had been placed there after the reign of Hadrian. The other two altars which bear his dedication both appear to have come from the ditch of the east annexe, which cannot belong to the earliest period of occupation. The nomen Aelius of the decurion Aelius Marcus suggests that he lived not earlier than the reign of Hadrian. The few fragments of pottery associated with the altar of L. MAXIMIVS GAETVLICVS indicate that it had been thrown into the pit in which it was found during the second century.

Probably, then, all of the altars belong to the second century. At the same time the evidence they convey is insufficient to determine the garrison of the fort at any one period. On a permanent frontier, such as we have in the German Limes, the legionary troops were stationed in the rear—in the great fortresses at Windisch, at Strassburg, at Mainz, at Bonn,—while the auxiliaries held the chain of smaller posts that marked the actual line of the frontier. Such obviously was the case in Britain too during the more or less settled period which appears to have followed the advance of Lollius Urbicus. The legions lay at York and at Chester; the auxiliaries—Tungri, Baetasii, Hamii, Nervii, and others—occupied the posts on the Wall of Hadrian and the Vallum of Pius, as well as on the lines of communication. There is no doubt, however, that the legionary troops took part in the expeditions into the north and in the building of the Vallum of Pius. The Ninth, the Second (Augusta), and the Twentieth Legions, possibly also the Second (Adjutrix), accompanied, or may have accompanied, Agricola in his expedition into Caledonia. The Second (Augusta), the Sixth, and the Twentieth Legions all took part in building the Antonine Vallum, and we find the traces of legionary troops as well as of auxiliaries in more than one of the Roman forts in Scotland. From Castlecary, we have inscriptions commemorating the Second and Sixth Legions and the First Cohort of Tungrians.[1] From Birrens we have inscriptions of the Sixth Legion, the Second Cohort of Tungrians, and the First Cohort of Germans styled Nervana.[2] The evidence from the inscriptions on the Wall of Hadrian seems to prove that from time to time advanced posts were garrisoned by legionary troops, as, for example, the dedication of an altar to the god Cocidius by soldiers of the Twentieth Legion, which was found in a mile castle to the west of Birdoswald, and is now at Lanercost.[3] As a matter of fact, the presence of this legion in the north is attested by many inscriptions, not only

1 Proceedings of the Society of Antiquaries of Scotland, vol. xxxvii. pp. 75, 78.

2 Ibid. vol. xxx. p. 47 ff.

3 Bruce, The Roman Wall, p. 268.