144 ROMAN FORTIFICATION. 



be poured down to extinguish the fire when occasion requires." 

 This accounts for the openings over the gates of Pompeii, which 

 appear to have puzzled some antiquaries. 



We have now the fortification complete so far as this ; an inner 

 wall 12ft. thick, a rampart 15 to 25ft. wide, with an outer wall 

 retaining it, the whole about 40ft. in thickness (1),* a deep ditch 

 on the outside of that again, possibly towers in the walls some 

 eighty yards apart. 



This seems formidable enough, but the fortifications of the town 

 were much stronger than this indicates. Vitruvius says special care 

 ought to be taken that " there may not be an easy approach to 

 attack the wall, but that the wall should be surrounded by steep 

 places, and so contrived that the road up to the gates may not be 

 direct but inclined to the left, &c." At Dorchester the position 

 was strengthened in this way by throwing up two lines of ramparts 

 outside the walls. "When I was a boy the ridges of these two lines 

 were very apparent, and one at least is clearly seen on the south 

 side, and one, if not both, may still be traced on the west. As the 

 ditches were cut in the solid chalk, it will be possible by cutting a 

 trench across them to find out exactly what were their original forms, 

 their depth, and width. 



I have not discussed the question whether Dorchester was a 

 stationary fortified camp (a castra stativa), because as a fortified 

 garrison town it was that, and something more ; if it be contended 

 that Dorchester was a castra stativa for troops only, there will be 

 the difficulty of its size. I cannot find an instance of such a camp 

 being constructed five times as large as was required. Even the 

 enormous camp of Gamzigrad, in Servia, which is remarkable as 

 being one of the largest known, is not so large. Poundbury, as 

 regards size, is much more like what we should expect the 



* (1) This seems unnecessarily strong, but it must be remembered that 

 battering rams, and other engines of enormous size and power were used 

 jn warfare at that time. Vitruvius speaks of a balista which threw a 

 stone 3601bs. in weight, and of a tortoise constructed by Agetor the 

 Byzantine, for filling ditches and undermining walls, which was 60ft. 

 long and 18ft. broad. 



