Vallum (Hadrian's Wall)

The Vallum is a huge earthwork associated with Hadrian's Wall in England. Unique on any Roman frontier, it runs practically from coast to coast to the south of the wall.

The earliest surviving mention of the earthwork is by Bede (Historia, I.12), who refers to a vallum, or earthen rampart, as distinct from the wall, or murus; the term is still used despite the fact that the essential element is a ditch, or fossa. It was for long thought that the Vallum predated the stone wall, the most elaborate phasing being presented in 1801 by William Hutton, who thought, wrongly, that the south vallum mound and the marginal mound, with a ditch between, were the work of Agricola, that the vallum ditch and north mound were added by Hadrian, and that the stone wall was the work of Severus. In fact all these elements date to Hadrian's reign, with the stone wall having been built first.

The Vallum comprises a ditch, nominally 6 metres (20 ft) wide and 3 metres (10 ft) deep, with a flat bottom, flanked by two mounds about 6 metres wide and 2 metres (7 ft) high, set back some 9 metres (30 ft) from the ditch edges. For a great deal of its length a third lower mound, the so-called marginal mound occupies the south berm (flat area between mound and ditch), right on the southern lip of the ditch. The total width of the fortification (consisting, from north to south, of mound, berm, ditch, marginal mound, berm, mound) was thus about 36 metres (100 ft).

In several places – for example at Heddon-on-the-Wall and Limestone Corner – the Vallum was cut through solid rock, sometimes for lengthy distances.

The distance of the Vallum from the Wall varies. In general there was a preference for the earthwork to run close to the rear of the Wall where topography allowed. In the central sector the Wall runs along the top of the crags of the Whin Sill, while the Vallum, laid out in long straight stretches, lies in the valley below to the south, as much as 700 metres (2,300 ft) away.

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