ROMAN FORTIFICATION. 139 



been ruined for defensive purposes by the Danes, but considerable 

 portions of it, and we may assume the whole of the foundations, 

 remained up to comparatively recent times. On Speed's map, 

 which was published in 1610, the foundations of the whole of the 

 walls are figured, and I understand Dr. Stukeley to say that in his 

 time the foundation of the wall could be traced. Since then most 

 of the wall has been destroyed. In 1764 85 feet of it was 

 pulled down and only 77 feet left standing. In the summer of 

 1802 another portion of the old wall was removed, and now little 

 more than a fragment remains. 



As to the manner in which walls of fortified towns were built we 

 have the clearest evidence. The principal ditch was first marked, 

 then dug out. This ditch was wide and deep, the soil dug out of 

 it was used to form a rampart on the town side ; the ditch was 

 deepened close to the rampart to receive the foundation of the wall. 

 On the other side of the rampart a second wall was built to 

 keep the rampart in position and to back it up, and the soil 

 between them was well rammed down. Vegetius explains the 

 construction simply : "A rampart, to have sufficient strength and 

 solidity, should be thus constructed. Two parallel walls are built 

 at the distance of 20 feet from each other, and the earth taken out 

 of the ditches thrown into the intermediate space and well rammed 

 down. The inner wall should be lower than the outer to allow an 

 easy and gradual ascent from the level of the city to the top of the 

 rampart. A ram cannot destroy a wall thus supported by earth, 

 and in case the stonework should by accident be demolished the 

 mass of earth within would resist its violence effectually." 

 Vitruvius' plan was similar but more elaborate. He advises that 

 the main wall shall be tied from front to rear with olive wood 

 beams, and the two walls united by cross walls "disposed as 

 the teeth of a comb or saw usually are, for when this has 

 been done the great weight of earth (between them) will be 

 distributed into small parts, and so will not be able by the pressure 

 of its united weight to push out the substructure of the walls in any 

 degree " (Lib. I. cap. 5). These zigzag cross walls tying the main 



