct, not reckoned with the nine, because its waters
were no longer brought all the way to Rome. This was the
Aqua
Crabra, which had its
[p. 1.151]source near
that of the
Julia, and which was originally
carried right through the Circus Maximus; but the water was so bad that
Agrippa would not bring it into the
Julia,
but abandoned it to the people of the Tusculan land; hence it was called
Aqua Damnata. Cicero had to pay to the
city of Tusculum an acknowledgment for its use. At a later period, part
of its water was brought into the
Aqua
Julia, but it was again cut off from the Julia by Frontinus,
and restored to the people of Tusculum (
Cic.
Agr. 3.2,
9;
Balb. 20, 45;
Fam. 16.18, 3; Frontin. 9).
It is now made use of in its course through the Campagna for watering
cattle and sheep (Burn,
Rome, p. 359).
There are still two aqueducts of later construction to be added to the
list.
- 10. The Aqua Trajana was brought by Trajan from the
Lacus Sabatinus (now
Bracciano), to supply the
Janiculus and the Regio
Transtiberina. Its construction is recorded on coins
of gold, silver, and bronze, of the years 110 and 111 A.D. (Eckhel,
Doctr. Num. Vet. vi. pp. 425, 428). Trajan also
restored and improved the other aqueducts, especially the Anio Novus (Frontin. 92, 93). The castellum
of this aqueduct on the Janiculan hill is shown on the coins of
Trajan. The aqueduct was restored by Belisarius, after it had been
injured by the Gothic king Vitiges in A.D. 537.
- 11. The Aqua Alexandrina was
constructed by Alexander Severus, A.D. 226; its source was in the
lands of Tusculum, about fourteen miles from Rome, between Gabii and
the Lake Regillus. Its small height shows that it was intended for
the baths of Severus, which were in one of the valleys of Rome.
(Lamprid. Alex. Sev. 25; Fabretti,
Diss. 1.23.) Parker, from an inscription of Hadrian
found on its collecting reservoir, attributes Fabretti's Alexandrina to Trajan or Hadrian, holding
the real Alexandrina to have been a
branch from the Anio Novus.
There may have been some other aqueducts constructed at a later time,
since Procopius (
B. G. 1.19) mentions fourteen as still
preserved in Rome in his time; but there is difficulty in making up this
number. He seems to have included as separate aqueducts some which were
only branches of those already mentioned. Thus we read of the
Aqua Septimiana, built by Septimius Severus, which
was, perhaps, only a branch of the
Aqua
Julia, formed by the emperor to bring water to his baths
(Fabretti,
Diss. 3.285). The
Aqua Algentia
seems to have been a name invented from a corrupt reading of
Alsietina (Middleton, p. 475). Other authorities give
a still larger number of aqueducts. Thus the
Epilogus to the
Notitia mentions
the
Ciminia, the
Severiana,
and the
Antonia
(
Antoniniana), and makes the whole number nineteen.
Great pains were taken by successive emperors to preserve and repair the
aqueducts. From the Gothic wars downwards, they have for the most part
shared the fate of the other great Roman works of architecture, their
situation and purpose rendering them peculiarly exposed to injury in
war; but still their remains form the most striking features of the
Campagna, over which their lines of ruined arches, clothed with ivy and
the wild fig-tree, radiate in various directions. Three of them still
serve for their ancient use; and these three alone, according to
Tournon, supply the modern city with a quantity of water much greater
than that which is furnished to Paris by the Canal de l'Ourcq, for a
population six times as large. They are: (1.) The
Acqua
Vergine, the ancient
Aqua Virgo,
which was restored by Pope Pius IV. and further embellished by Benedict
XIV. and Clement XIII. The chief portion of its waters gush out through
the beautiful
Fontana di Trevi, but it also supplies the
fountains in the Piazza di Spagna and the Piazza Navona, together with
ten smaller ones, and the greater part of the lower city. (2.) The
Acqua Felice (A.D. 1587), named after the conventual
name of its restorer, Sixtus V. (Fra Felice), probably brings the waters
from the spring of the
Alexandrina, partly
on the piers of the
Claudia. It supplies
twenty-seven public fountains, and the eastern part of the city. (3.)
The
Acqua Paola, the ancient
Trajana and
Alsietina, now united and restored by Paul V. (1611),
supplies the
Trastevere and the Vatican, and feeds, among
others, the splendid fountains before St. Peter's. Besides these, the
Acqua Marcia-Pia (1870) brings to Rome in pipes the
old
Aqua Marcia, which has now regained its
ancient repute. Of the ruins of the other aqueducts the most extensive,
within Rome, are those of the
Arcus
Neroniani and of the
Aqua Crabra; the most
interesting are the
Porta Maggiore, with the two channels
of the
Aqua Claudia and
Anio Novus (see p. 150), and the remains of the triple
aqueduct of Agrippa, passing over a road, and resting upon an arch, now
the
Porta S. Lorenzo, already described (see p. 149).
The magnificence displayed by the Romans in their public works of this
class was by no means confined to the capital; for aqueducts more or
less stupendous were constructed by them in various and even very remote
parts of the empire,--at Athens, Corinth, Catana, Salona, Nicomedia,
Ephesus, Smyrna, Alexandria in the Troad, Syracuse, Metz, Clermont in
Auvergne, Nîmes (the Pont du Gard; see below), Lyon, Evora,
Merida, and Segovia. Those at Ephesus and Alexandria were built by
Hadrian and Herodes Atticus, and that at Athens was commenced by Hadrian
and finished by Antoninus Pius, who also built those at Corinth and
Nicomedia. That at Evora, which was built by Quintus Sertorius, is still
in good preservation ; and at its termination in the city has a very
elegant
castellum in two storeys, the lower
one of which has Ionic columns. Merida in Spain, the Augusta Emerita of
the Romans, who established a colony there in the time of Augustus, has
among its other antiquities the remains of two aqueducts, of one of
which thirty-seven piers are standing, with three tiers of arches; while
of the other there are only two which form part of the original
constructions, the rest being modern. But that of Segovia, for which
some Spanish writers have claimed an antiquity anterior to the sway of
the Romans in Spain, is one of the most perfect and magnificent works of
the kind anywhere remaining. It is entirely of stone, and of great
solidity, the piers being eight feet wide and eleven in depth; and,
where it traverses a part of the city, the height is upwards of a
hundred feet, and it has two tiers of arches, the lowermost of which are
exceedingly lofty. The
Pont du Gard, carrying an aqueduct
across the valley and
[p. 1.152]stream of the Gardon
into Nemausus (Nîmes), consists of two tiers of noble arches,
surmounted by a tier of small arches which bear the
specus, the whole height of the three tiers being about
155 feet.
It will be observed that when the pacification of the Campagna permitted
Rome to look afield for a supply of water, the first great work
constructed was entirely underground, except for a short distance inside
the walls. Moreover
|
Aqueduct near Nemausus, now called the Pont du Gard.
|
we may divide the aqueducts described by Frontinus into those
at a low level, intended to supply the low-lying districts and for the
most part carried underground, and those at a high level, designed to
reach the higher parts of the city; and in the latter alone were arcades
and substructions largely employed. Frontinus (18) says that five
reached the highest parts of the city, and he gives them in the
following order: 1.
Anio Novus, the highest
of all. 2.
Claudia. 3.
Julia. 4.
Tepula. 5.
Marcia. Then follow the lower, constructed to a great
extent underground. 6.
Anio Vetus. 7.
Virgo. 8.
Appia. 9.
Alsietina, the lowest of all,
supplying the district beyond the Tiber and the lowest spots. The
aquae from the upper waters of the Anio
(
Anio Vetus, Marcia, Anio Novus,
Claudia) made a considerable détour southwards to
follow the high ground by Pedum, Labicum, and Frascati, and then cross
the Campagna more directly for Rome, following more or less closely the
course of the
Via Latina.
Why did the Romans waste so much labour and money on works the purpose of
which might have been effected much more economically by the simple plan
of laying pipes along the ground, with which they were certainly well
acquainted? (
Vitr. 8.7.) Aqueducts, it is
true, are often constructed in modern times in a suitable country; as,
for instance, the New River for the supply of London, and the aqueduct
of the Croton River for New York: but surely a modern engineer, if asked
to convey water from the upper course of the Anio across the low-lying
parts of the Campagna to the tops of the Seven Hills, would, like the
engineer of the new
Acqua Marcia-Pia, propose to carry
out the undertaking by laying down pipes. This question was formerly
answered by saying that the Romans did not know that “water finds
its own level.” But this is contradicted by the express
statement of Latin authors (
Plin. Nat.
31.57, “subit altitudinem exortus sui ;”
Vitr. 8.6.5, and 7.6, where he describes
the application of the principle to an aqueduct), by the whole
arrangements for the distribution of the waters of the aqueducts to the
upper rooms of their houses, and from the very existence of their
numerous fountains. As a decisive ocular demonstration we give a section
of one of the many fountains still existing at Pompeii. Possibly,
however, they did not recognise that the law would hold over so extended
an area. Frontinus at any rate, an excellent authority on Roman
engineering, theoretical and. practical, does not contemplate its
applicability.
|
Section of a fountain at Pompeii.
Section of a fountain at Pompeii. a, a. The ascending pipe.
b, b. The basin, made of blocks of
travertine.
|
Indeed it is very doubtful whether Roman engineers would have been found
equal to the task of conveying by an underground channel a large stream
of water subject, like that from the upper Anio, to a high pressure.
Their conduits were always pierced by shafts at intervals of one or two
actus, designed to avoid the supposed
danger of the walls being burst by the compressed air inside. Now these
shafts, sunk in the low-lying parts of the Campagna, would of course
make it impossible to force the water to the tops of the hills; they
were confessedly designed to relieve the pressure: and engineers were
probably led to use them, and thus explain their use by the bursting of
unpierced conduits conveying water at high pressure. If they had
recourse to pipes, the joints would present great difficulties, and
probably for such large volumes of water iron pipes would alone be
sufficiently strong, and the casting of pipes of such dimensions would
have been beyond their power. Moreover, as Mr. Middleton observes (p.
453), “the calcareous deposit with which water from the
neighbourhood of Rome so rapidly encrusts pipes and water-channels
made it doubly convenient
[p. 1.153]to employ
channels which were always readily accessible, and could be cleared
out without any difficulty.”
A strip of land 15 feet wide, marked at intervals by
cippi or boundary-stones, was left on either side of the
aqueduct, upon which no encroachments were allowed under penalty of a
heavy fine. All trees were in particular forbidden to be planted, lest
their roots should injure the substructions or arches of the aqueduct
(Frontin. 127). The
cippi or
boundary-stones seem to have been first placed by Augustus, but were
discontinued by the later emperors, since of the 31
cippi still extant, 22 bear the name of Augustus, three
of Tiberius, two of Claudius, and the other five are restorations
(Lanciani,
I Comentarii di Frontino, p. 345).
We proceed to describe in detail the construction and arrangements of
Roman aqueducts. There are three matters to be considered: the source
from which the water was derived; the aqueduct itself, by which it was
conveyed; and the reservoir in which it was received, and from which it
was distributed for use.
(1.)
The Sources.--It is unnecessary to follow Vitruvius
into the minute rules which he lays down for the discovery of springs,
where they were not naturally visible, and for testing the quality of
the water: it is enough to refer to his statements as showing the
importance attached to these points. (
Vitr.
8.1.) It was also necessary that the springs should have such an
elevation, as that, after allowing for the fall necessary to give the
channel its proper inclination, the water should enter the final
reservoir at a sufficient height to permit of its distribution for
public and private use; for there were no engines used, as in modern
waterworks, to raise the water to a higher elevation than that to which
it rose of itself. When the source had been fixed upon, whether it was
an open spring (
fons), or one got at by
sinking a well (
puteus), a head was dug for
the water, and enclosed with a wall; and, if necessary, the supply was
increased by digging channels from neighbouring springs: the rules for
these operations also are minutely laid down by Vitruvius (
8.7, s. 6, § § 12-15). Such a
reservoir was called
piscina, sometimes
piscina limaria (Frontin. 15), in which
the water might deposit any sediment it contained.
(2.)
The Channel (
specus,
sometimes
canalis),
or Aqueduct
itself.1--In order to convey the water from its source to its
destination, a channel was constructed, having a slight and, as nearly
as possible, a uniform declivity. An elaborate description of the means
adopted to secure this object is quite needless for readers of the
present day, as they were almost precisely similar to those with which
we are familiar in our railways: hills were pierced through by tunnels,
and valleys crossed either by solid substructions or arches of masonry,
according to the height required; and of these arches there were often
two tiers, and sometimes even three. The material employed was generally
stone (usually travertine or peperino), but sometimes rubble faced with
brickwork (as in the
Arcus Neroniani, the
Anio Novus, the
Alexandrina) or with
opus
reticulatum (as in the
Anio
Novus). The channel itself (
specus,
canalis) was a trough of brick or stone, lined with very hard
cement (
opus signinum), made of lime, pozzolana,
and pounded pottery or brick. and covered with a coping, which was
almost always arched, and the bottom of the channel was also curved. The
water either ran directly through this trough, or it was carried through
pipes laid along the trough. When the channel was carried beneath the
surface, if the hill through which it passed was of rock, it was merely
cut in the rock; but if of earth or sand, it was constructed of blocks
of stone.
The construction of the
specus will be seen
from the annexed drawing, which represents a section of the triple
aqueduct of Agrippa. (See above, p. 149.)
|
Section of the specus of the
triple Aqueduct of Agrippa. (From Middleton.)
A, B, C. Specus of the Aquae
Julia, Tepula, and Marcia. The top and bottom of each is of travertine,
the sides of tufa or peperino: they are lined with opus signatum.
D. Peperino arch.
E. Specus of the Aqua Julia at another point, where it has been
restored in concrete and brick.
|
The object of covering the
specus was to
exclude the sun and rain, and other obstructions; but it was necessary
to provide a vent for the air, which otherwise, they thought, would have
been compressed to such a degree as to burst the walls or roof of the
specus. The vent-holes (
spiramina) were made at regular intervals in the
roof of the
specus, or, when another
channel passed over it, in the side. They are represented in the
sections, given above, of the
Aqua Claudia
and
Anio Novus (p. 150). To ventilate the
subterranean channel of an aqueduct, a shaft (
puteus) of masonry was carried to the surface of the ground
at intervals of an
actus, or 120 Roman feet
(or two
actus,
[p. 1.154]according to Pliny, who calls them
lumina), as shown in the following woodcut
(after Hirt),
|
Shaft for ventilation of an Aqueduct.
Shaft for ventilation of an Aqueduct. a, the water-course; b, steps giving access to it; c, the shaft; d, e, section of
the specus and shaft; f, transverse section of them.
|
which represents the plan, longitudinal section, and
transverse section of part of a
rivus
subterraneus, the ruins of which still exist at Palmyra.
The
rivus subterraneus possessed the
advantage over the
aquaeductus of being
less exposed to variations of temperature, and more secure from injury;
on the other hand, it was of course more difficult to get at when it
required repairs. A reference to the account of the Roman aqueducts
given above will show how large a portion of them were subterranean.
Instead of, or within, the
specus, pipes
(
fistulae, tubuli) were often used for
the passage of the water. They were of lead, or terra-cotta (
fictiles), and sometimes, for the sake of
economy, of leather. The rules which Vitruvius lays down apply
particularly to leaden pipes, although he gives the preference to the
earthen ones, chiefly on the ground that the water which passed through
them was more wholesome. The pipes were made in lengths of not less than
ten feet, and of various widths, which were denominated in the manner
explained under
FISTULA
They were cemented together at the joints, which in earthen pipes were
made to overlap; and when the water was first let in, ashes were mixed
with it, in order that they might settle in the joints and stop them
more completely. The use of pipes permitted variations to be made in the
construction of the aqueduct: namely, the water could be carried round
instead of through a hill, if the circuit was not too great; and in very
wide valleys the costly structure of arches could be dispensed with. In
this case, a low horizontal substruction was made across the bottom of
the valley, and the pipe was brought down the one slope, along this
substruction, and up the opposite slope, to a height of course somewhat
less than that of the opposite side. The horizontal part of the pipe
across the bottom of the valley (
venter)
had ventilating openings for the escape of the air. At the bendings,
instead of the pipe, an elbow was bored in a solid piece of stone, into
which the ends of the adjacent pieces of pipe were securely cemented.
(For further details, see Vitruvius.) In those places where the pipes
were laid on the surface, reservoirs were sometimes made, at intervals
of 200
actus (24,000 feet), in order that,
if a part of the pipe needed repair, the supply of water might not be
entirely cut off. The advantage in the use of pipes, according to
Vitruvius, was the facility of repairing them.
The slope (
fastigium) on which the aqueduct
was built, in order to give the water a proper fall (
libramentum), ought not, says Vitruvius (
8.6), to be less than half a foot in every 100
feet (1 in 200); but Pliny only allows a
siciicus (a quarter of an inch) in 100 feet. The great circuit
which most of the aqueducts of Rome made, was taken chiefly (as is the
case with the New River) to prevent the too rapid descent of the water.
There is, however, a considerable variation in their declivities: for
example, the
Aqua Marcia and the
Aqua Claudia, though of such different heights
at Rome, have their sources at the same elevation.
Besides the reservoir or
piscina at the
source of the aqueduct, there were similar reservoirs at convenient
points in its course, especially at the middle and end. The construction
of these reservoirs will be understood from the following woodcut, which
represents a restored section of one which still exists.
|
Piscina, or reservoir of an Aqueduct.
|
The water flowed from the aqueduct a into the first upper chamber, thence
down and up again through the openings
b, c, e,
into the second upper chamber, out of which it passed into the
continuation of the aqueduct
f, having deposited
its sediment in the two lower chambers, which could be cleaned out by
the door
d. The
piscina was not always vaulted: Hirt, from whose work the
above cut is taken, gives also an engraving of an open
piscina. These reservoirs were not always used:
for example, the
Aqua Virgo and the
Alsietina were without them. They were especially
necessary when the water was conveyed through pipes. They were also used
as reservoirs for the supply of the neighbouring country, chiefly for
the purposes of irrigation.
The details which we have now been noticing are minutely described by
Frontinus, and by Vitruvius (
8.7, s. 6), and
briefly by Pliny (
Plin. Nat. 31.57).
(3.)
The Termination of the Aqueduct, and the Arrangements for the
Distribution of its Water.--The water, when it reached the
walls of the city, was received in a vast reservoir called
castellum aquarum, which formed the
head of water. (
Vitr.
8.6;
Plin. Nat. 36.121;
Frontin. 35;
Dig. 43, tit. 20.) The more
ancient name in use, when the aqueducts were first constructed, was
dividiculum. (Festus, s. v.) From this principal
castellum the water flowed into other
castella, whence it was distributed for
public and private use. The term
castellum,
[p. 1.155]is sometimes also applied to the intermediate
reservoirs already mentioned.
The chief
castellum was, externally, a
highly decorated building: for example, that of Hadrian, at Athens, was
adorned with Ionic pillars, and that at Evora, in Portugal, had the form
of a circular temple. Internally, there was generally one vast chamber,
lined with hard cement (
opus signinum), with a
vaulted roof supported by massive pillars, into which the water flowed
from the aqueduct, and from which it was conducted through pipes of
fixed dimensions into three smaller reservoirs, which were, however, so
arranged, that the middle one was only supplied from the overflow of the
other two. Of these three reservoirs, the two outer supplied
respectively the public baths and the private houses, and the middle one
the public ponds and fountains (
lacus et
salientes); so that, in case of a deficient supply for useful
purposes, none would be wasted on the fountains: the arrangement also
enabled a proper account to be kept of the quantity supplied for private
use, for the protection of the revenue derived from this source. (
Vitr. 8.7, s. 6, § § 1, 2.)
The minor
castella, which “received
the water from this chief head, were distributed over the city, in
such a manner that the
Aqua Appia
supplied seven
regiones by means of
twenty
castella; the
Anio Vetus, ten
regiones
through thirty-five
castella; the
Marcia, ten
regiones through fifty-one
castella; the
Tepula, four
regiones through fourteen
castella; the
Julia,
seven
regiones through seventeen
castella; the
Virgo, three
regiones
through eighteen
castella; the
Claudia and the
Anio
Vetus, ninety-two
castella.” (Frontin. 79-86.) For an account of the
parts of the city supplied by the different aqueducts, see Becker,
Handb. d. Röm. Alterth. vol. i. pp. 707,
708.
The ruins of the magnificent
castellum of
the
Aqua Julia, built by Alexander Severus
on the Esquiline, may be seen in the Piazza Vittorio Emmanuele.
“It is shown with some minuteness on medallions of Alexander
Severus. (See Froehner,
Med. Rom. p.
169.) It was excavated, and careful drawings of it were made by some
Prix de Rome students in 1822. It was again and more completely
exposed in 1877, and no lead pipes were found leading from it, as
would have been the case if it had been an ordinary castellum for
the
erogatio. The so-called
Trophies of Marius, made in the reign of
Domitian, were set on the exterior of this building, whence they
were moved in the 16th century to the top of the Capitoline
stairs.” (Middleton, p. 458.) It is now much dilapidated, but was
tolerably entire about the middle of the 16th century, as may be seen by
the drawing published by Gamucci (
Antichità di
Roma, iii. p. 133) from which this restoration is made. The
ground-plan explains part of the internal construction, and shows the
arrangement adopted for disposing of the superfluous water of an
aqueduct. The general stream of water is first divided by the round
projecting buttress into two courses, which subdivide themselves into
five minor streams, and finally fall into a reservoir.
The
castella were divided into two classes,
the
publica and
privata.
The
castella publica were again subdivided
into six classes, which furnished water for the following uses:--(1) The
Praetorian camp (
castra); (2) the ponds and
fountains (
lacus et
|
Castellum of an Aqueduct, called the “Trophies of
Marius.”
|
salientes); (3) the circus, naumachiae, and
amphitheatres (
munera); (4) the baths, and
the service of certain important handicrafts, such as the fullers,
dyers, and tanners (
opera publica); (5)
irregular distributions made by the special order of the emperor
(
nomine Caesaris); (6) extraordinary
grants to private individuals by the favour of the prince (
beneficia Caesaris). The distribution under each
of these heads is described by Frontinus, who enumerates the various
laws relating to water supply,
Jus ducendae
tuendaeque Aquae (Frontin. 3, 78).
The
castella privata were, as the name
implies, for the supply of private houses. When a supply of water from
the aqueducts was first granted for private uses, each person obtained
his quantum by inserting a branch pipe, as we do, into the main; which
was probably the custom in the age of Vitruvius, as he makes no mention
of private reservoirs, for which at first there was no occasion, as
there was a constant supply of water. Indeed, in early times, all the
water brought to Rome by the aqueducts was applied to public purposes
exclusively, it being forbidden to the citizens to divert any portion of
it to their own use, except such as escaped by flaws in the ducts or
pipes, which was termed
aqua caduca
(Frontin. 94). But as even this permission opened a door for great
abuses from the fraudulent conduct of the
aquarii, who damaged the ducts for the purpose of selling the
aqua caduca; and as the subsequent
method of supply required the main-pipe to be punctured in too many
places (Frontin. 27), a remedy was sought by the institution of
castella privata, and the public were
thenceforward forbidden to collect the
aqua
caduca, unless permission was given by special favour
(
beneficium) of the emperor (Frontin.
111). The
castella privata were built at
the joint expense of the families supplied by them; but they were
considered as public property, and were under the control of the
curatores aquarum (Frontin. 106). The
right of water (
jus aquae impetratae) did
not follow the heir or purchaser
[p. 1.156]of the
property, but was renewed by grant upon every change in the possession
(Frontin. 107).
The leaden cisterns, which each person had in his own house to receive
the water laid on from the
castellum
privatum, were called
castella
domestica.
All the water which entered the
castellum
was measured, at its ingress and egress, by the size of the tube through
which it passed. The former was called
modulus
acceptorius, the latter
erogatorius. To distribute the water was termed
erogare; the distribution,
erogatio; the size of the tube,
fistularum or
modulorum
capacitas, or
lumen. The smaller
pipes which led from the main to the houses of private persons, were
called
punctae; those inserted by fraud into the
duct itself, or into the main after it had left the castellum,
fistulae illicitae.
The
erogatio was regulated by a tube called
calix, of the diameter required
(
lumen), and not less than 12
digiti long (9 inches), attached to the
extremity of each pipe, where it entered the castellum; it was probably
of lead in the time of Vitruvius, such only being mentioned by him; but
was made of bronze (
aeneus) when Frontinus
wrote, in order to check the roguery of the
aquarii, who were able to increase or diminish the flow of
water from the reservoir by compressing or extending the lead. As a
further security, the
calix was stamped
with the owner's name as well as the capacity. There are two specimens
of such
calices in the Roman Museums; one
in the Vatican, another in the Museo Kircheriano (Middleton, p. 455).
Pipes which had no
calix were termed
solutae. Frontinus also observes that
the velocity of the water passing through the
calix, and consequently the quantity given out, could be
varied according to the angle which the
calix made with the side of the reservoir: its proper
position was, of course, horizontal. (Frontin. 112, 113.)
It is evident how watchful an oversight must have been required to keep
the aqueducts in repair, to regulate their use, and to prevent the
fraudulent abstraction of their water. Under the republic, this office
was discharged by the censors (
Liv. 39.44),
and when there were no censors by the aediles (
Cic. Fam. 8.6); sometimes also by the quaestors (Frontin.
95, 96). Augustus first established the office of
curator (or
praefectus)
aquarum (Suet.
Octav.
37), to which he appointed M. Agrippa, who held the office till his
death in B.C. 12. A list of the
curatores
aquarum from Agrippa to Frontinus is given by the latter. They
were all of consular rank, and hence we find them called subsequently
consulares aquarum in place of their
ancient name. They were under the
Praefectus
urbi. The duties of the office are minutely described by
Frontinus (99), who seems, while he held the office, to have performed
it with the utmost zeal : among other cares, he had plans and models
made of the whole course of all the aqueducts (17, 64). The
curatores aquarum had under them a large number
of officials. They were attended outside the city by two lictors, three
public slaves, a secretary, and other attendants.
In the time of Nerva and Trajan, a body of four hundred and sixty slaves
were constantly employed under the orders of the
curatores aquarum in attending to the aqueducts. They
were divided into two families--the
familia aquaria
publica, established by Agrippa, and the
familia aquaria Caesaris, added by Claudius; and
they were subdivided into the following classes :--1. The
vilici, whose duty it was to attend to the pipes
and
calices. 2. The
castellarii, who had the superintendence of all the
castella, both within and without the city. 3.
The
circuitores, so called because they had to
go from post to post, to examine into the state of the works, and also
to keep watch over the labourers employed upon them. 4. The
silicarii, or paviours, who had to remove and
relay the pavement when the pipes beneath it required attention. 5. The
tectores, who had charge of the masonry
of the aqueducts. These and other workmen appear to have been included
under the general term of
AQUARII (Cod. 11, tit. 42 or 43, s. 10; Frontin. 116, 117.)
The following are the most important works on the Roman aqueducts
:--Frontinus,
de Aquaeductibus Urbis Romae, with the
notes and plates of Polenus, Patav. 1722; Fabretti,
de Aquis et
Aquaeductibus Veteris Romae; Stieglitz,
Archäologie der Baukunst; Hirt,
Geschichte d. Baukunst; Platner and Bunsen,
Beschreibung d. Stadt Rom; Becker,
Handbuch d.
Römischen Alterthümer, vol. i.; Canina,
Storia dell' architettura Romana; Jordan,
de
urbium Romae et Const. aquaed., Bonn, 1844; Parker,
Archæology of Rome; Burn,
Rome and
the Campagna. The most recent authorities are, Lanciani,
Topographia di Roma Antica, I Comentarii di Frontino,
Rome, 1880; Middleton,
Ancient Rome in 1885, pp.
451-476.
[
J.H.F] [
W.S]