Environmental Engineering Reference
In-Depth Information
The Vertical-Axis Persian Windmill
There have been suggestions that the Tibetan prayer wheel was the inspiration for the
windmill, but although this is a possibility, the provenance of the prayer wheel itself is
very doubtful. The next chronological reference to the windmill that we have refers to the
seventh century, but the text itself appeared at least 200 years later. The story was well
known and was repeated by several writers in more than one version. The irst mention is
by Alı al-Tabarı (A.D. 834-927).
1
According to Needham [1965], the Caliph Omar was
murdered in the Islamic capital of Medina in A.D. 644 by a captured Persian techni-
cian/slave, Abu Lu'lu'a, who was bitter about the high taxes; he also claimed to be able to
build mills driven by the wind. This story was repeated by the geographer Alı al-Mas'udı
(c. A.D. 956), apparently in a slightly variant form in which the Caliph asked the Craftsman
if he had boasted about being able to build a mill driven by the wind, to which he received
the reply, “By God, I will build this mill of which the World will talk” [Wulff 1966].
Because it was orally transmitted over many years, and there is no record of it by any
writer around the time of Omar's death, the incident can be used only to lend some
plausibility to the possible existence of the windmill in the Islamic world in the middle of
the seventh century.
First Record of a Windmill
We now come to the irst accepted establishment of the use of windmills; this was in
the tenth century in Persia. It is documented by reliable writers and reinforced by ancient
drawings that correspond to the remains of old mills and to modern ones still in use. The
region is S¯st¯n in eastern Persia (in present-day Iran), which bordered on Afghanistan; al-
Mas'¯d¯ describes it as
“...the land of winds and sand. There the wind drives mills and raises water
from the streams, whereby gardens are irrigated. There is in the world, and God
alone knows it, no place where more frequent use is made of the winds.”
Al-Istakhr¯, also of about A.D. 950, provides a similar description as well as an interesting
account of how the inhabitants coped with a shifting dune. They enclosed it in a high fence
with a door in a lower part that allowed the wind to blow the sand away from the fence,
which adds credibility to their skill in mastering the windmill. The wind of S¯st¯n is
famous, or rather notorious, as it is said to reach 45 m/s (100 mph) and to blow at gale
force with little respite for four months in late spring and early summer [Bellew 1874;
Hedin 1910].
Some three hundred years later we have conirmation from the geographer al-Qazw¯n¯
(A.D. 1203-1283), who wrote
“There the wind is never still, so in reliance on it mills are erected; they do all
their corn grinding with these mills, it is a hot land and has mills which depend
on the utilization of the wind” [Wulff 1966].
1
Authors differ frequently as to spelling and diacritical marks in Arabian names. Here,
Needham's usage has been followed for consistency, and because he introduces all such
names given in this text.
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