The fosse of the Vallum is rather less than that of the Wall. Making a deduction of one-third on this account, and supposing that the distance which the Vallum falls short of the Wall at each extremity, makes amends for the increased labour of cutting through the rocky ground, we have 3,723,382 cubic yards to be removed, involving 465,422 days of forced labour. The whole could now be done for the sum of 23,271_l._ No account is taken of the labour expended in raising the earthen ramparts, or the cost of their construction, for the reason, that the removal of the earth from the fosse implied its being deposited somewhere; no place would be more convenient for this purpose than the mounds of the rampart.
[Sidenote: TIME REQUIRED FOR ITS CONSTRUCTION.]
Adding together these results, we find that the cost of the Wall and its north fosse would be 1,056,175_l._, and that the cost of the Vallum, added to this would form a total of 1,079,446_l._ The number of days’ labour involved in the Wall would be 2,400,249, and, adding to this, that of the Vallum, we have for the whole 2,865,671 days’ labour.
The largest number of men that we can conceive to be brought to bear at once upon the Wall, including such of the Roman troops as could be spared from military operations, is ten thousand. This body, at the rate already supposed, would, by continuous labour, execute the Wall and its ditch in 240 days, and, taking the Vallum also into account, in 286 days. In the exposed district over which the Wall runs, it is not probable that the weather would allow of the work being pursued during more than two hundred days in the year. If, in addition to this, we make deductions for the chances of war, two years may be stated as the shortest time in which the whole of the works could be executed.
A recent writer, who, in a work denominated ‘A History of the Picts or Romano-British Wall,’ adopts the notion of Gildas, that the stone wall was built, not by Hadrian or Severus, but by the trembling Britons on their abandonment by the Romans, supports his opinion by denominating the work an un-Roman-like defence, and argues that men who were unaccustomed to fear, would not seek the assistance of a wall and a ditch. However regardless of life the Romans may, in the abstract, have been, they knew how to economize their resources. In the battle of the Grampians, Agricola withheld his legionary soldiers, and made use only of his auxiliary troops. He could better afford to expend the one than the other. As well might a warrior despise the protection of a helmet or a shield, as refuse the defence of a stone wall.