Order as | Above Under
DATE. No. to Level. NAME. | ground. ground.
-----------+-------+--------+----------------+------------+-------------
| | | | _m._ _p._ | _m._ _p._
B.C. 312 | I. | 8th | AQUA APPIA | 0 60 | 11 130
| | | | |
” 263 | II. | 6th | ANIO VETUS | 0 221 | 42 779
| | | | |
” 145 | III. | 5th | AQUA MARCIA | 7 463 | 54 247½
| | | | |
” 126 | IV. | 4th | ” TEPULA | 7 0 | 6 0
| | | | |
” 34 | V. | 3rd | ” JULIA | 7 0 | 8 426½
| | | | |
” 21 | VI. | 7th | ” VIRGO | 1 240 | 12 865
| | | | |
” _c._ 10 | VII. | 9th | ” ALSIETINA | 0 358 | 21 714
| | | | | ? in channel
| | | | |
A.D. 33 | VIII. | 2nd | ” CLAUDIA | 10 176 | 36 230
| | | | |
” 33 | IX. | 1st | ANIO NOVUS | 9 400 | 49 300
-----------+-------+--------+----------------+------------+-------------
_Totals according to computation of Frontinus_ 42 918 242 692
------------------------------------------------------------------------
Of the above, six are carried to Piscinæ on the Via Latina.
{ V. JULIA }
The three { IV. TEPULA } carried from the same reservoir
{ III. MARCIA } on the same series of arches.
The two { IX. Anio Novus } carried on higher arches, which end
{ VIII. Aqua Claudia } after the Pallantian gardens.
The one II. Anio Vetus, has a reservoir on the
Via Latina.—(_Fron._, c. 19.)
SUPPLY.
As given in the Measured
No. Commentaries. at the head.
----------------+-------------+-------------+
| _quin._ | _quin._ |
I. APPIAN | 841 | 1825 |
| | |
II. ANIO VET. | 1541 | 4398 |
| | |
III. MARCIAN | 2162 | 4690 |
| | |
IV. TEPULAN | 400 | 445 |
| | |
V. JULIAN | 649 | 1206 |
| | |
VI. VIRGO | 652 | 2504 |
| | |
VII. ALSIETINE | —— | —— |
| | |
VIII. CLAUDIAN | 2855 | 4607 |
| | |
IX. ANIO NOV. | 3263 | 4738 |
| | |
----------------+-------------+-------------+
12,363 24,413
SUMMARY OF DISTRIBUTION.
Outside Inside No. of
No. City. the City. Regiones served. Castella.
----------------+---------+---------+-------------------------+---------
| _quin._ | _quin._ | |
I. APPIAN | 5 | 699 | II. VIII. IX. XI. XII. | 20
| | | XIII. XIV. |
| | | |
II. ANIO VET. | 573 | 1508½ | I. III. IV. V. VI. VII. | 35
| | | VIII. IX. XII. XIV. |
| | | |
III. MARCIAN | 261½ | 1472 | I. III. IV. V. VI. VII. | 51
| | | VIII. IX. X. XII. XIV. |
| | | |
IV. TEPULAN | 114 | 331 | IV. V. VI. VII. | 14
| | | |
V. JULIAN | 206 | 548 | II. III. V. VI. VIII. | 17
| | | X. XII. |
| | | |
VI. VIRGO | 200 | 2304 | VII. IX. XIV. | 18
| | | |
VII. ALSIETINE | 392 | —— | { Outside the city and | —
| | | { the XIV. in the |
| | | { Naumachia. |
| | | |
VIII. CLAUDIAN | 685 | | { United within the |
| | 3498 | { city, and distributed | 92
| | | { throughout the XIV. |
IX. ANIO NOV. | 728 | | { Regiones. |
| | | |
----------------+---------+---------+-------------------------+---------
3164½ 10,360½ 247
| DETAILS OF DISTRIBUTION.
|
| Imperial. Private. Public.
-------+----------+---------+---------
| _quin._ | _quin._ | _quin._
I. | 151 | 194 | 354
II. | 66½ | 490 | 503
III. | 116 | 543 | 439
IV. | 42 | 237 | 50
V. | 18 | 196 | 383
VI. | 509 | 338 | 1167
VII. | 354 | 138 | —
VIII. }| 1793 | 1506 | 1012
IX. }| | |
-------+----------+---------+---------
3049½ 3642 3908
| DETAILS OF THE PUBLIC SERVICE.
|
| Castra. Public Works. Munera. Laous.
-------+----+---------+----+---------+----+---------+-----+---------
| | _quin._ | | _quin._ | | _quin._ | | _quin._
I. | 1 | 4 | 14 | 123 | 1 | 2 | 92 | 226
II. | 1 | 50 | 19 | 196 | 9 | 88 | 94 | 218
III. | 4 | 41 | 15 | 41 | 12 | 104 | 113 | 253
IV. | 1 | 12 | 3 | 7 | — | — | 13 | 32
V. | 3 | 69 | 10 | 181 | 3 | 67 | 28 | 65
VI. | — | — | 16 | 1380 | 2 | 26 | 25 | 51
VII. | — | — | — | — | — | — | — | —
VIII. }| 9 | 149 | 18 | 384 | 12 | 107 | 226 | 482
IX. }| | | | | | | |
-------+----+---------+----+---------+----+---------+-----+---------
19 325 95 2312 39 394 591 1327
Buecheler, in his edition of Frontinus, pp. xi., xii., xiii., explains
the mathematical part of chap. 78 differently from Poleni and
Dederich[153].
In order to regulate these several aqueducts, so that deflection in any
part should be easily ascertained, means were provided for estimating
the abundance of the water, and in this respect for its minuteness and
clearness the treatise of Frontinus stands unrivalled, when compared
with any work of ancient or even modern times. The mode of measurement
is to take the area of a vertical section of the water flowing along
the _specus_,—the object being to test each aqueduct by itself, and to
see whether its proper supply was given or not. Had he been called upon
to estimate the actual supply of the water, and not the relative, other
points would have had to be taken into account, namely, the average fall
of the aqueduct, from which to gather its velocity. On this, however, he
does not touch. It must be borne in mind, also, that when Frontinus was
appointed, the system had been long in force, and he had to follow the
traditions and rules of his office. He made no revolution, he was simply
a reformer. He tells us that in examining the books belonging to the
office, he found certain measures given to certain aqueducts; these he
had to verify, and a great part of his work is taken up in the account
of his operations. To begin with, he is much troubled as to the measures
employed. The _digitorum modulus_ (i.e. a pipe with a given measured
orifice) is uncertain. There is the square digit and the round digit
(in other words, a square pipe of which each side is one digit, and the
round pipe of which the _diameter_ is one digit). As an instance of his
accurate and clear expression, it may be worth while to quote his words
on this point[154]:—
“The measurement of the _Moduli_ is taken either by digits or
inches. In Campania and in many places in Italy, the digit is
used; in Apulia, the inch[155]. The digit, as all agree, is the
sixteenth part of a foot; the inch, a twelfth part. But just as
there is a different usage of inches and digits, so also there
is no uniformity in the simple computation of the digit itself.
There is one which is called the square digit, another the
round digit. The square digit is _three-fourteenths greater_
than the round; the round is _three-elevenths smaller_ than the
square, because the angles are taken off.”
In this we obtain a key to most of his calculations[156], because they
depend throughout upon the computation of the area of the circle.
The base measure chosen was the “quinary,” so called (according to the
most natural derivation) because its diameter was five quarter-digits.
And to this basis are reduced some twenty different _moduli_, to which
the names were given of senary, septenary, octonary, denary, duodenary,
and so on up to centenary. The reduction of these seems to be tolerably
accurate according to the system which he pursues, and making allowance
for transcribers’ errors. But either the relation of the circumference
to the diameter of a circle had not been worked out to the same extent
to which it has been in later times, or Frontinus considered the ratio
adopted sufficient for his purpose. One of his calculations stands thus:
he is measuring the Appian at a point where it is joined by a later
branch; it had been assigned in the register as giving 841 quinaries: he
says—
“I found the depth of the water five feet, and its breadth one
foot and three quarters, which gives an area of eight feet and
three quarters. This is equal to twenty-two _centenaries_ and a
_quadragenary_, which make 1,825 _quinaries_, or 984 quinaries
more than is given in the Commentaries[157].”
Each centenary is shewn elsewhere to contain 81 quinaries and a fraction,
and therefore 22 would give 1,792 in quinaries and a fraction. The
quadragenary is marked to contain 32 quinaries and a fraction. Together,
therefore, the 1,825. Now the area of each quinary, according to the
system of Frontinus, would be the square of its diameter (i.e. 1¼ digit),
multiplied by ¹¹⁄₁₄ (the ratio already ascertained). This equals ²⁷⁵⁄₂₂₄,
which, multiplied by 1,825, produces 2,240½ digits (nearly). Finally, the
area of 8¾ square feet, reduced to square digits, gives 2,240[158].
This calculation illustrates his mode of computation from absolute
measure of the water; but the ordinary way was to affix the _moduli_,
which were of brass, or rather of bronze, to certain openings. Provided
the _modulus_ was placed perfectly level, the water flowed at its
ordinary rate; and when the _moduli_ were sufficient to prevent the water
rising in the reservoir or channel, and, on the other hand, not too
numerous or too large to reduce the mean level of the water, the sum of
them represented the amount of water.
We next come to the question of distribution. On examining the registers,
Frontinus says that he found that there were assigned to the nine
aqueducts 12,755 quinaries; but it appeared that the distribution
amounted to 13,470 quinaries. To account for this discrepancy, the whole
were re-measured. In the annexed table the measures of each aqueduct
are given separately, and by adding together the results of each, as
calculated from the data which Frontinus gives of the water measured at
the head, the total, as the table shews, comes to 24,413 quinaries. The
fact was that in process of time some of the channels had fallen into
decay, and the water was wasted. In other and more numerous cases, it
had been abstracted by persons for their own use without authority; in
addition to which there were no doubt errors in the computation, which
had crept into the books, and if we are to believe Frontinus, these
errors had been turned to the profit of his predecessors.
In the table of distribution will be seen the number of quinaries
distributed outside the wall of the city; next, the Regiones which they
serve within the city; thirdly, the measure of water so distributed
within the city, and the number of _castella_, or reservoirs, used
for that purpose. These reservoirs, at least such as remain, will be
described in the several Regiones in which they occur. That over the arch
of Dolabella on the Cœlian Hill, and the so-called Castellum Aquæ Juliæ
on the Esquiline, are the most prominent. Many, no doubt, were of much
smaller size, and merely large cisterns, as the total number was 247.
The supply of 13,470 quinaries is thus accounted for. Outside Rome 3,164
quinaries were distributed, inside 10,306; of that outside Rome 1,718
quinaries were used “in the name of the Emperor,” that is, to supply the
imperial villas and gardens, &c., while 2,345 were charged to private
persons. Inside Rome 1,707 were charged to the Emperor for his palaces,
&c., while private persons used 3,847 quinaries, leaving 4,401 quinaries,
which were for the “Public Service.” These, together, account for the
9,955 distributed within Rome.
In the details of the distribution, we learn how much water was employed
in the palaces, &c., in the service of the Emperor and his household
(_nomine Cæsaris_), how much was carried into houses for the use of
private persons, and how much was used in public buildings and the
public reservoirs or fountains which were established in all convenient
positions, and generally accessible to the population.
It may, perhaps, be interesting to examine more carefully the
distribution for the “Public Service.” We have four classes of
recipients, and we know from Frontinus how much was served to each class
from each aqueduct. There were first of all 19 _castra_ or barracks, in
which the army were kept when not out on service, and in which also the
guards were stationed. These required in all 279 quinaries. There were
next, 95 different Public Establishments which used 2,401 quinaries, and
39 theatres and places of entertainment (_munera_) which used 386 more.
Lastly, there were 591 open reservoirs (_lacus_) for the service of all
comers, using 1,335 quinaries. These reservoirs were what we usually
speak of as fountains, and some hundreds are in use to this day, many
probably on the site of the older ones. There were very stringent laws
respecting their use. Heavy penalties were inflicted upon anyone dipping
a dirty bucket or other vessel into the reservoir; there were also laws
respecting the “overflow,” as the fountains of course were constantly
running. These were the most important to keep in order, as all the
poorer classes depended entirely upon them for their supply of water.
The more wealthy had water brought into their own private reservoir in
the court, with buckets and windlasses for drawing the water to the upper
story, and this is the case to the present day[159].
These details, while giving us an insight into the social state of
the city, go to shew how thoroughly the supply of the water was
under control. The pipes supplying every one of these 744 points of
distribution were all registered, and their sizes being known, the system
of computation, as explained by Frontinus, was brought into play: thus
every part was checked, and any irregularity could be traced to its
source.
It may be asked what amount of supply, in gallons, would the water
represent, in order that a comparison can be made between the supply
of towns at the present time, and that of Rome at the time at which
Frontinus wrote. The answer is not easy. As said before, we have not
sufficient data for an accurate determination; still we may attempt an
approximate estimate. It is easy to compute the section of water given
by the 24,805 quinaries. This being just upon 120 square feet, we can
form some notion of the vast quantity, if we picture to ourselves a
stream twenty feet wide by six feet deep, constantly pouring into Rome
at a fall six times as rapid as that of the river Thames. It has been
computed by a French engineer that, together with one or two additional
aqueducts which were added between the time of Trajan and Aurelian, the
supply of water to Rome was 332,306,624 gallons _daily_. If we assume
the population to have been a million souls—and it is scarcely probable
that there were more—we find that the rate was 332 gallons per diem for
each person. In our own day we consider 40 gallons sufficient, and many
think this excessive, including the use of water in manufactures, &c. No
wonder, with the facilities for drainage which the rapid Tiber afforded,
and with this plentiful supply of really good water, the great city was
rendered, in spite of overcrowding and an unhealthy situation as regards
its neighbourhood, comparatively free from those epidemics which are so
fatal in all densely-populated towns.
One part of the system which Frontinus seems to have been the first to
adopt was this: he had 247 _castella_, or main reservoirs, from which
the pipes were carried to the smaller cisterns and fountains, and he so
arranged the supply of water to these that the several aqueducts could
be interchanged. A net-work was established, so that when one channel,
from whatever cause, failed, whether from requiring to be cleansed or
repaired, another could supply its place. But this was not all. He tells
us, cap. 87, that many of the parts of the city which were dependent on
one source for their supply, were, by careful distribution of the water,
able to avail themselves of a second in case of need; and he gives as an
instance that the Marcian was made available in the Aventine, by being
carried across from the Cœlian[160]. He also speaks of the improvements
which were made in keeping the water pure. Hitherto a very slight shower
had made many of the streams muddy, although at their source they were
pure[161].
The least pure, however, before the time of Trajan, were the Anio Vetus
and Anio Novus. This arose from the banks which, being soft, gave way,
and the stream, even in fair weather, thus became muddy. He points out
that hitherto, by the mixture of the waters which had been adopted to
prevent failure in supply, proper skill had not been shewn, and these new
streams were allowed to destroy the purity of others[162]. His object,
therefore, was to keep the pure streams separate, and in addition to
that, arrange that they should be used for drinking purposes only; while
the water which was less grateful to the taste, and which was subject to
be at times muddy, should be used for cleansing the city, or watering the
gardens, or other ordinary purposes, which it might fulfil equally with
the fresher and purer water. In considering the supply of water to our
large towns, which is one of the great problems which at the present time
has to be solved, it is not too much to say that—the plan adopted by the
Emperor Trajan, by the advice of Frontinus, the head of the _aquarii_,
and of that department of the government of Rome which had charge of
the aqueducts, the importance of which in that climate can hardly be
over-estimated—is worthy of more attention than it has received[163].
THE CURATOR AQUARUM.
The care of the aqueducts was assigned by Augustus to a Curator Aquarum,
of whom Marcus Agrippa was the first, and held the office for life.
Frontinus, to whom we are indebted (as we have seen) for nearly all
that we know respecting the early history of the aqueducts, held this
office under Domitian, A.D. 94; he remained in office under Nerva, wrote
his treatise at that time, and died under Trajan, A.D. 107. The office
continued to exist till the third century, in the time of Diocletian,
when it was superseded by the magistrates called _Consulares Aquarum_,
a title changed in the fifth century into _Comes Formarum Urbis_. These
several magistrates had 700 servants, charged with the superintendence,
repair, and distribution of the water from the aqueducts, divided into
_familia publica_ and _familia Cæsaris_; the former, comprising 240
persons paid by the State; the latter, 460 paid by the Emperor. Agrippa
supplied the city with 700 _lacus_, 105 fountains, 130 _castella_ for
distributing waters, and 170 gratuitous baths for public use. These
structures were adorned with 400 marble columns, and 300 statues of
marble or bronze. After the devastations caused in the Gothic wars, under
Vitiges and Totila, only the most important aqueducts were restored,
either by Belisarius or Narses. Ruin and neglect again undid much of what
had then been restored to use. At the beginning of the ninth century, the
only aqueducts supplying water were the Appian [I.], and Marcian [XII.],
then called Jobia or Iopia, by corruption from “Jovius,” the name assumed
by Diocletian.
During both the eighth and ninth centuries, indeed, various repairs for
maintaining the aqueduct of Trajan [X.], which carried water from the
lake Sabatinus (di Bracciano, Acqua Paola), are mentioned by Anastasius;
and in 786 the “Jovia” aqueduct was restored by Hadrian I. In the twelfth
century, the Aqua Lateranensis is mentioned as still in use, being that
part of the Claudian aqueduct carried upon the arcade called the Arches
of Nero near the Lateran, where the _specus_ is very conspicuous. The
aqueduct of Trajan [X.], and that of Agrippa [VI.], continued to supply
water, though but scantily, for about two centuries later. The Appia [I.]
has long been supposed to have been gradually stopped up by the deposit
of clay, and thus rendered useless[164]; and so total was the failure of
all these waters in the fourteenth century, that the population (said
to have been not more than 17,000 during the absence of the Papal Court
at Avignon) were without any supply of running water, except from the
Tiber[165]. The first restoration, in the fifteenth century, was that of
Agrippa [VI.], by Nicholas V., whose aims and efforts were renewed by
Sixtus IV., and by later Pontiffs. Sixtus V. [Felice Peretti] determined
to restore to Rome the water then supposed to be the Marcia, but really
of Hadrian [XIII.] The arcade of the Claudian [VIII.] and Anio Novus
[IX.], was the most magnificent of all, and conveyed its several streams
along a distance of forty-six miles. This had been restored by Vespasian
and Titus, by Trajan, Septimius Severus and Constantine; but, in the
greater part, especially within the first few miles from Rome, the
existing stone arcade is of the time of Claudius, with repairs in the
brickwork of the Flavian emperors. At the beginning of the ninth century,
it was certainly still serviceable, and was known by the name Forma
Claudiana. The piers of this arcade were used by the engineers of Felice
to carry that _specus_ on the part near Rome; but the greater part of the
Marcian arcade, and considerable parts of the Claudian, near Rome, were
used as a stone-quarry by them. The channels through which the Anio and
the other streams flowed, were the first, 9 ft. in height and nearly 3
in breadth, the second 6 ft. by 3, as seen in their ruins at the Porta
Maggiore. The more ancient portion is not in brickwork, but of enormous
squared blocks of tufa and peperino.
The popular notion that all these aqueducts were a mere waste of money,
arising from the ignorance of the ancient Romans of the simple fact
that water will rise to its level, is altogether erroneous. Vitruvius
gives directions for taking the levels for carrying water through
valleys, where, he says, there should be standing or upright pipes
(_columnaria_,), now called respirators, to let off the confined air
(_spiritus_[166]), and explains how to bring the water on by earthenware,
lead, and even leather pipes.
Within the last few years a large leaden pipe of great antiquity, not
less than two feet in diameter, was found under the Via de’ Condotti,
encased in ancient brickwork, evidently shewing that they were afraid
to trust to the strength of the lead. The force of the water running in
a strong current from such great distances, required to be broken at
frequent intervals, by being turned at a sharp angle, and then allowed
to return again to its course by another angle. This arrangement occurs
continually along the line of the aqueducts, generally at each half mile,
with a _piscina_ or a _castellum_, or both filtering-place and reservoir,
at each of these angles. The great object of constructing these
magnificent aqueducts was to bring the water to the highest levels in the
city, from which it descended by a succession of reservoirs (_castella
aquarum_), some with _piscinæ_ or filters, others with fountains, each
one below the level of the preceding one. The lower town along the
valley, or Campus Martius, was also supplied by other aqueducts at a much
lower level. The ancient Romans had abundance of leaden pipes to convey
the water to the baths or _thermæ_, and bronze stop-cocks, as may be seen
at Pompeii, and silver ones for the emperor; but they had no pumps. From
each _castellum_ there were pipes to supply the neighbouring baths or
palaces, with moderate pressure; also wells or cisterns in the courtyard
of each house, which had frequently a fountain. On the Janiculum, the
water of the aqueduct passing from one _castellum_ to another, has
sufficient force to turn several mill-wheels.
A letter of King Theodoric, printed in Cassiodorus[167], addressed to the
Roman Senate, enjoins them to assist Joannes in his enquiries after those
who have diverted the water from the aqueducts for their own uses, and
those who have stolen the brass and lead, or those who have helped them.
This proves that they were not destroyed by the Goths, and that they were
in use in the sixth century.
CHAPTER IV., PART II.
THE LATER AQUEDUCTS.
X. SABATINA, A.D. 110; TRAJANA AND PAOLA, A.D. 1540.
The Aqua Sabatina came from the springs which supply the lake Sabatinus,
now called di Bracciano (in the Middle Ages it was, and is still often
called, Anguillara), on the side opposite to Rome, about twenty-four
miles from the city, in a tunnel at a considerable depth. It arrives at
the line of the tunnel of the Aqua Alsietina in about three miles. (See
Aqueduct VII.)