Economic Development and Urban Growth in the High Middle Ages 177sea, but windmills, a Persian invention introduced to
Europe at the end of the twelfth century, did not be-
come common until the fifteenth century.
Fuel was limited almost entirely to wood and char-
coal and was rarely used to generate power. Wood was
burned for cooking and to supply heat. In western
Europe, interior heating was usually accomplished, if at
all, with residual heat from cooking. Charcoal, an ex-
pensive commodity, was used primarily in the smelting
and forging of metals, while coal, first mentioned in
European sources around the year 1200, did not come
into general use for another four hundred years. This
was largely because mining techniques remained primi-
tive. In the absence of effective pumps the pits could
not be kept dry, and the development of effective
pumps depended upon metallurgical techniques that
were as yet unknown. Mine pumps also require a cheap,
reliable source of power because they must be worked
continuously. Windmills, used from the fifteenth cen-
tury onward to drain the tidal wetlands of Holland,
were a possible solution, but they proved ineffective in
hilly country or in regions where wind strength was in-
constant. None of these problems was fully solved until
the age of steam. In the meantime, coal and ores could
be mined only from shallow pits, and transportation
costs ensured that coal would be used only in the im-
mediate vicinity of the mines. The scarcity of metals
made ore worth transporting, but it was always best if
deposits were located near abundant sources of char-
coal so that smelting might occur on the spot.
Tools tended to be made of wood or of wood
tipped with iron. Alloy steel was unknown, and the
handwrought carbon steel used in knives and edged
weapons was expensive. The process required great
skill and enormous quantities of fuel. Even implements
made from lower grades of iron represented a major
capital outlay for farmers and artisans.
The high cost of iron resulted in part from the limi-
tations of mining technology, but skilled iron workers
were few in number, and the making of charcoal for use
in the forges consumed large quantities of wood. Wood
had long been scarce in the Mediterranean basin. By the
end of the Middle Ages its availability was limited in
northwest Europe as well. Only in the Baltic regions and
in eastern Europe was timber plentiful, and even there
prices increased steadily throughout the Middle Ages in
response to increased demand from other regions.
Given that wood was a primary building material as well
as the major source of fuel, this is hardly surprising.
Ships were built almost entirely of wood and con-
sumed vast quantities of the best timber. Their keels
and frames demanded rare, naturally curved compass
timbers, and their masts required tall, straight trees with
few branches. Planking was almost invariably of the
best available oak. However high the quality of plank-
ing, constant immersion in water and the ravages of
marine organisms ensured a maximum life of seven or
eight years before a ship’s timbers had to be replaced.
Given the hazards of navigation, many ships went to
the bottom long before such repairs could be made,
with even higher replacement costs as a result.
On land, most buildings were at least framed in
wood. Fully wooden structures had once been common
in northern Europe. By the twelfth century they were
already becoming rare outside of Scandinavia and the
Baltic. The growing cost of lumber was forcing builders
to construct walls out of cob, wattle and daub, or some
other combination of earth mixed with straw. Roofs
were usually thatched and floors were of earth or clay.
Only public buildings and the homes of the very rich
were built of stone and roofed with slate or tile. Ma-
sonry construction was more common in the Mediter-
ranean basin, although precious wood was used for
joists and roof beams.
The high cost of iron and wood was symptomatic
not only of scarcity but also of the problem of distance.
They were heavy and expensive to ship. Owing to po-
litical fragmentation and the decay of the Roman high-
way system, transportation was more arduous and
expensive than in antiquity. Besides raising shipping
costs in general, this made compensating for local
shortages or crop failures by importing goods from
other regions difficult. Shipping grain overland for two
hundred miles might raise its price by a factor of seven,
making it unaffordable to the poor even if they were
starving.
Land transport was generally conducted over roads
that were little more than tracks, choked with dust in
dry weather and mired axle-deep in mud when it
rained. If the mud froze, ruts made the highways im-
passable for wheeled vehicles. For this reason, people
traveled on foot or on horseback, and pack animals
were generally preferred to ox-driven carts except in
optimum conditions.
Water transport, if available, was more efficient
(see illustration 10.1). Many European rivers are naviga-
ble for much of their length. Boats, rafts, and barges be-
came increasingly important with the passage of time.
The sea remained the greatest highway of all, uniting
the peoples who lived along its shores. The Baltic, the
North Sea, and the Atlantic coasts were served by a
wide variety of ship types whose chief common feature
was the use of a square sail set amidships. This rig was
easy to handle and provided excellent performance