ROMAN URBAN TOPOGRAPHY in Britain and the western Empire

Crummy: Colchester: the mechanics of laying out a town
Fig 54 The street system of Silchester (taken from Boon 1974), with dimensions in pedes monetales (Actual measurements in
italics, theoretical dimensions in upright bold)
eastern grid there was a hiatus long enough for construction
of the theatre to begin.
Taken together, the various strands of evidence indicate
that the eastern grid may not have been laid out until the
mid 50s. The process could have been quite complex, with
various stretches of the defences being levelled independently
over a period of years.
The layout of the town’s street system in its original
form is accurately known in places, so that theoretically it
ought to be possible by careful measurement to determine
the strategy of the planners. It appears that in at least some
towns and fortresses planners adopted a common
approach: the layouts were formulated in terms of round
figures and the planning of buildings was secondary to the
street system. In other words, the buildings were made to
fit the street plan rather than vice versa.
At Silchester, careful measurement of Boon’s large plan
of the town (Boon 1974) reveals that its layout was based
on a series of rectangles sharing the dimensions 250, 275,
and 400 standard Roman feet (pedes monetales) (Fig 54;
Crummy 1982a, 130-2). The streets seem to have been 25
feet wide. To show this, the width of each row of insulae
80
was measured at either end to gauge the degree of accuracy
of the layout. From these measurements, the scheme
conceived by the planner emerged. To check its consistency,
measurements were taken across several rows of
insulae and these were found to compare well with the
theoretical dimensions. Thus, east-west the actual
measurements of 1297 and 1283 compare well with the
theoretical dimension of 1300, whilst north-south the
measurements of 1794 and 1795 are very close to the
theoretical 1800 feet. The measurements were made in
metres (since the plan is metric) and converted into
Roman feet by taking one pes monetalis to equal 0.295m.
The fact that the measurements in Figs 54 and 55 are all to
the nearest Roman foot does not reflect their degree of
accuracy. Various factors affect the quality of the
measurements and combine to make it very difficult to
estimate the actual level of precision. No doubt it would
have been more realistic to have rounded off the figures to
the nearest multiple of five, but it seems simplest to leave
the measurements in their raw form.
Inspection of the street system of Caistor-by-Norwich
reveals that it was formulated on the basis of a series of