city with water, standing as it did on the side
of a hill at the junction of two great rivers (now Rhone and Saone), it
was necessary to search for a source at a sufficient height, and this
Plaucus found in the hills of Mont d'Or, near Lyons, where a plentiful
supply of water was found at a sufficient height, viz., that of nearly
2,000 ft. above the sea. From this point an aqueduct, sometimes called
from its source the aqueduct of Mont d'Or, and sometimes the aqueduct of
Ecully, from the name of a large plain which it crossed, was constructed,
or rather two subterranean aqueducts were made and joined together into
one, which crossed the plain of Ecully, in a straight line still
underground; but the ground around Lyons was not like the Campagna, near
Rome, and it was necessary to cross the broad and deep valley now called
La Grange, Blanche. This, however, did not daunt the Roman engineers;
making the aqueduct end in a reservoir on one side of the valley, they
carried the water down into the valley, probably by means of lead pipes,
in the manner which will be described more at length further on, across
the stream at the bottom of the valley by means of an aqueduct bridge 650
ft. long, 75 ft. high, and 281/2 ft. broad, and up the other side into
another reservoir, from which the aqueduct was continued along the top of
a long series of arches to the reservoir in the city, after a course of
about ten miles.

In the time of Augustus, however, it was found that the water brought by
this aqueduct was not sufficient, especially in summer; and as there was
a large Roman camp which also required to be supplied with water,
situated at a short distance from the city, it was determined to
construct a second aqueduct. For this purpose the springs at the head of
a small river, called now the Brevenne, were tapped, and conveyed by
means of an underground aqueduct (known as the aqueduct of the Brevenne)
which wound round the heads of the valleys, and after a course of about
thirty miles is believed by some to have arrived at the city, but by
others to have stopped at the Roman camp, and to have been constructed
exclusively for its supply.

I have here a diagram, after Flacheron, showing a section of this
aqueduct, and this will give a very good general idea of the section of a
Roman aqueduct where constructed underground. It will be seen that the
specus or channel is 60 centimeters (or nearly 2 ft.) wide, and 1m. 57c.
(or a little over