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Skip to 0 minutes and 9 secondsArchaeologists typically uncover building plans, and while understanding these structures is very important, we can extrapolate further meaning and interpretation from buildings. Let's take, for example, the granary, or the horreum, as it's know in Latin, which is a standard feature of every fort. The structure itself tells us a lot about how the Roman army stored its food. It has stone foundations and a raised and ventilated floor. These features helped to keep grain dry and reduce rotting. But granaries can also give us some very crude calculations to determine the storage capacity of the building, and then this capacity can be related to the amount of time and people that can be fed from the stores.

Skip to 0 minutes and 43 secondsOnce we have this information from a single granary, we can extrapolate even further by looking at how many granaries are found in a fort. So in the case of the supply base at South Shields, we can establish a general idea of how many soldiers can be supplied with food and for how long. We can do this in five simple steps.

Skip to 1 minute and 3 secondsIn Step 1, we need to determine the area and the volume of the granary. First we need to calculate the floor area of the granary. Now we need to deduct the area of the central passage that runs through the middle of the granary. This then provides us with a total floor area of 98 square metres. We can then turn this area into three dimensions, or volume, by considering the height available. If we take a height of 2.5 metres, we can then calculate a total volume capacity of 245 cubic metres.

Skip to 1 minute and 39 secondsIn Step 2, we now have to consider how much space does wheat really need. Based on evidence from granary buildings themselves, we believe that wheat and other cereals were stored in sacks rather than loose in bins. So we can use a sack as a measure. And we know that 0.6443 tonnes of wheat can be stored in one cubic metre of space. Multiplying this figure by the volume calculated for the granary provides us with a figure for the total capacity of the granary, 157.85 tonnes. In Step 3, we consider how many days and for how many soldiers the granary will feed. We know from Roman texts that a soldier was expected to eat 0.8 kilogrammes of grain per day.

Skip to 2 minutes and 26 secondsSo a century of 80 men would require 64 kilogrammes of grain per day. A cohort of 480 men would require 384 kilogrammes per day. Comparing this to the total capacity of a granary, that means a granary could feed a single soldier 197,312.5 days, or a century for 2,466.4 days, or a cohort for 411 days. In Step 4, let's consider what this means for the first phase of the supply base fort at South Shields, which had 15 granaries. Remember that each granary could supply more soldiers for less time. For example, a granary could supply four cohorts for 100 days each. Or how long could it support a legion of approximately 11 cohorts worth of soldiers?

Skip to 3 minutes and 20 secondsWhat about a campaigning army, like that brought by Septimius Severus, which might consist of four legions and another 10 cohorts. So how many soldiers could the first phase supply base at South Shield support? And for how long?

Skip to 3 minutes and 38 secondsFinally, in Step 5, we have to remember that these figures above are really very crude and simple. In reality, a number of factors would reduce or increase these figures. So what aspects do we need to further consider? For example, what might mean there's less grain available? Or what might mean there's more grain? Consider these aspects.

Mathematica Militaris

Archaeologists typically uncover buildings plans, and while understanding these structures is very important, we can extrapolate further meaning and interpretation from buildings.

In this video we use the example of the granaries at the supply base in South Shields and begin to consider what the physical size of the granaries can tell us about how many soldiers can be supplied with food.

After viewing the video add your thoughts on the questions we pose:

  • How many soldiers could the first phase supply base at South Shields support and for how long?
  • In reality, a number of factors would reduce or increase these figures. What aspects do we need to further consider?

Hints:

  • Think about environment and climate
  • Would all the food be for soldiers?
  • Note that cat skeletons have been found in granaries
  • Note the size of the buttresses. What might these suggest about the height of the building and number of floors?

Once you have explored these questions, you might want to listen to or read Rob’s thoughts in the downloads section below.

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This video is from the free online course:

Hadrian's Wall: Life on the Roman Frontier

Newcastle University

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