Again, in most of the small permanent forts that have been excavated, the plans of the various structures which covered the interior are obviously incomplete. Any tents which may have housed the garrison can have left no indication of their position. Buildings of wood and even of stone have often disappeared completely, so that in many cases, especially in the forts of the German Limes, we find little remaining but the central Principia. And yet, as fort after fort is excavated, the gaps in our knowledge are gradually being filled in, so that we can lay down the plans of the various buildings with some approach to completeness, and can recognise certain definite types, each designed for some special purpose.

In Britain, at least, these types are fairly constant. We find them more or less perfectly reproduced at Birrens, at Camelon, at Ardoch, and at Lyne, just as at Housesteads and at Gellygaer. The Principia occupies a central position opening upon the Via Principalis. On either side of it, in the spaces corresponding to the Latera Praetorii of the Hyginian camp, we have a number of buildings, evidently of an administrative character, grouped together. In the space lying in front of the Principia—corresponding to the Hyginian Praetentura—we have barracks for the soldiery. The space behind it—corresponding to the Retentura—is similarly occupied. The same general plan was employed in the larger area of the Newstead fort.

Streets and Drains

Of the streets which divided the fort, the Via Principalis, running between the gates on the north and on the south, was the broadest. In width it seems to have occupied a space of from forty-five to sixty feet, hut no kerbs or definite margins were discovered. The parallel street to the west was less wide. It measured about forty feet, and this was also the width of the street running from the Principia to the east gate. A carefully devised system of drainage carried off the surface water from the low-lying portions of the fort. A stone-built drain ran from the south-east corner of Block XIII westwards. Crossing the Via Quintana, it. followed the line of the inner ditch of the early fort, into which it had been carefully built, to a depth of eight feet. It was one and a half feet wide and was covered with large slabs of stone. Into this drain was carried the surface water from the streets running north and south between the barrack blocks of the Retentura. A second main drain ran from the east side of the Via Principalis, and, crossing the street, passed along the north side of Block XIII. Into this drain was led the