THE DEVELOPMENT OF THE WALL S urveys by the writer in Britain and Germany 1 have recently revealed a consistent pattern of Roman frontier communications in which each system's minor installations were sited so as to be able to see, and thus to signal to, their nearest fort, whilst the forts themselves could be linked to form a unified chain. But, until recently, the Antonine Wall appeared so different that it seemed unlikely that it operated in the same way. Comparing the two British Walls, both share the basic framework of a rampart and ditch and the change from stone to turf construction, on the northern system, is mere detail, but differences in the garrison installations did seem to have been of operational importance. For example, the inter-fort spacings of the Antonine Wall were much shorter, varying from 1.56 to 3 Roman miles, as against 6 to 9 on Hadrian's Wall-producing 17 known (including Carriden) and several suspected forts in c. 40/2 Roman miles, 2 as opposed to 16 in 80 Roman miles on the southern Wall. Moreover, many Antonine Wall forts were too small to have held a full auxiliary unit and there seemed to be no sign of a fortlet and turret system. Today, however, there is general, if qualified, acceptance of Gillam's hypothesis 3 that the Wall was initially designed as a copy of the secondary, Wall fort, phase of Hadrian's Wall. The theory suggests that the system was originally held by just the six largest forts, a group ranging from c. 3.5 to 6.5 acres and taking in Carriden, Mumrills, Castlecary, Balmuildy, Old Kilpatrick, and one other. The remaining forts would belong to a secondary phase; some may have been planned by the time the Wall was under construction. Gillam extrapolated from the small number of minor sites then known to suggest that a milefortlet, and even a turret, system might one day come to light. The discovery of additional fortlets and the fact that the newly discovered fort at Inveravon 1