Dr. Meyerhof writes in "The Legacy of Islam" (P.132): "Muslim doctors laughed at
the Crusaders' medical attendants for their clumsy and elementary efforts. The
Europeans had not the advantage of the books of Avicenna, Jaber, Hassan bin
Haytham, Rhazes. However, they finally had them translated into Latin. These
translations exist still, without the translators' names. In the 16th century
the books of Averroes (Inb Rushd) and avicenna (Ibn Sina) were put out in Latin
translation in Italy and used as the basis of instruction in the Italian and
French universities."
On page 116 of the same work he writes that after Rhazes' death the works of
Avicenna (AD 980-1037) were taken up. His influence on thought and philosophy
and general science was profound, and his medical works (based on the works of
Galen which he had found in the Samarqand library in Arabic translation) had a
sensational outrech.
Other scientists followed - Abu'l-Qais of Andalusia; Ibn-Zahr of Andalusia;
Abbas the Irani; Ali ibn-Rezvan of Egypt; Ibn Butlan of Baghdad; Abu Mansur
Muwaffaq of Herat; Ibbn Wafeed of Spain; Masooya o Baghdad; Ali-ibn-Esau of
Baghdad; Ammar of Mosul; Ibn-Rushd (Averroes) of Andalusia; whose works were
translated into Latin were used in European universities. Europe knew nothing of
the cholera bacterium when Islam entered Spain, and the people there regarded
the disease as a punishment sent from heaven to exact the penalty of the sins:
but Muslim physicians had already proved that even the public plague was a
contagious disease and nothing else.
Dr. Meyerhof writes of Avicenna's book "The Canon" that it is a masterpiece of
medical science which proved its vworth by being printed in a series of 16
editions in the closing years of the 15th century AD, 15 Latin and one Arabic.
In the 16th century more than a score of further editions were published,
because of its value as a scientific work. Its use continued throughout the 17th
and 18th centuries, so that it became the most widely known of all medical
treatises. It is still consulted in medical schools.
Will Durant writes that Mohammad ibn Zachariah Razi (Rhazes) was one of Islam's
most progress physicians, author of 200 treatises and books well worth studying
today: in particular his
1. "Smallpox and Measles" (published in Latin and other European tounges in 40
editions between 1497 and 1866), and
2. "The Great Encyclopedia" 20 volumes mostly unobtainable nowadays: five
volumes were devoted to optics; translated into Latin AD 1279; printed in five
editions in 1542 alone; known as the most authoritative work on the eye and its
ailments and treatment for centuries; one of the nine basic works on which Paris
University composed its medical course in 1394 AD.
Surgery made similar progress in the hands of Islamic practitioners, who even
used anaesthetics, though theses are assumed to be of modern origin. They
employed a henbane base.
Among Rhazes' innovations was the use of cold water to treat persistent fever,
of dry-cupping for apoplexy, of mercury ointment and animal gut for wound
sutures, and many others.
Further information on Islamic medicine can be sought from the many books on the
subject. The diagnosis of tuberculosis from the fingernails, the cure of jundice,
the use of cold water to prevent haemorrage, the crushing of stones in bladder
and kidney to facilitate their removal, and surgery for hernia are among
advances too numerous to mention in detail. The greatest of the Islamic surgeons
was Abu'l Qasem of Andalusia, affectionately called Abu'l-Qays, and sometimes
Abu'l-Qasees, flourit 11th century AD, inventor of very many surgical
instruments and author of books to describe them and their uses -books
translated and printed in innumerable editions in Latin and used all over
Europe, the last such edition being in 1816.
II. Hospitals
Georgi Zeidan writes: "Within two centuries of the death of the Prophet, Mecca,
Medina and and other great Muslim cities all had hospitals, while the Abbasid
governors and their ministers competed each for his own region to have the best
such institution for the care of the sick. Baghdad alone had four important
hospitals. By three centuries after the hijra the governor Adhud-ud-Dowleh
Deylamy had founded the Adhudi Hospital with 24 specialists, each master of his
own particular field, a hospital which soon earned the reputation of excelling
all hospitals throughout Islam, though in the course of time it too was
surpassed.
The order and arrangement of Islamic hospitals was such that no distinctions of
race, religion or occupation were recognised, but cure was administered with
meticulous care to any patient. Separate wards were allotted for patients of
specific diseases. These were teaching hospitals where the students learned
theory and observed practice. In addition, There were travelling hospitals which
carried doctors and their gear by camel or mule to every district. Sultan
Mahmoud the Seljuk travelled with a hospital which required 40 camels for its
transport."
Dr. Gustave le Bon writes: "Muslim hospitals went in for preventive medicine and
the preservation of health as much as if not more than for the cure of the
already diseased. They were well-aired and had plenty of running water. Muhammad
bin Zachariah Razi (Razes) was ordered by the Sultan to seek out the healthiest
place in the Baghdad neighbourhood for the construction of a new hospital. He
visited every section of the town and its environs, and hung up a piece of meat
which he left while he looked into infectious diseases in the neighbourhood and
studied climatic conditions, particularly the state of the water. He balanced
all these various experimental tests and finally found them all to indicate that
the place where the portion of meat was the last to putrefy and develop
infectious bacteria was the spot on which to build. These hospitals had large
common wards and also private wards for individuals. Pupils were trained in
diagnosis and brought obserrvation and experience to the perfecting of their
studies. There were also special mental hospitals, and pharmacies which
dispensed prescriptions gratis."
Marc Kapp writes: "Cairo had a huge hospital with playing fountains and
flower-decked gardens and 40 large courtyards. Every unfortunate patient was
kindly received, and after his cure sent home with five gold coins. While
Cordoba, besides its 600 mosques and 900 hammams, had 50 hospitals."
III. Pharmacology
[Pharmacology, as many other branches of sciences, is considered by Europeans to
be an entirely new scientific field. In this respect, they feel, like ancient
tribes, that the world is limited to the horisons of their territory. One must
realize that this knowledge has mainly originated from the Middle East as well
as from China].
[In Europe, until recently,] there was a surprising reluctance to apply anything
resembling scientific principles to therapeutics. Even Robert Boyle, who laid
the scientific foundations of chemistry in the middle of the seventeenth
century, was content, when dealing with therapeutics (A Collection of Choice
Remedies, 1692), to describe and recommend a hotch-potch of messes consisting of
worms, dung, urine and the moss from a dead man's skull.
Gustave le Bon writes: "Besides the use of cold water to treat typhoid cases - a
treatment later abandoned, though Europe is taking this Muslim invention up
again in modern times after a lapse of centuries - Muslims invented the art of
mixing chemical medicaments in pills and solutions, many of which are in use to
this day, though some of them are claimed as wholly new inventions of our
present century by chemists unaware of their distinguished history. Islam had
dispensaries which filled prescriptions for patients gratis, and in part of
countries where no hospitals were reachable, physicians paid regular visits with
all the tools of their trade to look after public health."
Georgi Zeidan writes: "Modern European pharmacologists who have studied the
history of their profession find that Muslim doctors launched many of the modern
beneficial specifics centuries ago, made a science of pharmacology and compound
cures, and set up the first pharmacies on the modern model. So that Baghdad
alone had 60 chemists shops dispencing prescriptions regularly at the charges of
Caliph. Evidence of these facts can be seen in the names given in Europe to
quite a number of medicines and herbs which betray their Arabic, Indian or
Persian origin." Such are 'alcohol', 'alkaner', 'apricot', 'arsenic', to quote
some 'a's alone.
IV. Industry
The Abbasid Caliph Haroun-al-Rashid sent Charlemagne in Aix from Baghdad a
present of a clock made by his horologists which struck a bell on the hour very
hour, to the great wonder and delight of the whole court of the newly crowned
Holy Roman Emperor.
The massacre and expulsion of the Muslims of Andalusia by the Christians carried
with it the clousure of many of the great factories that has existed under
Islamic rule, and the standstill of progress that had been made in science,
crafts, arts, agriculture, and other products of civilization. Towns began to
fall into ruin because of the lack of skilled masons. Madrid dropped from
400,000 to 200,000 inhabitants: Seville, which had possessed 1,600 factories
under the Muslims, lost all but 300, and the 130,000 workers formerly employed
had no more jobs, while the census of Philip IV showed a fall of 75% in
population figures.
It was the Muslims also who brought about the substitution of cotton-wove paper
for the old parchments; and it was this invention which formed the basis for
Europe's later invention of printing, using an old Chinese technique, and so for
the vast uprush of learning which came with the Renaissance. More, since monks
were starved for parchment on which to write their religious works, they were
tending more and more to scrape off priceless ancient scientific texts from old
parchments and to use them again as palimpsets. The introduction of paper put a
stop to this disastrous practice in time to save quite a number of texts which
would have otherwise been lost for ever, as, alas, too many were.
A paper manuscript of the year AD 1009 was found in the Escorial library, and
claims to be the oldest hand-written book on paper still in existence. Silk-wove
paper, of course, was a Chinese invention, since silk was native to China though
rare in Europe; and the Musulman genius lay in seeing the possibility of
substituting cotton for silk, and so giving Europe a plentiful supply of a
practicable material for the reproduction of books by the monkish scribes.
Philip Hitti writes in his "History of the Arabs" that the art of road-making
was so well developed in Islamic lands that Cordova had miles of paved road lit
from the houses on each side at night so that people walked in safety; while in
London or Paris anyone who ventured out on a rainy night sank up to his ankles
in mud - and did so for seven centuries after Cordova was paved! Oxford men then
held that bathing was an idolatrous practice; while Cordovan students revelled
in luxurious public hammams!
V. Geography
The Arabian Nights' tales of Sindbad the Sailor, and of his voyages to China,
Japan, and the Spice Islands of Indonesia, give quite enough evidence of the
brilliance of Arabic commercial shipping and the knowledge of meteorology and
geography which was at their disposal. Small wonder that the Faith spread
through them from Morocco to Mindanao.
But, besides the SE Asian seas, arabic sailors penetrated far down the East
coast of Africa, and also up the rivers which are channels from the Black Sea
into the distant interior of Russia. The Safarname (Travel journal) of Suleiman,
a sea-captain of Seraf, the port on the Persian Gulf recently excavated by Dr.
David Stronach of the British Institute of Persian Studies, was published at the
end of the 9th century AD with accounts of his voyages to India and China. It
was translated into Latin, as giving some of the earliest first-hand knowledge
of China which ever reached Europe.
The geographer Ibn Hauqal (floruit circa AD 975) wrote in his preface: "I have
written the latitude and longitude of the places of this earth, of all its
countries, with their boundaries, and the dominions of Islam, with acareful map
of each section on which I have marked numerous places, e.g. the cities, the
kasbahs, the rivers, the lakes, the crops, the types of agriculture, the roads,
the distances between place and place, the goods for commerce and everything
else in the science of geography which can be useful to sovereigns and their
ministers and interesting to all people in general.
Abu-Reihan al-Biruni, Ibn Batuta and Abu'l-Haussan are amongst other names in
the history of the science of geography whose worldwide travels were accompanied
by meticulous observation and painstaking notes, which are amongst the proudest
achievements of science in our world to this day.
VI. Chemistry
Jaber ibn Haiyan, disciple of the sixth Imam Ja'afar-i-Sadeq, became known
world-wide as "the Father of Chemistry" and of Arab alchemy. His influence on
western chemistry and alchemy was profound and long-lasting. Some hundred of his
works survive. Of him the late Sayyid Hebbat-ud-Din Shahristani of Kadhemain,
once Iraq's Minister of Education, writes: "I have seen some 50 ancient MSS of
works of Jaber all dedicated to his master Imam Ja'afar. More than 500 of his
works have been put into print and are for the most part to be found among the
treasures of the National libraries of Paris and Berlin, while the savants of
Europe nickname him affectionately 'Wisdom's Professor' and attribute to him the
discovery of 19 of the elements with their specific weights, etc. Jaber says all
can be traced back to simple basic particle composed of a charge of lightning
(electricity) and fire, the atom, or smallest indivisible unit of matter, very
close to modern atomic science.
The blending of colouring matters, dyeing, extraction of minerals and metals,
steelmaking, tanning, were amongst industrial techniques of which the Muslims
were early masters. They produced Nitric Acid, Sulphoric acid, Nitro-glycerin,
Hydrochloric Acid, Potassium, Aqua Ammonia, Sal Ammoniac, Silver Nitrate,
Sulphoric Chloride, Potassium Nitrate, Alcohol, Alkali (both still known by
their Arabic names), Orpiment (yellow tri-sulphide of arsenic; arsenic is
derived from the Persian zar = gold, adjective zarnee = golden, Arabised with
article "al" to "al-zernee" pronounced "azzernee" and so taken into Greek where
was turned to the recognizable word "arsenikon" which means "masculine" since
the gold colour was supposed to link it with the sun, a musculine diety!): and
finally - though this does not close the list we might cite - Borax, also an
Arabic word - Booraq. Further, the arts of distilling, evaporation, sublimation,
and the use of Sodium, Carbon, Potassium Carbonate, Chloride, and Ammonium were
common under the Abbasid Caliphate.
VII. Mathematics
Baron Carra de Vaux, author of the chapter on "Astronomy and Mathematics" in
"The Legacy of Islam" (OUP 1931 pp. 376-398), points out that the word "algebra"
is a Latinisation of the Arabic term Al-jabr (= "i.e. of complicated numbers to
a simpler language of symbols)., thereby revealing the debt the world owes to
the Arabs for this invention. Furthermore the numerals that are used are "Arabic
numerals" not merely in name but also in fact. Above all Arabs' realisation of
the value of the Hindu symbol for zero laid the foundation of all our modern
computerised technology. The word "zero", like its cousin "cipher" are both
attempts at transliterating the Arabic "sefr", in order to convoy into Europethe
reality and the meaning of that word in Arabic.
De Vaux writes: "By using ciphers the Arabs became the founders of the
arithmetic of everyday life; they mada algebra an exact science and developed it
considerably; they laid the foundations of analytical geometry; they were
indisputably the founders of plane and spherical trigonometry. The astrolabe (safeeha)
was invented by the Arab Al-Zarqali (Arzachel) who lived in Spain AD 1029-1087.
The word "algorism" is a latinisation of the name of his home province
Al-Khwarizmi. The Arabs kept alive the higher intellectual life and the study of
science in a period when the Christian West was fighting desperately with
barbarism".
This is not the place to go further into Muslim achievements in mathimatics and
astronomy. Suffice it to refer once again to the Jalali calendar of Omar
Khayyam, with its formulae for exact calculation of the timing of the earth's
orbits round the sun, to which reference has been made earlier.
VIII. Art
Cordova Mosque is one of the finest monuments of Muslim art in Europe. Its
architect and masons were local talent, who introduced a number of novelties.
The Muslims excelled at mosaic, inlay, fretwork and applique work of all types.
Marvellous doors, pulpits, and ceilings are decorated in many of the ancient
mosques all over the Muslim world with a lacelike design of mosaic, carved
invory and wood and plaster, and fitted pieces of carved wood interlocking with
each other with consummate artistry. Chased and engraved wood and ivory are
everywhere. Thus the Altar of the Church of Saint Isidore Hispalensis
(archbishop of Seville in the first years of the 7th century AD) like the carved
ivory jewel-case made for Queen Isabella in the 11th century and the carved
ivory box now in the Church at Bayeux of the 12th century (obviously some
Crusader's loot from the East) inlaid with silver in chased gold, are examples
of that art which was the glory of Eastern lands. All this delicate and minute
handiwork was carried out with the crudest and roughest of tools, itself a
further tribute to the skill and artistry of the makers.
Jewel-studded boxes and cases and caskets are to be seen in many places, though
the best are on view in the museums of Damascus and Cairo. Well said Sa'adi: "An
Eastern artist may take 40 years to make one porcelain vase: the West turns out
100 a day, all like: the comparative worth of the two products can be easily
reckoned!"
The Muslims were also past masters of the art of carved and coloured plaster
work, in a style which still subsists though modern technologies are, alas,
rendering the skill rarer all the time. Tenth century examples, some with
enamelled work also, are to be found in Andalusia. The Alhambra has 13th century
masterpieces of this work. The glitter like the later Italian Majolica. The
famous Alhambra flower-vase, 1.5 metres high, is unique in this line.
IX. Mechanical Engineering
About the author
Donald R. Hill, a retired engineer, became interested in Arabic while serving
with Britain's Eighth Army in North africa during World War II. After the war,
he worked for the Iraq Pertoleum Company, returning to England to join Imperyal
Chemical Industries. He later moved to senior positions in the subsidiaries of
two U.S. petrochemical corporations, from which he retired in 1984. He now
devotes his time to Arabic studies, in which he has earned a master's degree
from Durham University and a Ph.D. from the University of London's School of
Oriental and African studies. His translation of al-Jazari's book of mechines
won for him a share of the 1974 Dexter Prize, awarded by the American Society
for the History of Technology.
Preface
The West is accustomed to seeing its own intellectual development as having been
shaped, in the main, by internal factors. This view of history traces our
heritage back from the Industrial Revolution to the Enlightenment and
Renaissance and, thence, via the monkish scribes of the Middle Ages, to the
fountainhead: Greece, Rome and the ancient empires of the Fertile Crescent.
But the picture is incomplete because it ignores the intermediation of the
civilization of Greek Christendom (or Byzantium), Hindu India, Confucian China
and Islam. Our subject here is the technology of medieval Islam - the knowledge
it preserved, the new ideas it contributed to the medieval world and the
inventions by which it anticipated later developments.
When the prophet Muhammad died in A.D. 632, he left behind a new religion with
its administrative centre at Medina and its spiritual heart at Mecca. Within
about a year of his death the rest of Arabia had joined the Muslim fold; by 750
the Arab Empire stretched from the Pyrenees to central Asia.
Although the advent of Islam brought immense political, religious and cultural
changes, the technological traditions were largely unaffected. In mechanical
engineering the Muslims adapted the techniques of earlier civilizations to
satisfy the needs of the new society. These needs centered on a city life more
extensive than any seen since Roman times.
Baghdad's population is estimated to have reached about 1.5 million in the 10th
century, and cities such as Cordoba, Cairo and Samarkand, although smaller, were
still of considerable magnitude. Paris, by contrast, would not number 100,000
souls for another 400 years. Feeding and clothing the inhabitants of the Islamic
world's vast urban centers placed great demands on agriculture and distribution.
These, in turn, depended on technology for supplying irrigation water to the
fields and for processing the crops into foodstuffs.
Water and water power, therefore, will constitute our first concern. Then we
shall describe water mills. Finally, we shall turn to descriptions, most of them
in a handful of treatises that have come down to us, of water clocks, fountains
and various automata, some of which might seem trivial to modern eyes. Yet they
exploit concepts, components and techniques that did not enter the armamentarium
of European engineering until the time of the Renaissance.
The most ancient water-raising machine is the shaduf, a counterweighted lever
from which a bucket is suspended into a well or stream. It appears in
illustrations from as early as 2500 B.C. in Akkadin reliefs and is still in use
today in parts of the Middle East. Other traditional water-raising machines,
introduced between the third and first centuries B.C., include the screw, or
water snail, whose invention is attributed to the great mathematician Archemides.
It consists of a helical wooden blade rotating within a barrellike wooden
cylinder, a design that could not push water up inclines greater than about 30
degrees, although 20 degrees was more common.
Higher lift was achieved by the noria, a large wheel driven by the velocity of
the current. On the outer rim a series of compartments are fitted in between a
series of paddles that dip into the water and provide the propulsive power. The
water is scooped up by the compartments, or pots, and is discharged into a head
tank or an aqueduct at the top of the wheel. Norias could be made quite large.
The well-known whells at Hama on the river Orontes in Syria have a diameter of
about 20 meters. The noria is self-acting, and its operation thus requires the
presence of neither man nor beast. It is, however, expensive to build and
maintain.
The "saqiya" is probably the most widespread and useful of all the water-raising
machines that medieval Islam inherited and improved. It is a chain of pots
driven by one or two animals by means of a pair of gears. The animals push a
drawbar through a circle, turning an axle whose pinion meshes with a vertical
gear. The gear carries a bearing for the chain of pots, or pot garland - two
ropes between which earthenware pots are suspended. The chain of pots is optimal
for raising comparatively small amounts of water from comparatively deep wells.
Other mechanisms, however, were required to raise large quantities of water
relatively small distances. The problem can be solved by using a spiral scoop
wheel, which raises water to the ground level with a high degree of efficiency.
The machine is very popular in Egypt nowadays, and engineers at a research
laboratory near Cairo have been trying to improve the shape of the scoop in
order to achieve the maximal output. Although it appears very modern in design,
this is not the case; a 12th-century miniature from Baghdad shows a spiral scoop
wheel driven by two oxen.
These machines are still in use in many oil-poor middle eastern countries,
because for many purposes they are at least as efficient as diesel-driven pumps.
Moreover, they do not require imported fuels, spare parts or labor. Vital time
can therefore be saved, when the loss of even a single day's operation of a
machine can kill a crop, making reliable performance literally a matter of life
and death.
Given the importance of water-raising devices to the economy of many Islamic
societies, it is hardly surprising that attempts were made to introduce new
designs or modify existing ones. Some of the most interesting innovations are
found in one section of Ibn al-Razzaz al-Jazari's great book, The book of
knowledge of Ingenious Mechanical Devices, which was completed in Diyar Bakr in
Upper Mesopotamia in 1206 AD.
From our point of view, the most significant aspect of these machines is the
ideas and components that they embody. For example, one of them is explicitly
designed to eliminate out-of-balance loading and so produce a smoother
operation. Another incorporates a crank, the first known example of the
non-manual use of this important component. Some of these devices functioned as
curiosities.
The invention containing the most features of relevance for the development of
mechanical design, however, was intended as a practical machine for high-lift
duties: a twin cylinder, water-driven pump. A stream turned a paddle wheel
meshing with a horisontal gear wheel, which was installed above a sump that
drained into the stream. The horisontal wheel contained a slot into which a
vertical pin fitted near the perimeter of the wheel.
The turning wheel moved two connecting rods back and forth, thus driving
opposing pistons made of copper disks spaced about six centimeters apart, the
gap being packed with hemp. The pistons entered copper cylinders, each one
having a suction and delivery pipe. One piston began its suction stroke while
the other began its delivery stroke. This machine is remarkable for three
reasons: it incorporates an effective means of converting rotary into
reciprocating motion, it makes use of the double-acting principle and it is the
first pump known to have had true suction pipes.
Waterpower was clearly a prominent concern of medieval Islamic planners.
Whenever they mentioned a stream or river, for example, they often included an
estimate of how many mills it would operate. One might say that they assessed
streams for "mill powe"
WATERMILLS
The three main types of waterwheel had all been in existence since Classical
times - the horisontal wheel and two variations of the vertical wheel. The
horisontal wheel has vanes protruding from a wooden rotor, onto which a jet of
water is directed. In modern Europe the design was altered to use water moving
axially, like air flowing through a pinwheel, creating the water turbine.
Interestingly, wheels with curved blades onto which the flow was directed
axially are described in an Arabic treatise of the ninth century.
The more powerful vertical wheels came in two designs: undershot and overshot.
The former is a paddle wheel that turns under the impulse of the current. The
overshot wheel receives water from above, often from specially constructed
channels; it thus adds the impetus of gravity to that of the current.
When the levels of rivers fall in the dry season, and their flow diminishes,
undershot wheels lose some of their power. Indeed, if they are fixed to the
banks of rivers, their paddles may cease to be immersed. One way this problem
was avoided by mounting the waterwheels on the piers of bridges and taking
advantage of the increased flow there. Another common solution was provided by
the shipmill, powered by undershot wheels mounted on the sides of ships moored
in midstream. On the rivers Tigris and Euphrates in the 10th century, in Upper
Mesopotamia, which was the granary for Baghdad, enormous shipmills made of teak
and iron could produce 10 tons of flour from corn in every 24-hour period.
Gristmilling - the grinding of corn and other seeds to produce meal - was always
the most important function of mills. Mills were, however, put to many other
industrial uses. Among these applications were the fulling of cloth, the
crushing of mettalic ores prior to the extraction process, rice husking, paper
making and the pulping of sugarcane. The usual method of adapting waterwheels
for such purposes was to extend the axle and fit cams to it. The cams caused
trip-hammers to be raised and then released to fall on the material.
WINDMILLS
Where waterpower was scarce, the Muslims had recourse to the wind. Indeed it was
in riverless Seistan, now in the western part of Afghanistan, that windmills
were invented, probably early in the seventh century A.D. The mills were
supported on substructures built for the purpose or on the towers of castles or
the tops of hills. They consisted of an upper chamber for the millstones and a
lower one for the rotor. A vertical axle carried either 12 or six rotor blades,
each covered with a double skin of fabric. Funnel-shaped ducts pierced the walls
of the lower chamber, their narrower ends facing toward the interior in order to
increase the speed of the wind when it flowed against the sails.
This type of windmill spread throughout the Islamic world and thence China and
India. In medieval Egypt it was used in the sugarcane industry, but its main
application was to gristmilling.
FINE TECHNOLOGY
Now we turn to a type of engineering that is quite different from the
utilitarian technology described so far. We may perhaps call it fine technology,
since its distinguishing features derive from the use of delicate mechanisms and
controls.
Some of these devices had obvious practical uses: water clocks were used in
astronomical observations and were also erected in public places; astronomical
instruments aided both observation and computation. Other gave amusement and
aesthetic pleasure to the members of courtly circles. Still others undoubtedly
had didactic purposes, for example, to demonstrate the principles of pneumatics
as understood at the time. Apart from astronomical instruments and the remains
of two large water clocks in Fez, Morocco, none of theses machines has survived.
Our knowledge of them comes almost entirely from two of Arabic treatises that
have come down to us.
The first is by the Bano (Arabic for sons of) Musa, three brothers who lived in
Baghdad in the ninth century. They were patrons of scholars and translators as
well as eminent scientists and engineers in their own right. They undertook
public works and geodetic surveys and wrote a number of books on mathematical
and scientific subjects, only three of which have survived.
The one that concerns us here is "The Book of Ingenious Devices". It contains
descriptions, each with an illustration, of 100 devices, some 80 of which are
trick vessels of various kinds. There are also fountains that change shape at
intervals, a "hurricane" lamp, self-trimming and self-feeding lamps, a gas mask
for use in polluted wells and a grab for recovering objects from the beds of
streams. This last is of exactly the same construction as a modern clamshell
grab.
The trick vessels have a variety of different effects. For example, a single
outlet pipe in a vessel might pour out first wine, then water and finally a
mixture of the two. Although it cannot be claimed that the results are
important, the means by which they were obtained are of great significance for
the history of engineering. The Banu Musa were masters in the exploitation of
small variations in aerostatic and hydrostatic pressures and in using conical
valves as "in-line" components in flow systems, the first known use of conical
valves as automatic controllers.
In several of these vessels, one can withdraw small quantities of liquid
repeatedly, but if one withdraws a large quantity, no further extractions are
possible. In modern terms, one would call the method used to achieve this result
a fail-safe system.
The second major treatise to have come down to modern times was written by al-Jazari
at the close of the 12th century. He was a servant of the Artuqid princes,
vasals of Saladin (who vanquished Richard the Lion Heart during the Third
Crusade). His work places him in the front rank of mechanical engineers from any
cultural region in pre-Renaissance times.
Several of al-Jazary's machines have been reconstructed by modern craftsmen
working from his specifications, which provided far more detail than was
customary in the days before patent law was invented. Such openness has rarely
been encountered until recent times.
WATER CLOCKS
Al-Jazari's clocks all employed automata to mark the passage of the hours. These
included birds that discharged pellets from their beaks onto cymblas , doors
that opened to reveal the figures of humans, rotating Zodiac circles, the
figures of musicians who struck drums or played trumpets and so on. Generally
speaking, the prime movers transmitted power to these automata by means of
pulley systems and tripping mechanisms. In the largest of the water clocks,
which had a working face of about 11 feet high by 4.5 feet wide, the drive came
from the steady descent of a heavy float in a circular reservoir.
Clearly, some means of maintaining a constant outflow from the reservoir was
needed and was indeed achieved in a most remarkable way. Apipe made of cast
bronze led out from the bottom of the tap, and its end was bent down at right
angles and formed into the seat of a conical valve. Directly below this outlet
sat a small cylindrical vessel in which there bobbed a float with the valve plug
on its upper surface.
When the tap opened, water ran into the float chamber, the float rose and caused
a plug to enter the valve's seat. Water was thus discharged from a pipe at the
bottom of the float chamber, and the valve opened momentarily, whereupon water
entered from the reservoir, the valve closed momentarily and so on. An almost
constant head was therefore maintained in the float chamber by feedback control,
and the large float in the reservoir descended at constant speed. Al-Jazari said
he got the idea for his invention from a simpler version which he attributed to
Archimedes.
This clock did not record equal hours of 60 minutes each, but temporal hours,
that is to say, the hours of daylight or darkness were divided by 12 to give
hours that varied with the seasons. This measurement required another piece of
equipment: the pipe from the float chamber leading into a flow regulator, a
device that allowed the orifice to be turned through a complete circle and thus
to vary the static head below the surface of the water in the reservoir.
Previous flow regulators had all been inaccurate , but al-Jazari describes how
he calibrated the instrument accurately by painstaking tial-and-error methods.
Another type of clock, which may have been al-Jazari's own invention,
incorporates a closed-loop system: the clock worked as long as it was kept
loaded with metal balls with which to strike a gong.
CANDLE CLOCKS
Al-Jazari also describes candle clocks, which all worked on a similar principle.
Each design specified a large candle of uniform cross section and known weight
(they even laid down the weight of the wick). The candle was installed inside a
metal sheath, to which a cap was fitted. The cap was made absolutely flat by
turning it on a lathe; it had a hole in the centre, around which, on the upper
side, was an indentation.
The candle, whose rate of burning was known, bore against the underside of the
cap, and its wick passed through the hole. Wax collected in the indentation and
could be removed periodically so that it did not interfere with steady burning.
The bottom of the candle rested in a shallow dish that had a ring on its side
connected through pulleys to a counterweight. As the candle burned away, the
weight pushed it upward at a constant speed. The automata were operated from the
dish at the bottom of the candle. No other candle clocks of this sophistication
are known.
MISCELLANEOUS
Other chapters of al-Jazari's work describe fountains and musical automata,
which are of interest mainly because in them the flow of water alternated from
one large tank to another at hourly or half-hourly intervals. Several ingenious
devices for hydraulic switching were used to achieve this operation. Mechanical
controls are also described in chapters dealing with a potpourri of devices,
including a large metal door, a combination lock and a lock with four bolts.
We see for the first time in al-Jazari's work several concepts important for
both design and construction: the lamination of timber to minimize warping, the
static balancing of wheels, the use of wooden templates (a kind of pattern), the
use of paper models to establish designs, the calibration of orifices, the
grinding of the seats and plugs of valves together with emery powder to obtain a
watertight fit, and the casting of metals in closed mold boxes with sand.
CONCLUSIONS
Previously how Islamic mechanical technology entered Europe is unknown. Indeed,
there may be instances of ideas being inherited directly from the Greco-Roman
tradition into medieval Europe. Nor can we rule out cases of reinvention. When
allowances have been made, however, it seems probable that some elements of the
rich vein of Islamic mechanical engineering were transmitted to Europe.
Any such technological borrowing would probably have been mediated by contacts
between craftsmen, by the inspection of existing machines working or in
disrepair and by the reports of travelers. The most likely location for the
transfer of information was Iberia during the long years in which Christians and
Muslims coexisted.
The diffusion of the elements of machine technology from lands of Islam to
Europe may always remain partly conjectural. This should not in any way be
allowed to devalue the achievements of the Muslim engineers, known and
anonymous. Nor should we overemphasize the relevance of the Islamic inventions
to modern machinery. Of equal or great importance is the contribution they made
to the material wealth, and hence the cultural riches, of the medieval Near
East.
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