times as
spacious; they were twice or nearly twice as large as mediaeval
Oxford, no mean city in thirteenth-century England. Most of them,
doubtless, grew beyond their first limits; a few spread as far as a
square mile, twice the extent of mediaeval London. Similarly the
'insulae' varied from town to town. In one, Timgad, they were only 70
to 80 ft. square. Often they measured 75 to 80 yds. square, rather
more than an acre, as at Florence, Turin, Pavia, Piacenza.[61]
Occasionally they were larger, but they seldom exceeded three acres,
and their average fell below the prevalent practice of modern
chess-board planning.

[61] For Florence and Turin see below; for Piacenza, the plans on
the scale of 1:1000 and 1:5000 in L. Buroni's _Acque potabili di
Piacenza_ (1895).

In most towns, though not in all, the dimensions of the 'insulae' show
a common element. In length or in breadth or in both, they usually
approximate to 120 ft. or some multiple of that. The figure is
significant. 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. 86) are useful, but
inadequate to our purpose; for one thing, they often exaggerate
the width of the streets. One really needs actual measurements
made on the spot.

In this system perhaps the most peculiar feature is the intermixture
of square and oblong 'insulae'. It is not merely the variation which
can be traced in Priene (fig. 5), where some blocks are rather more
square or oblong than others, but where all approach the same norm.
The Roman towns which we are now considering show two varieties of
house-blocks. Sometimes the bloc