of water from the small lake called the Lago di S. Lucia, which is
nearer to Rome, and which they had been misinformed was the Aqua Marcia.
Dr. Fabio Gori, from his great local knowledge and his archæological
researches, was able to shew that this was a mistake, and wrote to that
effect a letter in the Roman newspaper called the _Osservatore Romano_.
This letter at first gave great offence, and a very warm controversy was
carried on for some time on that subject. Eventually, however, a new
engineer of the company thought it better to examine the ground himself,
and the result was to establish that Gori’s views were perfectly correct.
He then became a warm advocate for the company, which he thinks entitled
to great praise for the admirable manner in which its works in the valley
of the Anio have been carried out as far as Tivoli. Their works almost
equal those of the time of the Empire, and are carried out on the same
principles; but from Tivoli to Rome the water is carried in metal pipes,
and not in a stone _specus_ as it is above Tivoli. This enables the
company to carry it in a more direct line.
[80] See the Appendix to this Section.
[81] A great deal too much importance has been attached to this Cyclopean
Masonry, _Opus Cyclopæum_. See the Chapter on the Construction of Walls.
[82] It is probably the case that part of this supply was brought in
metal pipes only, from the evidence of this inscription. A stone _specus_
passes under the wall on the bank round three sides of the camp on the
exterior of the walls, and is plainly visible at the north-east corner;
but this agrees with the general character of the Anio Vetus, and was
probably a branch from that aqueduct.
The inscription is as follows:—
IMP. CAES. M. OPELLI . SEVERI . MACRINI
. AVG
M. OPELLI . SEVERI . DIADVMENIANI .
CAES. PRINC. IV
CASTRIS . PRAETORI
TERENTIVS . CASSANDER . FECIT
[83] “[Honorius, Papa III.] Ecclesiam Sanctæ Bibianæ juxta formas aquæ
Martiæ cum Monasterio Monialium restituit.” (Ciaconi, Vitæ Pontif.
Roman., &c., vol. ii. col. 46, C.)
[84] An inscription recording repairs by Agrippa is said by Ligorio to
have been found on a _cippus_ of travertine at the third mile on the
Via Latina. The genuineness of this is doubted by Fabretti, because the
number of miles does not agree; but it seems more probable that this was
an error in transcribing, than that the inscription should be forged
without any motive for doing so:—
AQVAE . IVLIAE . TEPVLAE.
IMP. CAES. DIVI . IVLI . F.
AVGVSTVS . PONTIF.
MAX. COS. X̅I̅I̅. TRIB. POT.
X̅I̅X̅. IMP. X̅I̅I̅I̅. CVRANTE
M. VIPSAN . AGRIPPA .
AEDIL . CVRVL . L. C. C.
P. MILL. X.
Another inscription, also recording repairs of the time of Augustus, was
found by Fabretti himself, in the Vinea Bartholomæi Virginii, two miles
from the Porta Maggiore, between the ruins of the arcades of the Marcian
and Claudian, and was preserved in a private museum:
IVL. TEP. MAR.
IMP. CAESAR.
DIVI . F.
AVGVSTVS.
EX. S. C.
LXIII.
P. CCXI.
[85] _Marrana_ is a general name for a running stream in the Campagna
round Rome, probably a provincial word; but it is also the special name
of this particular stream coming from Marino.
[86] “Tepula concipitur via Latina ad decimum milliarium, diverticulo
euntibus ab Roma dextrorsus millium passuum duum ... inde suo rivo in
urbem perducebatur.” (Frontinus, c. 8.)
[87] It is the building pointed out in guide-books as “The House of
Cicero,” although there does not appear to be any historical ground for
this name.
[88] “... ad milliarium ab urbe duo-decimum via Latina, _diverticulo_
euntibus ab Roma dextrorsus millium passuum duum alterius aquæ proprias
vires collegit et Tepulæ rivum intercepit. Acquisitæ aquæ ab inventore
nomen Juliæ datum est, ita tamen divisa erogatione, ut maneret Tepulæ
appellatio.”—(Frontinus, c. 9.)
[89] “Præter caput Juliæ transfluit aqua quæ vocatur Crabra. Hanc Agrippa
omisit.”—(Frontinus, c. 9.)
[90] Pag. clxxxii. 8, “In tubulo plumbeo reperto ad portam S. Laurentii,”—
P. CORNELIO . DOLABELLA . C . IVN . SILANO . COS—AQVA . MAR
[91] Gruter, pag. clxxxiii. 4,—
Q. AQVILLIO . SABINO . II.
SEX . AVR . ANVLLINO
CASTR . PRÆT . L. VRBIS . OFF . PED .
COS . CCCLXXXIII.
AQVA . MARC
[92]
HAC RIVI AQVAR
TRIVM EVNT CIPPI
POSITI IVSSV
A. DIDI. GALLI
T. RVBRI. NEPOTIS
M. CORNELI FIRMI
CVRATORVM AQVAR
[93] Frontinus, c. 10.
[94] “Concipitur Virgo via Collatia ad milliarium octavum palustribus
locis, _signino circumjecto_ continendarum scaturiginum causâ.”
_Signinum_ is the particular kind of cement to hold water, always used
to line the walls of the Aqueducts. It was not used after the time of
the Empire, and the art of making it is said to be lost. It is the usual
characteristic of the remains of an aqueduct.
[95] Frontinus, c. 10.
[96] Ibid., c. 22.
[97] This water is now usually called Acqua di Trevi, because its
terminus is at the great fountain of Trevi. The sources are in the
estate of Salone, as above described. It is still in use, and was long
considered as the best water brought into Rome. The line now used is
the one repaired and restored by the Popes; but, near Rome, it has been
altered, probably after it had been damaged by the Goths or the Lombards.
The old _specus_ passed through the Catacomb of S. Priscilla, in the Via
Salaria, where it may be seen. This is demonstrated by the _cippus_ of
the aqueduct of Virgo, discovered in the Via Salaria, and so recorded by
Muratori, Thes. Vet. Inscr., ccccxlii. 7, “Romæ in Via Salaria:”—
VIRG.
TI . CÆSAR . AVG.
PONTIF . MAXIM.
TRIB. POT. XXXVIII.
COS . V̅. IMP. V̅I̅I̅I̅.
I.
P. CXL.
This inscription is A.D. 36.
It was then brought to the bank or _mœnia_ on which the wall of Aurelian
was afterwards built near the Porta Salaria, and may be traced upon or in
that bank under the present wall of Rome for about a mile. For a short
distance, where this ground is low, it was carried on an arcade, of which
there are remains under the wall built upon it. After this it goes on as
far as the garden of the Villa Borghese and the French Academy, under
which it now passes through the Pincian Hill.
[98]
TI . CLAVDIVS . DRVSI . F. AVG. GERMAN. PONT.
MAX. TRIBVNIC. POT. V. IMP. IX. P.P. COS. III.
DESIG. IIII. ARCVS . DVCTVS . AQVÆ . VIRGI
NIS . DISTVRBATOS . PER . C. CÆSAREM . A. FVN
DAMENTIS . NOVOS . FECIT . AC . RESTITVIT
This inscription was erected A.D. 46.
[99] There are remains of the Septa in the cellars under the houses on
the west side of the Corso, in its lower part. These remains of the
arcade are now chiefly underground, owing to the filling up of the great
foss, called in this part Via Lata, because the wide foss under part of
the Quirinal and of the Capitol had at one time been made into a wide
street or place, on the eastern side of which is situated the Church of
the “SS. Apostoli in Via Lata” and that of S. Maria in Via Lata on the
western side, at the north-west corner. The great public building called
the Septa went down the western side of this wide place from S. Maria to
the Venetian Palace, with an arcade towards the street or place, of which
many of the arches remain in the cellars. These arches under the church
of S. Maria are absurdly called the house of S. Paul. They are visible
also under the Palazzo Doria to the south of that church, and in other
cellars.
[100] “Idem et Virginem adduxit ab octavi lapidis diverticulo duobus
millibus pass. Prænestina Via.
“Juxta est Herculaneus rivus quem refugiens Virginis nomen obtinuit.”
(Plinii Nat. Hist., lib. xxxi. c. iii. § 25.)
[101] Of this stream and its introduction into Rome in the twelfth
century, an account will be found in the second part of this chapter.
Frontinus, c. 15 and 19.
[102] Frontinus, c. 11.
[103] Ibid., c. 18.
[104] Ibid., c. 71.
[105] The draining of the lakes in the hills round Rome is a great
mistake, and very injurious to the health of the city. Such lakes are a
wise provision of nature for collecting some of the surplus water in the
rainy season, and preserving it for use in the hot and dry season, when
the evaporation from the lakes helps to cool the air. The water also
drawn from these lakes was most useful for the irrigation of the country
round Rome, and watering the gardens in Rome itself, thereby promoting
vegetation, which is essential for health in a hot and dry climate. It
is well known that the leaves of plants and trees (more especially of
deciduous trees) absorb _nitrogen_, which is the part injurious to human
life, and give out _oxygen_, that portion which is beneficial to, and
necessary for, human life. Where there is no vegetation, therefore, the
climate cannot be healthy, and without water there can be no vegetation;
for water is the necessary food of plants.
[106] The line of this subterranean aqueduct can also be traced by the
wells descending into the _specus_, in the same manner as the Aqua Appia
was traced in 1870, that is, by the bushes growing at the top of each of
the wells, and generally enclosed by a wooden railing to prevent animals
from falling into them.
[107] The rock in which the tunnel is cut is a sort of peperino, hard and
rough, covered with a bed of clay.
[108] This lake, called Sabatina in the time of Frontinus, was called
Anguillara in the Middle Ages, and is now called Bracciano, in both cases
from the names of the proprietors. The great family of Anguillara had
their origin from this village, of which they were the proprietors, and
where they had a castle on the bank of the lake. The present proprietors
are the Dukes of Bracciano. The lake produces a great abundance of fish,
especially a small fish much resembling the white-bait of London, at
least when cooked.
[109] There is a small construction over this flood-gate, and at the back
of it is this inscription:—
ACQVA PAOLA
ALLA PRESA DELL’ ACQVA
ALSEATINA
[110] There are interesting remains of the Necropolis of this ancient
city close to the fountain before mentioned, on each side of a deep
ravine. On one side, there are nine chambers cut out of the rock on the
edge of the cliff, the entrance being in the central chamber, with four
others on either side of it. All are full of small square _columbaria_,
of very early character. On the opposite side of the ravine, is a similar
series of tombs, but in a less perfect state.
[111] There is _Opus Reticulatum_ of rude and early character (more like
the _Opus Incertum_ of the Emporium than the mausoleum of Augustus) at
the entrance of this passage, which is mentioned by Nibby. There is a
stone-quarry also at the entrance, of the hard, dark-coloured stone used
for making roads, and excellent for that purpose. This is the same stone
that is called _selce_ or _silex_ in Rome, and seems to be similar to
the hard lava under which Herculaneum is buried, and of which there are
quarries near the tomb of Cecilia Metella.
[112] The persons employed by Mr. Parker went down to the bottom of this
steep tunnel-passage to ascertain this.
[113] Nibby, Analisi storico-topografico-antiquaria della carta de’
Dintorni di Roma, tom. i. Roma, 1837, 8vo. art. _Alsietina_.
[114] Cassio, Corso delle Acque, vol. i. p. 147.
[115] Nibby considers this a mistake, and is of opinion that the water
was the Sabatina, not the Alsietina; but the mistake is made by Nibby
himself, not by the engineers of Pope Paul, who certainly brought the
water from the Lacus Alsietina and the other small lake above it (as
mentioned on p. 50). By the draining of these lakes, the aqueduct is
_now_ made to depend on the Lacus Alsietina only. The sources of the
Alsietina are very different from those of the Sabatina. The former
was taken by Augustus from the lake Alsietinus, now called Lago di
Martignano, and the latter by Trajan from the sources between the lake
Sabatinus and the villages of Vicarello, Bassano, and Oriolo. The
Alsietina was at the lowest level of all the aqueducts, and the Sabatina
at the highest. The first _specus_ was for the most part subterranean,
and the other was carried upon arcades for part of its course.
[116] By the more usually received computation, the second year of
Caligula would be A.U.C. 791; and the year of the consulship of Sulla and
Titian, A.U.C. 805.
[117] It surpassed all the others _in quantity_, and being the highest,
was used to supply the others when the water fell short; but the water
was not so good for drinking.
[118] Frontinus, c. 13.
[119] That is, higher than any other aqueduct.
[120] Frontinus, c. 20.
[121] The road to Subiaco.
[122] Frontinus, c. 14.
[123] Ibid.
[124] Ibid.
[125] Ibid., c. 18.
[126] _In Subruino_ is the reading given in the text by Dederich. _In suo
rivo_ is the reading adopted by Polenus, Jocundus, and other editors. A
third reading has been suggested, “In Simbrivio,” or in Simbruino, that
is, referring to the Simbruine hills. This is the reading of Buecheler
(1868), who follows verbatim the manuscript of Monte Cassino. The
reading, however, bears little upon the evidence.
[127] _Herculaneus Rivus._ This is not the same _Herculaneus Rivus_ as
the one mentioned by Frontinus in connection with the Anio Vetus, in ch.
19. The same name is given in these places to different streams, all
strong and rapid.
[128] Frontinus, c. 15.
[129] Ibid., c. 93.
[130] Ibid., c. 91.
[131] Frontinus, c. 76.
[132] “At ex alia parte Anio in monte Trebanorum ortus lacus tres
amœnitate nobiles, qui nomen dedere Sublaqueo defert in Tiberim.” (Plinii
Nat. Hist., iii. 109.)
[133] The inhabitants of Filettino probably belonged to the tribe of the
Trebani, or of Trebula, who were located in the neighbourhood of Trevi,
where was a Roman colony and principality. Inscriptions giving the names
and titles of Augustus, Septimius Severus, and Commodus, were found here,
and are published by Signor Gori in his Trattato dell’ Acqua Marcia, &c.,
12mo., 1866, p. 37. Another inscription at Anagni, on the front of the
Governor’s palace, gives the name of Publius Vecellius, curator of the
Republic of the Trebani.
Martial mentions the Treba Augusta of Frontinus, under the name of
Trebula:
“Trebula nos genuit, commendat gratia duplex Sive levi flamma, sive
domamur aqua.” (Lib. v. epigr. 65, and lib. xiii. epigr. 33.)
Livy also mentions it: “Eodem anno Arpinatibus Trebulanisque civitas
data.” (Livii Hist., x. 1.)
[134] IMP CAESARIS NERVAE TRAIA(_ni_) ... OP(T)IMI AVG GERMANIC DACICI.
[135] “Lacus monasterii ad nihilum redactus, quia duo monachi levaverunt
duo lapides, qui fuerunt firmati cum aliis petris; et sic aqua
destruxit.” (Chronicon Sublacense, apud Muratori, Rer. Ital. Script.,
tom. xxiv. col. 962, D.) The author of this Chronicle was living in the
year 1390.
[136] Gruter, Inscriptiones, p. clv. 4.
[137] Probably the text of Frontinus here is corrupt, because the Piscina
Limaria and the _specus_ of Claudius are at the forty-sixth mile on
the Via Sublacensis, “ad milliarium quadragesimum _secundum_,” for “Ad
milliarium quadragesimum _sextum_.”
[138] Dr. Fabio Gori, who is a native of Subiaco, claims the credit of
being the first person to point out what this great work of Trajan really
was. He also states that the Rivus Herculaneus, rising at thirty-eight
miles on the Via Sublacensis, must have been a clear stream, which he
finds on the left side of the river, opposite to the lake of S. Lucia and
to this source of the aqueduct of the Claudia, called Acqua dell’ Arco,
or water of the aqueduct.
[139] Frontinus, c. 72.
[140] The _piscina_ made in one of the towers in the wall at the point
where it enters Rome, has the four chambers visible, the inner wall of
the tower having been destroyed.
[141] Inscriptions on the Porta Maggiore:—
TI . CLAVDIVS DRVSI F. CAISAR AVGVSTVS
GERMANICVS PONTIF MAXIM
TRIBVNICIA POTESTATE X̅I̅I̅. COS. V.
IMPERATOR X̅X̅V̅I̅I̅. PATER PATRIÆ
AQVAS . CLAVDIAM EX FONTIBVS . QVI
VOCABANTVR CAERVLEVS ET CVRTIVS
. A MILLIARIO X̅X̅X̅X̅V̅.
ITEM ANIENEM NOVAM A. MILLIARIO
L̅X̅I̅I̅. SVA IMPENSA IN VRBEM PERDVCENDAS
CVRAVIT.
IMP . CAESAR . VESPASIANVS AVGVST .
PONTIF . MAX . TRIB. POT. I̅I̅. IMP.
V̅I̅. COS. I̅I̅I̅. DESIG. I̅I̅I̅I̅. P.P
AQVAS CVRTIAM ET CAERVLEAM PERDVCTAS
A DIVO CLAVDIO . ET POSTEA
INTERMISSAS DILAPSASQVE
PER ANNOS NOVEM . SVA IMPENSA
VRBI RESTITVIT.
IMP . T. CAESAR DIVI F. VESPASIANVS
AVGVSTVS PONTIFEX MAXIMVS . TRIBVNIC
POTESTATE X. IMPERATOR X̅V̅I̅I̅. PATER
PATRIAE . CENSOR . COS . V̅I̅I̅I̅.
AQVAS CVRTIAM ET CAERVLEAM PERDVCTAS
A DIVO CLAVDIO ET POSTEA
A DIVO VESPASIANO PATRE SVO VRBI
RESTITVTAS . CVM A CAPITE AQVARVM
A SOLO VETVSTATE DILAPSAE
ESSENT . NOVA FORMA REDVCENDAS
SVA IMPENSA CVARVIT. (Orelli, vol.
i. p. 77, Nos. 54-56.)
These inscriptions shew that considerable repairs were made by Vespasian
and Titus to the Claudian aqueducts; and these repairs were continued by
their successors, Nerva, Trajan, and Hadrian. Many parts and branches
belong to the time of these Emperors.
[142] Vide “Delle vere Sorgenti dell’ Acqua Marcia,” &c., “trattato di
Fabio Gori.” Roma, 1866. An admirable map shewing the sources and the
line of each of the Aqueducts, has been made for me under the direction
of the author.
[143] Frontinus (c. 15) gives the length of the _specus_ of the Anio
Novus as 58 miles and 700 _passus_; add to this the length of the Piscina
Limaria and of the three lakes, and we have the distance of 62 miles from
Rome for this aqueduct.
[144] “Qui colles, (mons Cœlius et Aventinus,) priusquam Claudia
perduceretur, utebantur Marcia et Julia. Sed postquam Nero Imperator
Claudiam, opere arcuato altius exceptam, usque ad templum Divi Claudii
perduxit, ut inde distribueretur, priores non ampliatæ, sed omissæ sunt:
nulla enim castella adjecit, sed iisdem usus est, quorum, quamvis mutata
aqua, vetus appellatio permansit.” (Frontinus, c. 76)
[145] The large square part of the Cœlian Hill, with scarped cliffs
round three sides of it and part of the fourth, which had probably been
originally the _arx_ or citadel of the Cœlian when that was a separate
fortress, and on which Claudius erected some great public building with a
temple, is marked on the modern maps of Rome as a _castellum aquæ_: this
is an exaggeration. A _specus_ runs along the western side opposite to
the Palatine in the wall, and goes straight towards the Colosseum, and
there are remains of a piscina of the first century at the north-west
corner of the Claudium, near the Colosseum, and the Meta Sudans; but this
is at a low level, and does not agree with there being a large reservoir
under the whole of that space.
[146] Frontinus did not live to see this completed.
[147] Cap. 86, 91, 92, and 105.
[148] These are at present almost hid by modern houses built up against
them, but it is expected that these modern erections will shortly be
removed. The remains of the bridge project at a right angle from the
palace of Domitian. It had the aqueduct at the top at a very high level,
and a road for horses by the side of it at a lower level, as at the Ponte
Lupo, Ponte S. Antonio, and other bridges of the aqueducts.
[149] These imperial “Edicts” or “Decrees,” or Laws and Constitutions,
have been published in various works. The later ones relating to this
subject are published by Polenus, in the Appendix to his edition of
Frontinus, 4to. Pataviæ, 1722; and by Rondelet, as a supplement to
Frontinus, who had published those issued up to his time. See Commentaire
de Frontin sur les aqueducs de Rome, 2 parts, 4to. and atlas folio,
Paris, 1802; and Rondelet, Opere, 6 vols. 4to. Mantova, 1841, tom. vi. p.
117, &c.
[150] This water was celebrated for its coolness, as mentioned in the
life of Alexander Severus by Lampridius, c. 30.
[151] The new company for bringing these springs into Rome again, under
the name of the Aqua Marcia-Pia, has been obliged to make compensation
to the town of Tivoli for the possible injury to the manufactories
established there, which depend upon the force of the water, although
the damage was in a great degree imaginary. This new aqueduct brings the
water of the Marcia only. The water is nearly of the same quality as
that of the Claudia, and is still found as cool as it was in the time of
the early Empire, notwithstanding that it is brought into Rome in metal
pipes for the last ten miles. A number of shops for the sale of this
cool water have been opened in different parts of Rome. Nature never
changes, and the same qualities of particular springs which prevailed
two thousand years ago, prevail still. It is said by persons who have
witnessed the experiment tried, that in the hot summer weather of Italy,
when the thermometer of Fahrenheit stands above 100, the contrast between
the heat of the air and the coldness of the water is so great that if a
glass tumbler is suddenly put into the water near its source, the glass
will break in the same manner as a glass tumbler will break in England if
boiling water is poured into it in frosty weather.
[152]
In the above the _m_ = to the Roman mile = 1,000 Roman
passus.
_p_ = to the Roman passus = 5 Roman feet.
The Roman mile (_mille passus_) = 1,618 English yards.
The Roman passus = 4 English feet 10·428 inches.
The Roman foot = 11·6496 English inches.
[153] The Roman foot was nearly as long as our own, being, according to
the most accurate estimate, about 11½ English inches (11.6496).
[154] Frontinus, c. 24.
[155] Dederich reads “unciæ in popularibus rationibus adhuc observantur,”
which seems better. The _uncia_ was an Italian, the _digitus_ a Greek
measure.
[156] It is evident from his making the square of the diameter ³⁄₁₄
greater than the area of the circle drawn upon the same diameter, that he
takes the ratio of the area to the diameter as ¹¹⁄₁₄ to diameter 1. This
is very near to the truth. The converse as given by him also agrees, as
is seen by ¹¹⁄₁₄ + ³⁄₁₁ of ¹¹⁄₁₄ = 1.
[157] Frontinus, c. 65.
[158] It is of little consequence, but perhaps it may be interesting to
know more accurately the result of the calculation. If we take 1.25 as
the diameter of the quinary, and multiply the square of this by 0.7854
(the corrected ratio), we obtain the result in square digits, 1.22718.
This multiplied by the 1825 gives 2239.6, that is, the result within one
digit as given by Frontinus.
[159] An Anglo-Roman company has now (1872) brought the Aqua Marcia
(III.) again into Rome at so high a level, that it will supply cisterns
at the tops of the houses. At present a number of ingenious contrivances
are in use for sliding small buckets of water from the well or reservoir
in the courtyard, to the upper windows and galleries round the central
courts of the old houses or palaces. These reservoirs, whether large or
small, are called _lacus_ by Frontinus and in the Regionary Catalogue.
[160] The expression _reddita_ would imply that originally the Marcian
had supplied the Aventine, and that, it having been superseded by the
Claudian, it was now restored and used in addition to the other. See the
extract—Frontinus, c. 76.
[161] Frontinus, c. 89.
[162] Ibid., c. 90, 91.
[163] The division of the surface water from the sewerage, in the
question of the drainage of large towns, is meeting with much favour,
as it appeals to reason that what is good for the purposes of manure,
is destructive to the healthy condition of the river, while the surface
water, which finds its proper place in the river, interferes with the
proper distribution of sewage. In Rome, there is frequently a small
_specus_ or channel for pure water, contrived in the vault or upper part
of the great _cloacæ_ or drains for the refuse water. Could not the same
plan be adopted in London with advantage? But while this is canvassed,
it seems singular that we hear little of the division of the _supply_,
which, on the same principle, should certainly be divided. There are
several towns so situated, that a fair supply of pure water might be
brought very acceptable for drinking, but not in sufficient quantities to
be applicable to other offices. The words of Frontinus are very concise
and pointed:—
“Marciam ut ipsam, splendore et frigore gratissimam, balneis ac
fullonibus et relatu quoque fœdis ministeriis deprehenderimus servientem.
Omnes ergo discerni placuit, tum singulas ita ordinari, ut in primis
Marcia potui tota serviret, et deinceps reliquæ secundum suam quæque
qualitatem aptis usibus assignarentur, sicut Anio Vetus pluribus ex
causis, quo inferior excipitur minus salubris, in hortorum rigationem
atque in ipsius urbis sordidiora exiret ministeria.” (Frontinus, c. 91,
92.)