Between the mile-castles, four subsidiary buildings, generally denominated TURRETS or WATCH TOWERS, were placed. They were little more than stone sentry-boxes. It is with much difficulty that they can now be traced. Horsley, in his day, complained that ‘scarce three of them could be made out in succession.’ Would that the modern antiquary could make the same lamentation! Scarcely one along the whole line can with certainty be determined. They contained an interior space of eight or ten feet square. Horsley states the distance between them to have been three hundred and eight yards—the whole number would consequently be three hundred and twenty. Though small buildings, they were, like all the works of the Romans, built for perpetuity. Hodgson found the walls of one near Birdoswald to be nearly three feet thick. Such were the buildings provided for the lodgement and security of the cohorts, whose hard lot it was to guard this frontier barrier. A plan of Cilurnum, and the works in its vicinity, taken from Warburton’s Vallum Romanum, in Plate II., exhibits these arrangements, and shews, as he remarks, how the Wall and the Vallum, the stations, turrets, and castles, yielded mutual assistance to each other. [Sidenote: THE MILITARY WAY.] But all these arrangements were not enough; without ROADS, one important element in the strength of the Great Barrier would have been wanting. Nothing economizes military force more effectually than the possession of means for quickly concentrating all available resources upon any point that the enemy may select for attack. The advance of Roman armies, and the formation of roads, were uniformly contemporaneous. The Barrier had its MILITARY WAY. It is impossible to over-estimate the importance of this part of the works. Without it, all the rest would have been useless. It would not, perhaps, be incorrect to say that both Vallum and Wall were subsidiary to it, and that the chief use of these structures was to guard the road, and to protect and conceal from view, both on the north and south, the troops that marched along it. The modern history of the district traversed by the Wall furnishes a singular corroboration of this opinion. In the rebellion of 1715, the operations of the royalist forces were greatly impeded by the absence of a good road between Newcastle and Carlisle. In the rebellion of 1745, a similar inconvenience was experienced. Marshal Wade was at Newcastle when the Pretender appeared before the city of Carlisle. The commandant of the city immediately sent an express to inform him of his position. The general’s answer contained these words:— Newcastle, November 10th, 1745, 7 o’clock. GENTLEMEN,