Food Sources: Earth, Water, and Air - Food Culture and Health in Pre-Modern Islamic Societies - page 33

of their travel they empty into a channel.
The noria (sometimes confused with the
sāiya ) is a large wheel driven by water.
It is mounted on a horizontal axle over
a flowing stream so that the water strikes
the paddles that are set around its perime-
ter. The water is raised in pots attached to
its rim or in bucket-like compartments set
into the rim. The large norias at amāt
in Syria can still be seen today; the first
known mention of norias at amāt is by
Amad b. al-ayyib in 271/884-5.
The Vitruvian mill-wheel turns a verti-
cal gear-wheel that meshes with a hori-
zontal gear-wheel to which the driving
shaft is attached. The horizontal vaned
mill-wheel is fixed directly to the driv-
ing shaft; there are no gears. It cannot
be mounted directly in the stream since
the water must be directed on to its vanes
from a pipe or channel.
There can be no doubt that all these
machines were in continuous use in Islam
from the early conquests until the intro-
duction of modern technology. (As men-
tioned above, the ª ādūf and the ākiya
are still in use; they are cheaper and more
easily maintained than motor-driven
pumps.) The evidence comes from trea-
tises on machines, references in the works
of historians and geographers, and archae-
ological investigations. The remaining dis-
cussion will be confined to developments
of particular importance in the history of
technology.
Mills were used in Islam for other
purposes beside the grinding of corn
and other seeds, e.g. for crushing sugar
cane and for sawing timber. This sug-
gests that rotary motion was converted
to reciprocating, probably by means of
trip-hammers. More examples of similar
applications may be discovered when a
systematic study of the historical and geo-
graphical works is undertaken. Another
area of interest is the use of the overshot

mill-wheel, in which the water is con-
ducted through a channel to the top of
the wheel, which has bucket-like compart-
ments around its rim. The overshot wheel
works mainly by the weight of the water,
whereas the Vitruvian one is operated by
its force. In many conditions, the former
is the more efficient of the two. Its use
is recommended by a certain Murādī in
a treatise composed in Andalusia in the
5th/11th century. In this paper the trea-
tise was wrongly attributed to the well-
known astronomer Ibn Muā £ ). · ams
Dīn al-Dima ª ī, d. 727/1327, describes
a similar wheel in operation near Tabrīz.
The overshot wheel did not come into
general use in the West until about the
8th/14th century. Al- ⁄ azarī often uses
small overshot wheels in his devices, but
these are usually scoop-wheels, a kind of
primitive Pelton wheel, the scoops being
fixed to the ends of spokes that radiate
from a solid disc.
It is reasonable to infer that the scoop-
wheels used by al- ⁄ azarī were miniature
versions of wheels in full-size machines,
an inference that is strengthened by the
fact that he uses such a wheel in one of his
water-raising machines. The visible part
of this is a āiya , which is provided with
a model cow to give the impression that
this is the source of motive power. The
actual power, however, is provided in a
lower, concealed chamber and consists of
a scoop-wheel and two gear-wheels. This
system drives the vertical axle that passes
up into the main chamber, where two
further gear-wheels transmit the power
to the chain-of-pots wheel. Such devices
(without the model cow) were in everyday
use. A similar machine was in continuous
use on the River Yazīd above Damascus
from the 7th/13th century until about
1960 for water supply and irrigation. It
was restored to working order by the staff
and students of Aleppo University.