EVIDENCE FOR WATER-POWERED TRIP-HAMMERS
The Plan of St. Gall contradicts these views. The pilae
of its Mortar House can under no circumstances be interpreted
as vertical pestles. Their design—a hammer attached
at right angles to a pestle beam connecting at the opposite
end with a body of cylindrical shape—leaves no doubt
that they were recumbent hammers activated by the cams
of a revolving drum. Their dimensions as well as their
location, next to a water-driven grain mill, suggests that
they were water powered. The pestle beam alone is 10 feet
long (4 standard modules), the hammer has a length of 6
feet (2½ standard modules) and the drum has a diameter
of 6¾ feet. The over-all length comes close to 17½ feet. This
is a very heavy piece of equipment that could not possibly
be operated by hand or foot. The Plan may somewhat
exaggerate the dimensions of the drum,[516]
but it leaves no
question about the presence of a drum, which makes sense
only within the context of a water-powered apparatus.
Marc Bloch's argument that water is not shown on the
Plan, does not militate against this conclusion. We have
shown in our chapter on omissions and oversights how
waterways, although nowhere in evidence on the Plan,
could be a determining factor in siting of facilities dependent
on this power source, and were therefore clearly a
possibility taken into account by the designing architect.
[517]
The crushing mechanisms of the Mortar House of the
Plan of St. Gall are, as far as I can see, the earliest historical
evidence of the use of hydraulic trip-hammers in Western
Europe. Their appearance on the Plan makes it clear that
water-driven trip-hammers were, at the time when the
original scheme was drawn, i.e., in 816-817, considered
standard equipment of a paradigmatic Carolingian monastery.
There is no reason to presume that the inventor of the
scheme was also the inventor of the mechanism. The
system as such may, even in Europe, have been of considerably
greater age. It may have been diffused in Frankish
times from China, as the stirrup certainly was, as the two
forms of modern horse-harnesses probably were, and as
the mechanical crank may have been.[518]
