Hadrian’s Wall from Tyne to Solway (p. 186) has assumed a very different historical appearance since Mommsen wrote his paragraphs on it in 1885. Then, the theory of Hodgson and Bruce held the field--that the stone wall which is still visible, and the double rampart and ditch to the south of it (called by English antiquaries the “Vallum”), were both Hadrian’s work, the wall for defence against Caledonia and the “Vallum” for defence against stray foes from the south. This view was accepted by Mommsen. But later excavation and observation have shown that the “Vallum” cannot be regarded as a military work--though it is certainly Roman and connected with the wall. Excavations have also shown that the wall itself falls into two periods. At Birdoswald (Amboglanna) there was first a wall of turf (_murus caespiticius_); later, almost but not quite on the same line, came the wall of stone and the fort of Amboglanna in its present form. Similarly at Chesters (Cilurnum) two building periods are discernible; the character of the first is obscure, but the stone wall and the fort of Cilurnum belong unquestionably to the second (_Cumberland Arch. Soc._ xiv. 187, 415, xv. 180, 347, xvi. 84; _Arch. Aeliana_, xxiii. 9). As our ancient authorities persistently mention two wall-builders, Hadrian and Severus, and as the earlier wall of turf can be assigned to no one but Hadrian, it would seem that we may assume a first fortification of the Tyne and Solway line in turf about A.D. 120, and a rebuilding in stone, on almost exactly the same _tracé_, about A.D. 208 by Severus. The “Vallum” seems to have been built in relation to one or the other--more probably the earlier--of these stone walls, and may represent a civil frontier contemporaneous with it (Mommsen, _Gesammelte Schriften_, v. 461; Pelham, _Trans. Cumberland Arch. Soc._ xiv. 175). The attempt of Dr. E. Krueger (_Bonner Jahrbücher_, cx. 1-38) to show that the “Vallum” is an earlier independent work, built by Hadrian, while the turf and stone walls are post-Hadrianic, seems to me both unproven and contradicted by recent excavations.