Historical Development of the Windmill - Wind Turbine Technology: Fundamental Concepts of Wind Turbine Engineering - page 4

Ancient Times
The earliest mentions of the use of wind power come from the East: India, Tibet,
Afghanistan, Persia. Ancient manuscripts, however, have often suffered from mistransla-
tions, revisions, and interpolations by other hands over the centuries. In some, even
diagrams were changed to suit the whims of revisionists, and there are instances of
forgeries. Drachmann [1961], Needham [1965], Vowles [1930], and White [1962] all cite
examples of these aberrations. Marie Boas provides a good illustration of the treatment a
manuscript can undergo in her detailed monograph, “Hero's Pneumatica - A Study of its
Transmission and Inluence” [1949].
Mentioning the Boas monograph is apposite here because of the well-known ascription
of the invention of the windmill to Heron (a variant of Hero ) of Alexandria, by virtue of
his account of it as one of the many devices in his Pneumatica of 2,000 years ago. This
ascription is now discounted by most authorities in varying degrees, ranging from outright
rejection, through wistful reluctance to relinquish the idea, to acceptance as only a toy.
There is dificulty with respect to the provenance of a sketch in the Pneumatica and some
disagreement as to the exact meaning of certain key words. This story is reviewed here
because it is a classic example of the dificulty of making a positive attribution from an
ancient manuscript. Was Heron really the inventor of the windmill as a practical prime
mover, and was his invention the inspiration for those that followed, even though centuries
elapsed between the birth of the idea and its fulillment?
The exact dates of Heron's birth and death are not known. Surmises lie between the
second century B.C. and the third century A.D.; some time in the irst century A.D. is
perhaps the most probable. His Pneumatica (best known to many as the source of the
reaction steam turbine) consists of descriptions of various ingenious apparatuses that operate
on the basis of air or water; some of them are what we would now call toys or even
“magic” devices. He himself said that he added some of his own inventions, but he did
not say which ones they were. The topic was known and referred to in medieval times, but
many transcripts and translations into Latin or Greek have been lost either in whole or in
part. An English translation was provided by Bennett Woodcraft [1851] and a German one
by Wilhelm Schmidt [1899]. The latter contains the original Greek wording side by side
with the German, and it is generally accepted as a standard text.
The opening sentence in the relevant chapter in the Pneumatica is given by Woodcroft
as “the construction of an organ from which when the wind blows the sound of a lute shall
be produced.” Schmidt provides essentially the same translation in his German version.
Both contain diagrams [Figures 1-1(a) and (b)] showing a shaft with blades at one end and
four pegs at the other, the pegs intermittently striking a lever rod which then lifts a piston
contained in a cylinder. Between lifts, the piston falls in the cylinder of its own weight,
resulting in air being pumped to a musical organ. Although both drawings are based on the
description in the text, each suits the translator's own imagination: Woodcroft presents a
horizontal-axis rotor having four sails, a type unknown until the twelfth century, and
Schmidt shows a water-mill type of rotor, again from a much later era. But Schmidt does
discuss in his introduction a much cruder version of the rotor illustrated in Figure 1-1(c).
According to Drachmann [1961], who has made a detailed reassessment in recent years, this
is as close to the original sketch as we are likely to get. Vowles also discusses the
Pneumatica puzzle [1930] and shows four examples of transmogriied images from various
later manuscripts that help to confound the confusion.
In addition to the dificulty we have with the drawings of Heron's device, the ex-
act meaning of some of the words leaves us in doubt. Two prime examples are the word
anemurion , meaning a windmill or only a weathervane, and whether Heron uses the word