ported on a construction of
masonry, crossed the river by an aqueduct bridge, and ascended into
another reservoir on the other side, entering the reservoir at its upper
part just below the spring of the arches of the roof. From this reservoir
the aqueduct passed to the next on the edge of the large and deep valley
of Bonnan, being underground twice and having three bridges on its
course, the last of which, the sixteenth on the course of the aqueduct,
ends in a reservoir on the edge of the valley. Only one of the openings
by which the siphons, of which there were probably ten, started from the
reservoir is now left. The bridge across the valley below had thirty
arches, and was about 880 ft. long by 24 ft. wide.

A number of the arches still remain standing, and, the pillars of the
arches were constructed of transverse arches themselves. The work
consisted of concrete, formed with Roman cement so hard that it turns the
points of pickaxes when employed against it, with layers of tiles at
regular intervals. The surface of the concrete is covered with small
cubical blocks of stone placed so that their diagonals are horizontal and
vertical, and forming what is known as _opus reticulatum_. After crossing
the bridge the pipes were carried up the other side of the valley into a
reservoir, of which little remains, and then the aqueduct was continued
to the next valley, passing over three bridges in its course. This
valley, that of St. Irenee, is much smaller than either of the others,
but nevertheless it was deep enough to necessitate the construction of
inverted siphons, of which there were eight. Leaving the reservoir on the
other side of this valley, the aqueduct was carried on a long bridge (the
twentieth on its course) which crossed the plateau on the top of
Fourvieres and opened into a large reservoir, the remains of which are
still to be seen on the top of that hill.

From this reservoir, which was 77 ft. long and 51 ft. wide, pipes of lead
conveyed the water to the imperial palace and to the other buildings near
the top of the hill. Some of these lead pipes were found in a vineyard
near the top of Fourvieres at the beginning of the eighteenth century,
and were described by Colonia in his history of Lyons. They are made of
thick sheet lead rolled round so as to form a tube, with the edges of the
sheet turned upward, and applied to one another in such a way as to leave
a small space, which was probably filled with some kind