ROMAN URBAN TOPOGRAPHY in Britain and the western Empire

ather unpleasant finished surface (Fig 21). In the 2nd
century this gave way to the brown or grey volcanic tuff
from nearby Nuceria. Tuff was much favoured in central
Italy before the time of Caesar and Augustus because it
was readily available and had the dual advantages of being
easy to cut in the quarry and then hardening on exposure
to the air. The main snags were that it did not have the
same aesthetic appeal as the hard white stones and that
some varieties, especially the yellow tuff from the Campi
Phlegraei, north of Naples, suffered badly in due course
from the effects of weathering. Eventually, even in central
Italy, the hard white stones became normal for masonry
that was to remain visible, while tuff was often retained in
foundations and other hidden parts. Standard work, for
instance the porticoes of the Pompeian forum (Fig 22),
was executed in limestone, especially the so-called lapis
Tiburtinus (travertine) quarried near Tivoli, while for the
more lavish buildings, especially temples, and for carved
decorative detail architects used white marble.
The situation in Roman Britain has been partially
examined by various writers, notably by Williams (1971)
for the south and east of the province. Much of the
masonry was cut in the most accessible varieties of
limestone, but other materials were used locally; for
example, red sandstone at Chester and greensand in parts
of Kent, Sussex, and Norfolk, and in London. Williams
points out that the regions where greensand was employed
outside its native area were those which could be served by
boar from a possible source or depot on the Medway, a
theory which is supported by the presence of building
stone of Kentish origin in the cargo of the Blackfriars boat.
Rarely in Britain does stone seem to have been used far
from its source; exceptions were made only where the
stone was of good quality and the building project of a
prestigious nature. For example, if Williams is correct,
Ham Hill stone from Somerset was brought to Colchester
for use in the Temple of Claudius. The most highlyrenowned
material in Britain, the so-called Purbeck
marble from Dorset, occurs only in shallow strata and was
therefore confined to small-scale work, such as inscription
slabs, ornamental pieces, and veneer; the largest items in
its repertory are carved capitals.
The techniques of handling and working good-quality
building stone varied little throughout antiquity, or
19
Ling: The mechanics of the building trade
indeed in more recent times before the advent of mechanization.
Quarrying is the first stage. Remains of various quarries,
both Greek and Roman, show that normally the
workers would cut into a face, proceeding from top to
bottom, so that for any given block only two main faces,
the rear and the underside, had to be freed from the living
rock. This was a natural way of economizing on labour. At
the same time care had to be taken to avoid fault-lines, the
devastating effects of which are attested by numerous
half-finished and abandoned pieces, both architectural
and sculptural. But, provided that all was well, a roughly
rectangular block would generally be procured. This was
done by cutting grooves or, alternatively, by drilling a
series of parallel holes along the proposed edges, then
using chisels and wedges to split the stone.
The next stage was transport. Some preliminary dressing
of the blocks could be undertaken by masons in the
quarry and certain elements, notably columns, were even
roughly shaped, as can be seen from the numerous
half-finished columns in the quarries of Carystus, but all
pieces were transported in an unfinished state to avoid
damage. Many examples of quarry blocks have been
found at Ostia, where they were doubtless awaiting
transfer from sea- to river-craft on their voyage to the
marble-yards of Rome; among them is a cipollino columnshaft
with a raised band at the end to protect the main part
from contact with the ground, and a series of blocks with a
curious arrangement of different-sized steps and offsets.
These bear no relation to any intended architectural role
and are best explained as a device to convert an irregular
shape, perhaps dictated by fault-lines in the quarry, into
one which could be more easily stored and at the same time
more easily measured for accounting purposes. Transport,
as the Ostian finds demonstrate, would be conducted
as far as possible by water; but there was always an
overland component, sometimes a long and difficult one,
between the quarries and the nearest river or port. This
was inevitably the most expensive and time-consuming
part of the journey. Small blocks were presumably carried
by ox-cart, but such methods were cumbersome and the
axles would have been hard put to stand the strain,
especially as the surfaces can rarely have been smooth; one
has only to read Carl Humann’s graphic account of his