up ditches can have little real meaning unless they convey to us some impression of the appearance of the fort as it existed when tenanted by its Roman garrison. Unfortunately there are many blanks in the evidence, many points in regard to which we are left in doubt. It is only by comparison with the facts obtained from the excavation of similar defensive works elsewhere that we can hope to reconstruct the picture. The triple line of ditches stretching in front of the wall is easy to imagine. But there is nothing at Newstead to tell us how high the wall itself had stood. We only know that it was strongly founded and that it was seven feet seven inches thick.
In Britain, as on the Continent, the walls of other permanent forts have been levelled for so long that they give us little help in the task of reconstruction. To find the nearest parallel we must turn to the walls of towns. The Roman wall of London, recently exposed near Newgate, was eight feet six inches thick,[1] the wall of Cologne from six feet six inches to seven feet four inches. The wall round Nîmes and that round Arles[2] were just such walls as we find at Newstead; they were sufficiently thick to admit of two men passing each other on the top, and of some considerable height. Possibly the Newstead walls were crenellated. This is a feature which we find in the town wall of Pompeii.[3] There the wall was double, with a filling of earth between. The outer wall rose to a height of twenty-six to twenty-eight feet above the ground, and terminated in a breastwork six feet high Each battlement had a traverse of stonework covering the left side of the soldier as he looked from the wall, and protecting him from being enfiladed. Behind him the inner wall rose some sixteen feet higher, the object of the added elevation being to prevent missiles dropping into the town. Increased power of resistance, especially against battering-rams, was secured by heaping up against the inner wall an embankment of earth forming a rampart. Stairs at the sides of the gate towers gave access to the platform on the top.
Pompeii was of course a city, and its walls dated from a considerably earlier period than those of Newstead. There is no reason to suppose that the feature of the high inner wall was reproduced in the defences of the frontier forts. But dressed copestones for battlements of the same type as those of Pompeii have been found in the ditches of the forts, or associated
1 Archaeologia, vol. lix. p. 126.
2 Blanchet, Les enceintes Romaines de la Gaule, p. 258.
3 Rochas d'Aiglun, Principes de la fortification antique, p. 56, plate ii.
36