We now consider what conclusions, if any, may be drawn from
the mass of details in the foregoing' descriptions. In these
sections the same features present themselves again and again,
and the phenomena thus persistently repeated have suggested
many arguments and inferences, some of which we provisionally
accept, whilst in regard to others not less important we hold our
judgment in suspense. Among the subjects of detail considered
the following are of outstanding interest and moment, viz.:—
(1) The substance of the vallum; (2) its foundation; (3) its shape
and size; (4) the meaning of the berm; (5) the character of the
fosse ; (6) the nature of the outer mound ; (7) the method of the
defence of the rampart; (8) the purpose of the periodic expansions
on the southern face of the vallum; (9) the military way.
1. The Substance of the Vallum.
In view of the wealth of ancient Roman literature, historical
and technical, it is perhaps not too much to expect from classical
sources enlightenment concerning the precise methods of structure
employed in the making of these frontier walls. In the case
of the murus across North England, although no Roman
historian has recorded how it was made, it has been found
possible from the general terms of writers on architectural
matters to determine with some approach to certainty the
particular structural category to which it falls to be assigned.