It is to this period that the traces of the Roman roads beyond the wall must be attributed, and their remains, with those of the Roman camps beyond the Tay, enable us to trace Severus’s route. He advanced to the northern wall by the road called Watling Street, repairing the fortifications of the stations as he passed.[77] From the wall near Falkirk, a road proceeds in a direct line to Stirling, where the great pass over the Forth into the north of Scotland has always had its locality. From Stirling westward along the banks of the Forth, where now are to be seen the Flanders and Kincardine mosses, there must have extended one dense forest, the remains of which are imbedded in these mosses, and there, at some depth below the present surface, are to be found remains of Roman roads. From the west of the district of Menteith to Dunkeld must have stretched a thick wood of birch and hazel, and from Stirling the Roman road proceeds through Stratherne to the junction of the Almond with the Tay. Crossing the Tay, it leaves the camp at Grassy Walls, which had been occupied by Agricola, and proceeds in the direction of a large camp near Forfar termed Battledykes. This camp is larger than any of those which may, with every appearance of probability, be attributed to Agricola, and is capable of holding a greater body of troops than his army consisted of; while, if the view we have given of his campaigns be correct, it lay beyond the limit of his utmost advance into the country. From the great camp at Battledykes, a line of camps, evidently the construction of one hand, and connected with each other by a continuation of the Roman road, extends at intervals corresponding in distance to a day’s march of a Roman army, through the counties of Forfar, Kincardine, and Aberdeen, till they terminate at the shores of the Moray Firth.[78] Severus is said by the historians Dio and Herodian to have entered Caledonia at the head of an enormous army, and to have penetrated even to the extremity of the island, where ‘he examined the parallax and the length of the days and nights.’ It would appear from these silent witnesses of his march, that he had opened up and occupied the country between the northern wall and the Tay; that he had then concentrated his army in the great camp at Battledykes, and leaving a part of his troops there to prevent his retreat from being cut off, had penetrated through the districts extending along the east coast till he had reached the great estuary of the Moray Firth, where the ocean lay extended before him, and he might well suppose he had reached the extremity of the island.[79]