But now for the proof. In 1756 ancient paving stones were still in
situ[50] above the row of arches on the Via degli Arconi, and even yet
the ascent is plain enough to the eye. The ground slopes up rather
moderately along the Via degli Arconi toward the east, and nearly below
the southeast corner of the ancient wall turned up to the west on these
arches, approaching the entrance in the middle of the south wall of the
city.[51] But these arches and the road on them do not align exactly
with the terrace on the west. Nor should they do so. The arches are
older than the present opus quadratum wall, and the road swung round and
up to align with the road below and the old wall or escarpment of the
city above. Then when the whole town, its gates, its walls, and its
temple, were enlarged and repaired by Sulla, the upper wall was
perfectly aligned, a lower wall built on the west leaving a terrace for
a road, and the arches were left to uphold the road on the east.
Although the arches were not exactly in line, the road could well have
been so, for the terrace here was wider and ran back to the upper
wall.[52] The evidence is also positive enough that there was an ascent
to the terrace on the west, the one below the Barberini gardens, which
corresponds to the ascent on the arches. This terrace now is level, and
at its west end is some twenty feet above the garden below. But the wall
shows very plainly that it had sloped off toward the west, and the slope
is most clearly to be seen, where a very obtuse angle of newer and
different tufa has been laid to build up the wall to a level.[53] It is
to be noticed too that this terrace is the same height as the top of the
ascent above the arches. We have then actual proofs for roads leading up
from east and west toward the center of the wall on the south side of
the city, and every reason that an entrance here was practicable,
credible, and necessary.

But there is one thing more necessary to make probabilities tally