GRANARIES AND GARRISONS IN ROMAN FORTS

Summary.   A statistical investigation into the relationship between granary floor area and garrison in Roman forts suggested that for a year's corn an auxiliary infantry cohort was typically allotted 2,500 sq. feet of granary area, or 5 sq. feet each for 500 men. Cavalry fort granaries were insufficient for a year's corn but each cavalryman probably had 7.5 sq. feet of granary area which gave 3,600 sq. feet for 480 men. Information from Polybius suggested that legionary and auxiliary infantrymen had 16 cu. feet of corn per year, an auxiliary cavalryman 152 cu. feet and the legionary cavalryman 216 cu. feet. This paradigm facilitated the issue of corn by the modius and the granary model allowed ten modii per sq. foot of floor area so that the input for an infantryman was 50  modii per year. This allowed for a 4 per cent loss during storage so 48  modii per man could be withdrawn. But granary areas varied and some forts appear to have been depots for others. A simple algorithm is given to list the possible options for known granaries in terms of the numbers of men and duration of supply. With two floors, the Chester granaries would hold a year's corn for a legionary establishment, while the wooden granaries at Inchtuthil would have held a year's corn for some 6,800 infantry on one floor. The Severan base at South Shields could have held a year's corn for about 11,000 infantry.