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MEDIEVAL ENGLAND
staple of English trade from the twelfth century, is especially
interesting. The number of water-mills had steadily increased
in the west, regardless of political disturbances, since the fourth
century, and, in the eleventh century, Domesday Book records
some five thousand mills in England. In the twelfth century the
undershot wheel on a horizontal axle was the common type;
evidence for overshot wheels comes in the fourteenth century.
Such mills were used for grinding corn and other purposes, but
their most dramatic effect came at the end ofthe twelfth century
with the introduction of the fulling-mill, in which trip/hammers
were operated by a waterwheel. The cloth industry shifted
wholesale from the cities ofthe plain like York, Lincoln, Win
chester, and Oxford, into the hills ofthe West Riding, Cum
berland, and the Cotswolds, where fast streams were available
to drive the mills.
The first medieval machines were made of wood; this, in
Mumford's phrase, 'provided the finger exercises for the new
industrialism'. But machines of greater precision needed a
material susceptible of more accurate shaping, and this was
provided by the development of metallurgy. From the metal
lurgical, as well as the mathematical skill, first of Byzantium
and the Arabic east and eventually, from the twelfth century,
of the Latin west, came the earliest scientific instruments, the
astrolabes and other devices requiring an accurate arrangement
of parts, for measuring the movements of the heavenly bodies;
refinements of metallurgy gave the surgeon the instruments to
develop his art; and, at the endjof the thirteenth or the beginning
ofthe fourteenth centuries, the west produced, in the mechani
cal clock, the prototype ofmodern automatic machinery, with
parts designed to produce a precisely controlled result.
The mechanical clock, driven by a
falling weight which set
in motion a train of geared wheels, was the latest of a series of
time-keeping machines going back to the simple water-clocks
of antiquity; its originality consisted in the complete mastery it
showed of geared wheels and in the use ofan oscillatory escape
ment mechanism which controlled the rate of motion. There
are references to what may have been clocks of this kind in