The unit of Roman land-surveying, the 'iugerum', was a rectangular space of 120 by 240 Roman feet--in English feet a tiny trifle less--and it seems to follow that 'insulae' were often laid out with definite reference to the 'iugerum'.

The divisions may not have always been mathematically correct; our available plans are seldom good enough to let us judge of that,[62] and we do not know whether we ought to count the surface of the streets with the measurement of the 'insulae'.

But the general practice seems clear, and it extended even to Britain (p.

129), and though blocks forming exactly a 'iugerum' or a half 'iugerum' are rare, the Italian land-measure certainly affected the civilization of the provincial towns.
[62] Silchester and Timgad are the only two sites which have been planned well enough to provide accurate measurements.

The large modern town-plans (e.g.of Turin, p.