Nothing had as yet emerged to furnish an explanation of the changes in the ground plan that have just been indicated. The reason, however, became clear when in 1907, in tracing the walls of the barrack blocks in the Retentura, there came to light the foundations of the heavy wall, six feet in width, crossing the fort from north to south parallel to, and about seventy feet from the west side of; the Via Quintana, which has already been referred to as the reducing wall. It had a gateway flanked by guard chambers at the point where it crossed the main road that ran from east to west. The new wall had evidently been erected in order to reduce the size of the fort.

Figure 4

The Reduction in Size

The area cut off comprises the lowest and wettest portion, and the black, peaty matter, which lies over it, would suggest that at one time it had been flooded. In extent it measures about one-third of the whole space originally enclosed, and its abandonment would appear to indicate a definite period of occupation. With the reduction in the size of the fort the existing lines of road ceased to be in accordance with the recognised plan. The street which served as the earlier Via Principalis no longer formed the central artery of communication, and the Principia, if left facing the west,