Encyclopaedia Britannica > Volume 3, Anatomy-Astronomy

AQUEDUCT.
Aqueduct, waters. The branch seen in elevation extends 670 feet
'~-^v^>'in length, and is 106 feet in height at the deepest part.
It is composed of three rows of arches, those in each row
increasing in width from the bottom to the top—an ar¬
rangement very properly introduced with the view of
saving materials without diminishing the strength of the
work. The two upper rows consisted of arches of semi¬
circles, the lower of Gothic arches ; and this circumstance
serves to fix the date of the structure, as these last were
not introduced until the 10th century. The breadth of
the building at the base was 21 feet, and it diminished
with a regular batter on each side to the top, where it
was only 11 feet. The base also was protected by strong
buttresses or counterforts, erected against each of the
pillars. The other branch of the aqueduct was 300 feet
long, and consisted of 12 semicircular arches.
This aqueduct serves to convey to Constantinople the wa¬
ters of the valley of Belgrade, one of the principal sources
from which the city is supplied. These are situated on the
heights of Mount Haemus, the extremity of the Balkan
Mountains, which overhangs the Black Sea. The water
rises about 15 miles from the city, and between three and
four miles west of the village of Belgrade, in three sources,
which run in three deep and very confined valleys. These
unite a little below the village, and then are collected into
a large reservoir. After flowing a mile or two from this
reservoir, the waters are augmented by two other streams,
and conveyed by a channel of stone to the Crooked Aque¬
duct. From this they are conveyed to another, which is
the Long Aqueduct; and then, with various accessions,
into a third, termed the Aqueduct of Justinian. From this
they enter a vaulted conduit, which skirts the hills on the
left side of the valley, and crosses a broad valley two
miles below the Aqueduct of Justinian, by means of an
aqueduct with a double row of arcades of a very beauti¬
ful construction. The conduit then proceeds onward in
a circuitous route, till it reaches the reservoir of Egri
Kapan, situated just without and on the walls of the
city. From this they are conducted to the various quar¬
ters of the city, and also to the reservoir of St Sophia,
which supplies the seraglio of the grand signior. The
Long Aqueduct is more imposing by its extent than the
Crooked one, but is far inferior in the regularity of de¬
sign and disposition of the materials. It is evidently a
work of the Turks. It consists of two rows of arcades,
the lower being 48 in number, and the upper 50. The
whole length was about 2200 feet, and the height 80
feet. The Aqueduct of Justinian is a very excellent work,
and without doubt one of the finest monuments which
remain to us of the middle ages. It consists of two rows
of large arcades in the pointed style, with four arches in
each. Those of the lower story have 52 feet of span,
the upper ones 40 feet. The piers are supported by
strong buttresses, and at different heights they have little
arches passing through them, which relieve the deadness
of the solid pillar. The length of this aqueduct is 720
feet, and the height 109 feet. This aqueduct, though it
bears the name of Justinian, was probably erected in
the time of Constantine.
Besides the waters of Belgrade, Constantinople was sup¬
plied from several other principal sources, one of which took
its rise on the heights of the same mountains, three or
four miles east of Belgrade. This was conveyed in a simi¬
lar manner by an arched channel, elevated when it was
necessary on aqueduct bridges, till it reached the northern
parts of the city. It was in the course of this aqueduct
that was constructed the contrivance of the souterasi or
hydraulic obelisks described byAndreossy, and which has
excited some attention, as being an improvement on the
method of conducting water by aqueduct bridges. “ The
335
souterasi, says Andreossy, “are masses of masonry, having .
generally the form of a truncated pyramid or an Egyptian
obelisk. To form a conduit with souterasi, we choose
tbanTh °f Water’. t}|f le';e.1 of which is several feet higher
the c.tv reyvrV“ir. by which it is to be distributed over
he city. We bring the water from its sources in sub-
erranean canals, slightly declining until we come to the
borders of a valley or broken ground. We there raise
on each side a souterasi, to which we adapt vertically
leaden pipes of determinate diameters, placed parallel to
the two opposite sides of the building. These pipes are
disjoined at the upper part of the obelisk, which forms a
sort of basin, with which the pipes are connected. The
one permits the water to rise to the level from whence
it had descended; by the other, the water descends from
this level to the foot of the souterasi, where it enters
another canal under ground, which conducts it to a se¬
cond and to a third souterasi, where it rises and again
descends, as at the last station. Here a reservoir receives
it and distributes it in different directions by orifices of
which the discharge is known.” Again he savs, “ it re¬
quires but little attention to perceive that this system of
conducting tubes is nothing but a series of syphons open
at their upper part, and communicating with each other.
I he expense of a conduit by souterasi is estimated at
only one fifth of that of an aqueduct with arcades.” We
really cannot perceive any advantage in these pyramids,
further than as they serve the purpose of discharging the
air which collects in the pipes. For if the water is to be
conveyed in pipes across the valley, what other purpose
can these columns possibly serve ? I hey are in themselves
an evident obstruction, and the water would flow more
freely without any interruption of the kind. In regard to
the leaden pipes, again, they would have required, with so
little head pressure as is stated, to be used of very extra¬
ordinary dimensions to pass the same quantity of water
as was discharged along the arched conduits. There is
something, therefore, which would require explanation in
this account of Andreossy regarding these pyramids, or
else he has misunderstood the nature of them when he
says that they supply advantageously the place of the
aqueducts or arches. A train of pipes properly laid, and
of proper dimensions, might do this; but what advantage
the pyramids possess further than to answer the purpose
of air-cocks, is not very apparent.
The other principal source from which Constantinople
is supplied, is from the high grounds six or eight miles
west of the town, from which it is conducted by conduits
and arches, in the same manner as the others. The sup¬
ply drawn from all these sources amounts, according to An¬
dreossy, to 400,000 cubic feet per day; about two thirds
of a foot to each person of a population of 600,000. The
charge of the water-works at Constantinople belongs to
a body of 300 lurks and 100 Albanese Greeks, who form
almost an hereditary profession.
Of the aqueducts which still remain as relics of Roman Aqueducts
grandeur, the most remarkable are, the aqueduct of Metz; of Metz,
the aqueduct of Nismes, or the Pont du Gard; and the Nismes>
aqueduct of Segovia in Spain. “ The aqueducts of Rome,” Seg0‘
says Montfaucon, “ were without doubt wonderful on ac- ia
count of their great length—arcades continued over the
space of 40 or 50 miles; their great number, with which
the Campagna of Rome was filled on every side: all this
surprises us. But it must be confessed that if, without
considering the total extent, we only look at any of the
parts which remain round Rome, there is nothing that
approached the aqueducts of Metz, of Nismes, or of Se¬
govia.” The aqueduct of Metz is represented in Plate
XLY. Nearly the half of it, it will be observed, has
been carried away; but there still remain a great num-