Glasgow Archaeological Society   [Hrsg.]
The Antonine Wall report: being an account of excavations, etc., made under the direction of the Glasgow Archæological Society during 1890 - 93 — Glasgow, 1899

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THE ANTONINE WALL REPORT.

129

If we knew how many horizontal rows of sod there were in a
section of the vallum in its perfect state, it is obvious that that
number multiplied by the original thickness of the sod would
give the approximate height. But it is a hard question to
answer how many layers of sod there were in the vallum. The
largest series yet found was at Roughcastle No. 3 section,
where there were 19 layers now standing, 4 feet 8 inches high,
or an average of 3 inches to each layer. If we could assume
that the original sod wTas not less than 5 inches thick,1 and that a
few layers have by time and weathering disappeared, we might
with tolerable safety infer that (independent of any wooden battle-
ment) the wall at Roughcastle was not much over 10 feet high.
That section at Roughcastle, however, is not a portion of the
wall proper (as it is the wall of the camp), but at Croy No. 11 and
Barr Hill No. 1 we have sections of the actual vallum which in
height resemble that at Roughcastle. In these there are 19 layers
with heights of 58 and 52 inches. Making similar allowances to
those postulated at Roughcastle, the heights of the Croy and Barr
Hill portions might be reckoned also as not exceeding 10 feet. The
evidence of the sod layers, therefore, so far as it goes, would not
warrant a belief that the wall was ever much higher than 10 feet.

One point of great importance in this problem appears to have
escaped the notice of all previous writers. The sides of a wall
of earth, whether of sods or not, must have had a decided
" batter "—that is, in order to preserve stability, it must have been
necessary to narrow the breadth as the structure rose, so that
the top of the wall would be considerably narrower than the
base. It is very interesting to find in the work of the Roman
architect Vitruvius 2 a canon for the breadth of a rampart. It is
true that he refers to the wall of a fortified town, but the dis-
tinction between such a wall and a frontier rampart, whether
erected primarily for defensive purposes or not, can scarcely
have been vital. " The thickness of the wall," he says, " should be

1 Half a foot was, it will be remembered, the theoretical thickness for the
Roman sod (p. 30, supra), but that standard could not be attained in average
soils in Scotland.

-Vitruvius, i., cap. 5. " Crassitudinem antem muri ita faciendam censeo, uti
armati homines, supra obviam venientes, alius alium sine impeditione praeterire
possint."

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