If the parallelism of the lines of the Vallum be fatal to the theory, that one of the mounds is the work of Agricola, and the others the work of Hadrian, a similar mode of reasoning leads to the conclusion, that the Vallum and the Wall cannot be independent structures. If Severus, finding that the earth-works of Hadrian had fallen into decay, or were no longer sufficient to wall out the Caledonians, had determined to erect a more formidable Barrier, would he not have mapped out its track without any reference to the former ruinous and inefficient erection? Had he done so, we should find the lines taking independent courses—sometimes contiguous, occasionally crossing each other; sometimes widely separated, seldom pursuing for any distance a parallel course, but the Wall, as the latest built, uniformly seizing the strongest points, whether previously occupied by the Vallum or not. This, however, is not the case; the Wall and Vallum, in crossing the island, pursue precisely the same track from sea to sea; for the most part they are in close companionship, and in no instance does the Wall cut in upon the trenches of the Vallum. At the first view of the subject, therefore, we should be disposed to question the accuracy of the opinion which gives to these works distinct dates, and ascribes the Vallum to Hadrian, and the stone Wall to Severus. Before further prosecuting this inquiry, it will be well to lay before the reader all the statements of the ancient historians upon the matter in question; he will by this means see the necessity of appealing to the structures themselves for a satisfactory decision of the question. [Sidenote: TESTIMONY OF HISTORIANS.] Herodian was contemporary with Severus, and professes to have been an eye-witness of all that he relates. He gives a detailed account of the emperor’s proceedings in Britain, but does not once mention the Wall. Dion Cassius was also contemporary with Severus. As before observed, that part of the original work which treats of Britain is lost; we have, however, Xiphiline’s abridgment of it. The only reference which he makes to the Wall, comports with its existence previous to the arrival of Severus in Britain, Speaking of that emperor’s expedition against the Caledonians, he says— Nor did he ever return from this expedition, but died three years after he first set out from Rome. He got a prodigious mass of riches in Britain. The two most considerable bodies of people in that island, and to which almost all the rest relate, are the Caledonians and the Meatæ. _The latter dwell near the Barrier Wall_ (οιχουσι δε οἱ μεν Μαιαται προς αυτῳ τῳ διατειχισματι, ὁ την νῆσον διχῆ τεμνει) _which divides the island into two parts_. Spartian, writing about A.D. 280, is the first person who gives us any direct information about the erection of a Wall; and it is on his testimony chiefly that the credit of the work has been given to Severus. Speaking of Hadrian, he says—