An Agricolan Praesidium on the Forth-Clyde Isthmus (Mollins, Strathclyde)

ACITUS tells us1 that in A.D 81, during Agricola's fourth campaign, the Roman army paused in its northernward advance into what is now Scotland and sought to consolidate the conquest of those areas which had already been overrun. To ensure that such work went on undisturbed by incursions from Caledonia, a number of garrisons were deployed along the narrow neck of land between the estuaries of the Rivers Forth and Clyde a line of natural strength later favoured by the builders of the Antonine Wall. The exact position of these Agricolan praesidia has long been a matter for debate, but until quite recently most historians would have agreed with Sir George Macdonald in assuming that they underlay the forts on the second-century frontier. In Macdonald's words,2 the Flavian garrisons 'really determined the course of the Antonine Limes, inasmuch as they fixed the points at which the Antonine castella were destined to stand', and considerable effort, not to say ingenuity, has been employed to prove or disprove that not unreasonable assumption. However, the unexpected discovery of a new fort in the central sector of the Isthmus has provided a suitable occasion for the re-assessment of the evidence relating to the Agricolan 'frontier'. In July 1977 an aerial survey team of the Royal Commission on the Ancient and Historical Monuments of Scotland, returning to Edinburgh from a sortie over Argyll, discovered and recorded crop-marks indicating the presence of a small Roman fort at Mollins, Strathkelvin District, Strathclyde (PL. IA, FIG. Ib-c). The site lies a little more than 2-5 Roman miles south of Bar Hill on the Antonine Wall, on the south bank of the Luggie Water at the west end of a low ridge, and about 150 m north-east of Mollins farmhouse (NS 713718). The fort measures