The best refutation, however, of this theory, is the fact, that in other places the Romans, about the same period, raised similar barriers. At two of these we shall glance, before beginning a detailed inspection of the Barrier of the Lower Isthmus. The comparison will probably afford valuable instruction. [Sidenote: THE GERMAN BARRIER.] The DEVIL’S WALL, in Germany, bears many marks of resemblance to the English Wall. It seems[50] to consist of the _Pfahl_, a mound of stakes, or vallum, ascribed to Hadrian, and a stone wall which is said to have been executed by some of his successors. The works extended westwards from Regensburg [Ratisbon] on the Danube, towards the sources of that river, a distance of nearly two hundred miles. They formed the boundary of the Roman empire in those parts where the Danube was not broad and deep enough to be of itself a sufficient protection. A deep trench ran along the Wall on its northern side, and along its southern face roads and camps were formed. At regular intervals of one mile, towers of observation were placed of the same size, though, being circular, not of the same form as the mile-castles on the English Wall. It is not possible, from the present remains, to determine with certainty the height or breadth of the Wall. ‘I found it in many places,’ says Professor Buchner, ‘from four to six, in others from ten to twelve, feet broad. We may therefore perhaps conclude, that its medium breadth was from six to seven feet, and that its height, as corresponding to this breadth, may have been from eighteen to twenty-four feet.’ The works have the same tendency to advance in a straight line as those of our own Barrier. ‘No mountain is so high, no abyss so steep, no wood so thick, no morass so profound, through which it does not penetrate.’ ‘The whole line of the fortification has been laid down and executed according to a well-digested plan.’ [Sidenote: THE ANTONINE WALL.] GRAHAM’S DIKE, so denominated probably from the Celtic words _grym_, strength, and _diog_, a ditch, is a barrier which fortified the Upper Isthmus of Britain. It extended from Borrowstoness, on the Firth of Forth, to West Kilpatrick, on the river Clyde, a distance of about twenty-seven English miles. It was constructed by Lollius Urbicus in the reign of Antoninus Pius, the adopted son of Hadrian. The following succinct account of this important design is taken from the ‘Caledonia Romana,’ a work of great ability, by the late lamented Mr. Robert Stuart, of Glasgow:—