which varies from 3-1/4 to about 5 ft.
wide. Of the pillars which carried the conduit-pipe to Antioch in
Pisidia, nineteen are still standing. Each arch consists of eleven
keystones; no cement was used. The conduit, which was high-pressure,
ends in a distributing tower and reservoir. (J. M. M.)

II. _Medieval._--The aqueduct near Spoleto, which now serves also as a
bridge, is deserving of notice as an early instance of the use of the
pointed arch, belonging as it does to the 7th or 8th century. It has
ten arches, remarkable for the elegance of their design and the airy
lightness of their proportions, each over 66 ft. in span, and about 300
ft. in height.

Constantinople.

The aqueduct of Pyrgos, near Constantinople, is a remarkable example of
works of this class carried out in the later times of the Roman empire,
and consisted of two branches. From this circumstance it was called Egri
Kemer ("the Crooked Aqueduct"), to distinguish it from the Long
Aqueduct, situated near the source of the waters. One of the branches
extends 670 ft. in length, and is 106 ft. in height at the deepest part.
It is composed of three tiers of arches, those in each row increasing in
width from the bottom to the top--an arrangement very properly
introduced with the view of saving materials without diminishing the
strength of the work. The two upper rows consisted of arches of
semicircles, the lower of Gothic arches; and this circumstance leads to
the belief that the date of the structure is about the 10th century. The
breadth of the building at the base was 21 ft., and it diminished with a
regular batter on each side to the top, where it was only 11 ft. The
base also was protected by strong buttresses or counterforts, erected
against each of the pillars. The other branch of the aqueduct was 300
ft. long, and consisted of twelve semicircular arches. This aqueduct
serves to convey to Constantinople the waters of the valley of Belgrad,
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 m.
from the city, and between 3 and 4 m. west of the village of Belgrad, 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