Blatobulgium
The site, mentioned in the Antonine Itinerary, is ca. 2.4 km E of Ecclefechan, at the junction of the Mein Water and the Middlebie Burn. The visible fort, with rampart and ditches well preserved, is of Antonine or mid 2d c. date.
The S part of the area had earlier been occupied by a late 1st c. enclosure, constructed as a result of Agricola's campaigns in Scotland. It was probably ca. 70 m square, defended by a turf rampart and ditch. This enclosure was directly succeeded by a fort of Hadrianic date (stratified pottery). It had a turf rampart 6.7 m wide enclosing an internal area of ca. 1.34 ha, one ditch on the N side, and at least one ditch on the E and W sides. The S side has been eroded by the Mein Water. Barrack blocks were of timber, but the central block of buildings may have been of stone. The Hadrianic fort faced S, and was apparently an outpost fort to Hadrian's Wall. The inner of two triple-ditched enclosures visible on air photographs in the field W of the site was probably an annex.
The Hadrianic fort was leveled to make way for a new, longer fort, presumably with a larger garrison or a larger mounted contingent. The new fort (proved to be Antonine by stratified coins and pottery) had its E and W ramparts, and probably its S rampart, on approximately the same lines as the Hadrianic fort, but its N rampart lay over 18 m N of the earlier one.
The longer, Antonine fort measured ca. 153 m N-S and ca. 106 m E-W internally, an area of 1.6 ha. Its rampart (the present visible one) was of turf, set on a stone base 5.4 m wide, with six ditches on the N side, and one ditch at least on the E and W. In the interior a new central block of stone buildings was erected over the leveled debris of Hadrianic structures, and N and S of the central block were long narrow buildings also of stone, either barracks or stables. Inscriptions show that the garrison was the Cohors I Nervana of Germans, 1000 strong, with a mounted contingent.
The Antonine fort, as first built, suffered serious damage, resulting in a layer of debris and burned material. By A.D. 158, it had a new garrison, the Cohors II of Tungrians, also 1000 strong, with a. mounted contingent. No alteration was made in the dimensions, but extensive repairs and rebuilding were needed in the interior. The outer of the two triple-ditched enclosures in the field W of the fort was probably an annex. Birrens, for a time at least, formed part of the system supporting the Antonine Wall between Forth and Clyde.
None of the pottery found in the 1962-69 excavations was later than the 2d c. A.D., but later Roman occupation in the vicinity of the visible fort is proved by stray finds of early 3d c. pottery from the bed of the Mein Water. These may have come from one of the structures discovered by aerial photography N and S of the fort.
BIBLIOGRAPHYProc. Soc. Antiquaries of Scotland 30 (1896) 81-199; 72 (1938) 275-347; A. Robertson, Birrens (Blatobulgium) (1974).
A. S. ROBERTSON