cut, has been decidedly below the south bank, the earth has
a narrow top and heaped-up shape, which, viewed from the
north, present all the appearance of a mound. At such
places it is easy to understand how Gordon1 took the outer
mound for a rampart. To what extent in the general case
the ditch was deepened and the counterscarp, in these cases,
heightened by the earth so heaped up, our sections do not
enable us to determine exactly,2 but it is safe to say that this
artificial heightening of the counterscarp and consequent deepen-
ing of the fosse was constant, systematic, and considerable.
The rule which, in a rough way, appears to account for the
curious irregularity of the outer mound cannot be laid down as
one mathematically demonstrable at every point along the vallum.
It is only a rough and very general rule on which no great
stress can be laid. It is that where the natural levels of the
two sides of the ditch were much the same (and particularly if
the north side had slightly the advantage), it was not expedient
to heap up the earth with a narrow surface or a sharp crown, as
that would have been to rear on the north side of the fosse a
rival to the vallum on the south side. Hence, when there was-
an original approximate equality of level on both sides of the
fosse, the outer mound there is spread out with a broad, fiattish
surface. On the other hand, where the ground across the
ditch had a large fall northward and lay clear below the
berm, the outer mound has the heaped-up shape, a somewhat
narrower base, and a higher and narrower crown, which some-
times is only a rounded angle.
There are some places on the outer mound where the appear-
ances—as, for example, not far from sections at Croy (Nos. 3, 5,
and 6) and at Bonnyside between sections 1 and 2—are rather
suggestive of the possible existence of structures there, but
on the whole we believe that most of these peculiarities are
the result of mere irregularities in the shape of the ground.
If they had been outworks of the vallum it would have been
natural to expect that they would have been guarded by a fosse,
1 See p. 37, supra.
- Between 2 feet and 4 feet may be taken as an approximate statement of the
additional height thus given at the edge of the counterscarp.