Transactions. 49 



minute inspection of this mound, with regard to its omission and 

 recurrence, and to give what seems to be a most reasonable 

 explanation. Owing to the vallum very often running through a 

 hilly country, it is usually less or more on the slope. Mr Neilson 

 observed that, when the slope was to the south, the marginal 

 mound was always there ; but when the slope was to the north it 

 was usually absent. The object of the mound, he therefore con- 

 jectured, was to elevate the southern lip of the fosse wherever it 

 was depressed by the slope of the ground to a lower level than 

 the northern margin, so that defenders standing on the south 

 side of the ditch would always be as high, or a little higher, than 

 those who were were standing on the north side. When this 

 advantage was already given by the slope of the ground there is 

 no marginal mound. The north agger rises very sharp from the 

 fosse, unlike the south agger, and leaves no space between on 

 which armed men could deploy, or even maintain a sure footing. 

 Between the north agger and the stone wall, where the vallum 

 and murus follow the same route, there is always, as has been 

 said, a space wide enough for troops to march along. 



Now, is it reasonably possible, looking' to these characteristics 

 of the work, to suppose that it could ever have been designed as 

 a defence against foes approaching from the south ? In that case, 

 what would have been the use of the south agg'er or the marginal 

 mound on the southern lip of the fosse ? These would have 

 assisted the assailants instead of arresting them. The defenders 

 must be supposed to be on the north side of the fosse, and there- 

 fore not at striking distance with the enemy until they were 

 attempting to cross the fosse. There would be no hindrance, 

 therefore, to the latter scaling the south agger, and finding space 

 between it and the fosse to close their ranks, whilst the marginal 

 mound would give them just that advantage in fighting which in 

 those times was always sought for in a position slightly more 

 elevated than that occupied by the foe. No reasoning that I 

 have seen or heard has done anything towards getting rid of the 

 absurdity of supposing the Komans to erect defensive works 

 against an enemy which seem to have been designed rather to 

 give him all the advantage. There is good reason, let me remark, 

 for supposing that these aggers and fosses were not relied upon 

 in their mere naked condition for defending a position. They 

 were probably studded with sharp stakes, forming a palisading 



