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 ROMANO-BRITISH DERBYSHIRE and some securing the roads which led to them or which traversed the restless hill country in the north or in Wales. It must be observed that in this system it was not only the forts that were permanent, but also their garrisons. Our English regiments relieve one another periodically at brief intervals in India or South Africa. The Roman legions or cohorts were not thus moved about. The same Roman corps stayed in the same province and in the same garrison for scores of years, and possibly for centuries. Thus the three British legions mentioned in the last paragraph remained in the same places for over two centuries each, and the cohorts and ' alas,' which are named as garrisoning the Roman wall between Tyne and Solway near the end of the Roman dominion, are largely the same that we find there in the second century. The whole of this arrangement was based on the presumption that the principal task of the troops was to act as garrisons. For this purpose it served well enough. But it allowed no provision for a large field force. When such was required it was collected by reducing the strength of individual garrisons or by withdrawing troops from quieter provinces. This, however, was a temporary makeshift. The crisis over, the detach- ments went back to their forts and fortresses and resumed their permanent duties. Here we touch the characteristic point of the system. The Roman army in each province was a garrison army, and the essential feature was the fort or fortress in which each unit was stationed. These forts and fortresses were laid out according to one model. Their internal arrangements were not left to the genius or the whims of particular commanders, but followed a prescribed and uniform pattern. The origin of this pattern may be found in the fixed scheme used since Republican days by the Romans for the encampments of their soldiers in the field. Under the Empire this pattern may be said to consist of a square or oblong enclosure with four symmetrically-planted gates and four main streets running from the four gates towards the centre of the whole. At the centre stood the headquarters buildings, the offices, and the residence of the commanding officer. Near these came the quarters of other high officers and various storehouses, while the rest of the enclosure was filled with barracks and other buildings for the use of the common soldiers and lower officers. No provision was made for traders or for womanfolk. In this, as in many other points, the plan of the permanent fort or fortresses preserves the tradition of the encampment of the marching army, and exhibits the strictness of Roman discipline. But traders and women were none the less inevitable, and there usually grew up outside the fortress gates a ' civil settlement ' of camp followers, and not unfrequently old soldiers settled here after their discharge, preferring to remain in the familiar scenes of their active life. This general plan of fortress was used equally for the large legionary fortress and the smaller fort of an ' ala ' or cohort. But the great difference in area naturally produced differences in internal detail. A fortress intended for 5,000 men with important officers and elaborate '95