GLASGOW ARCHAEOLOGICAL SOCIETY.
for the interval between the vallum and the ditch in spite of its
abnormal character at this part) expands considerably, the fosse
leaving the vallum at a greater distance from it than anywhere
else on the whole line of the wall. Midway between the point
46 yards west of Croy Houses, where this separation commences,
and the point opposite this section, the berm space is 67 feet;
at the section it is 112 feet; at 24 feet further west, it attains its
maximum of 116 feet, contracting as measured at successive
intervals of about 20 yards westward to 100, 95, 70, and 54 feet
—the last measurement being taken down the line of a stone
dyke (one of three) 152 feet east of section 8.
The fosse here is very narrow. Such is its character wherever
it passes along the foot, or along the lower slope, of a hill while
the vallum keeps the summit. It does seem a little remarkable
that the ditch should have been cut here at all, when the vallum
was so well defended by a steep, almost precipitous, hillside ; but
it is certain that here, at any rate, the apparent natural revetment
of rock is, in reality, not natural in the main, but is to a large
extent, if not entirely, the work of the Komans in making the fosse.
Where, however, nature had already done so much of the work
of defence, and where the scarp of the fosse was a rocky steep, there
was no need for a ditch of the dimensions requisite on level
ground ; and accordingly its width, taken horizontally at various
points round the hill on which section No. 7 stands, is from
14 to 16 feet up to 18 and 20 feet. Its depth it is not easy to
estimate; for, while the scarp is a rocky precipice of varying
elevation, the counterscarp is very greatly lower, being a mere
lip of the ditch and relatively insignificant. Measured from
the level of the top of the counterscarp, it never reaches much
over 5 feet in depth. On the other hand, if measured from
the top of the rocky scarp the depth would be fully 25 feet in the
vicinity of section No. 7, and from 20 to 15 and 13 feet further
west, where the ditch is gradually attaining a higher level.
Thus measured, the average depth in this vicinity is about
15 feet. But the marked difference in level between the tops
of the scarp and the counterscarp—the former standing com-
pletely over the latter, as it were—makes it difficult to find a
departure point for satisfactory depth measurements.