Windmills

Introduction of Wind Power

During the reign of Caliph Ummar (634-44) began the use of wind as a source of power in Islam. A Persian came to the Caliph and said he could build a mill operated by wind, so the Caliph ordered him to have one built. Wind-power became widely used in Islam to run mill stones for grinding corn, and also to draw up water for irrigation. Descriptions and drawings of Islamic windmills exist in a large abundance.

`A millstone is attached to the end of a wooden cylinder, half a metre wide, and 3.5 to 4 metres high, standing vertically in a tower open on the north east side to catch the wind blowing from this direction. The cylinder has sails made of bundles of ush or palm leaves (which reminds of the modern European windmill), attached to the shaft of the axle. The wind, blowing into the tower, exerts strong pressure on the sails, so turning the shaft and millstone.'

The windmills were erected on substructures built for the purpose, or on the tower of castles or on hilltops. Early windmills for grinding corn were, indeed, two storey buildings; in the upper storey were placed the millstones, and in the lower one, a wheel driven by the sails-six or twelve in number and covered with fabric-which turned the upper millstone. The walls of the lower chamber were pierced by four vents with the narrower end towards the interior, like the loopholes of a fortress so as to direct the wind on to the sails, and increase its speed.

In Europe, the oldest text in relation to windmills is a French act of 1105 granting a religious community the right to establish one of these apparatuses, called molendinam ad ventum (moulin a vent in French: windmill in English).

by: FSTC Limited, Fri 10 January, 2003

Muslim Engineer

Al-Jazari - the Mechanical Genius
by: Foundation for Science Technology and Civilisation. Info@fstc.co.uk

By Prof. STS Al-Hassani, UMIST, Manchester, UK.
Al-Jazari was the most outstanding Mechanical Engineer of his time. His full name was Badi Al-Zaman AbulI-Ezz Ibn Ismail Ibn Al-Razzaz Al-Jazari and he lived in Diyar-Bakir (in Turkey) during the 6th century AH (12th century CE).

He was called Al-Jazari after the place of his birth, Al-Jazira, the area lying between the Tigris and the Euphrates in Iraq. Like his father before him he served Urtuq kings of Diyar-Bakir, from 570-597 AH (1174-1200 CE) as a Mechanical Engineer. In 1206 he completed an outstanding book on engineering entitled "Al-Jami Bain Al-Ilm Wal-Amal Al-Nafi Fi Sinat'at Al-Hiyal" in Arabic. It was a compendium of theoretical and practical mechanics. Writes Sarton (1884-1956):"This treatise is the most elaborate of its kind and may be considered the climax of this line of Muslim achievement." Sarton vol.2; page 510.

Al-Jazari's book is distinctive in its practical aspect because the author was a competent engineer and skilled craftsman. The book describes various devices in minute detail hence an invaluable contribution in the history of engineering. British charter engineer Donald Hill (1974) who has a special interest in Arab technology writes:

"It is impossible to over emphasize the importance of Al-Jazari's work in the history of engineering, it provides a wealth of instructions for design, manufacture and assembly of machines."

Al-Jazari describes fifty mechanical devices in six different categories, including water clocks, hand washing device (wadu machine) and machines for raising water etc. Following the "World of Islam Festival" held in the United Kingdom in 1976 a tribute was paid to Al-Jazri when the london Science Museum showed a successfully reconstructed working model of his famous "Water Clock."

Hill translated Al-Jazari's work in 1974, seven centuries and 68 years after it was completed by its author. Al-Jazari's book includes six main categories of machines and devices. Several of the machines, mechanisms and techniques that first appear in this treatise, later entering the vocabulary of European mechanical engineering, including double acting pumps with suction pipes and the use of a crank shaft in a machine, accurate calibration of orifices, lamination of timber to reduce warping, static balancing of wheels, use of paper models to establish a design, casting of metals in closed mould boxes with green sand etc. Al-Jazari also describes methods of construction and assembly in scrupulous detail of the fifty or so machines in it to enable future craftsmen to reconstruct them.

And he was successful in that, for many of his devices were constructed following his instructions. The work by al-Jazari is also unique in the way that other writers often fail to give sufficient details, because amongst others, they are not craftsmen themselves, or kept their secrets, or if they were craftsmen, they could have been illiterate. Al-Jazari in this respect was unique, and this gives his work immense value. His book, Hill states, is an absolute wealth of Islamic mechanical engineering.

In their paper in the charter Engineer of the I.Mech.E., Ludlow and Bahrani have raised the important point that it is more than likely that there is more on the subject in some of the thousands of Arabic manuscripts in the European and North American libraries which have been inspected closely, and obviously require looking into.
Hill, too, and constantly raises the two major issues with respect to the history of engineering in general, and that of fine technology in particular. He first states the fact that the field, which is absolutely immense, is yet totally unexplored.

The other issue is related to fine technology. One of his concluding points states that `it is hoped that, as research proceeds, firmer evidence for the transmission of Islamic fine technology into Europe can be provided.' Hill also offers some hints for such transmission. The most likely route being Spain. Such fine technology could have followed the same route as the astrolabe (itself part of this fine technology.) Apart from Spain, there was Sicily, another land of transfer, Byzantium, and Syria during the Crusades. And Hill is also right on a further account, that what will be seen in this work is just a fraction of the whole process, which, as with much else has hardly been explored.

The animation shows a virtual model of one of al-Jazari's water raising pumps. The details of this unique pump were obtained from his manuscript and Hill's diagrams. We see two suction pumps in synchronous motion driven by a paddle wheel, which is driven by a water stream.
The other animation is for a 3D model recreated from the description of the elephant clock as described by Al-Jazari. Full details of this animation are given in the book by Prof. S T S Al-Hassani on "The History of Muslim Engineering", to be published.

by: Professor Salim Al-Hassani, Fri 09 February, 2001

Dam and Water Management

Dam Construction
Summarised extracts from a full article, see resources below, where end notes, references and bibliography are given.
by: Foundation for Science Technology and Civilisation. Info@fstc.co.uk

In his `History of Dams,' Norman Smith, began his chapter devoted to Muslim dams,(endnote 1) by stating that:
`Historians of civil engineering have almost totally ignored the Muslim period, and in particular historians of dam building, such as there have been, either make no reference to Moslem work at all or, even worse, claim that during Umayyad and Abbasid times dam building, irrigation and other engineering activities suffered sharp decline and eventual extinction. Such view is both unjust and untrue.'(endnote 2)

Similar point is raised by Pacey, who notes that it is often said that hydraulic engineering `made little progress under the Muslim,' and that the latter's achievements hardly evolved beyond the Greek or Roman's. Pacey corrects this view, pointing out that the Islamic civilisation adapted ancient techniques `to serve the needs of a new age,' and that the Muslims extended the application of mechanical and hydraulic technology enormously.(endnote 3) To explain the reasons behind the belittling Muslim achievements as observed by Smith, Pacey and others(endnote 4) is a mammoth a task which requires people versed in political, religious, and historical matters.

Dams and Construction Techniques

The Muslims built many dams in a rich variety of structures and forms. The majority of the earliest Muslim dams were completed in Arabia itself; and full information on their height, length, and ratios between height and length is given by Schnitter. He also specifies that with the exception of the Qusaybah dam near Medina, a 30 m high-205 m long structure, which was slightly curved in plan, the alignment of all others were straight.(endnote 5) About half such dams were provided with a flood overflow at one end, and often with a downstream training wall to guide the spilled water to a safe distance from the dam's foot. Schnitter also observes that about a third of such very early dams (7th-8th century) are still intact.(endnote 6) In Iraq, in the vicinity of Baghdad, a considerable number of dams were built during the Abbasid Khalifate.(endnote 7) Most such dams are on the Tigris, but a few are on water diversions, further illustration of high engineering skills. In Iran can be found the Kebar dam, dating from the 13th century, the oldest arched dam known to have survived.(endnote 8) The dam has a core of rubble masonry set in mortar, the mortar made from lime crushed with the ash of a local desert plant, the addition of ash making the lime hydraulic. This resulted in a strong, hard and impervious mortar, ideal for dams, the very reason for such dam's long life, and the absence of cracks in it. Much earlier than this dam, in today's Afghanistan, were three dams completed by King Mahmoud of Ghaznah (998-1030) near his capital city. One named after him, was located 100 km SW of Kabul, and was 32m high, and 220m long.(endnote 9)

Dam construction in Muslim Spain was prolific. In the city of Cordoba, on the river Guadalquivir, can be found what is probably the oldest surviving Islamic dam in the country.(endnote 10) According to the twelfth- century geographer al-Idrisi it was built of Qibtiyya stone and incorporated marble pillars.(endnote 11) The dam follows a zig-zag course across the river, a shape which indicates that the builders were aiming at a long crest in order to increase its overflow capacity. Remains of the dam can still be seen today, a few feet above the river bed, although in its prime, it was probably about seven or eight feet above high- water level and eight feet thick.(endnote 12)

Techniques used by Muslim masons and engineers reached great heights of ingenuity. On the river Turia, still in Spain, as an instance, modern measurements have shown that the eight canals have between them a total capacity slightly less than that of the river, thus raising the possibility that the Muslims were able to gauge a river and then design their dams and canals to match.(endnote 13) Smith elaborates on such skills.(endnote 14) Muslim engineers used sophisticated land surveying methods to locate their dams in the most suitable sites, and also to lay out very complex canal systems. For such, they used astrolabes and also trigonometric calculations.(endnote 15)

Around Baghdad water was diverted into the Nahwran Canal which supplied water for irrigation, whilst improvements were made to existing, old systems.(endnote 16) Dams were built of carefully cut stone blocks, joined together by iron dowels, whilst the holes in which the dowels fitted were filled by pouring in molten lead.(endnote 17) An impressive structure of masonry is Hill's impression of the dam at Marib in Yemen, with its carefully cut and fitted blocks using lead dowels in their joints.(endnote 18) It was also fourteen metres high and 600 metres long, with elaborate waterworks including sluices, spillways, a settling tank and distribution tank. So strong a structure, it survived for about ten centuries until lack of financial and technical means made it impossible to maintain.(endnote 19)

Back in Spain, according to Scott, the masonry of the reservoirs was of the finest description, and the cement used was harder than stone itself.(endnote 20) Contingencies were provided for in such manner that no overflow occurred, and no damage resulted even during the worst flooding. Evidence of Muslim engineering `genius' is the fact that these dams needed hardly any repair in a thousand years.(endnote 21) The eight dams on the Turia River at first sight seem to have an exaggerated amount of weight placed on their foundations, the masonry of each dam going some fifteen feet into the river bed, and further support provided by the addition of rows of wooden piles. Such solid foundations were justified by the river's erratic behaviour, which in times of flooding reaches a flow that is a hundred time greater than normal, the structure having to resist the battering of water, stones, rocks and trees.(endnote 22) These dams, now over ten century old, still continue to meet the irrigation needs of Valencia, requiring no addition to the system.(endnote 23)

On the River Segura, the Muslims built a dam in order to irrigate vast lands in the Murcia region.(endnote 24) Because of the nature of the terrain, not just the location, but the design and construction had to be absolutely perfect, too. The height of the dam was only 25 feet, yet its base thickness was 150 and l25 feet, which may seem excessive. Such thickness was necessary to meet the softness and weakness of the river's bed to prevent it from sliding along. The water flowing over the crest initially fell vertically through a height of 13-17 feet on to a level platform, running the length of the dam. This served to dissipate the energy of the water spilling over the crest. The over-flow then ran to the foot of the dam over flat or gently sloping sections of the face. In this way the whole dam acted as a spillway and the energy gained by the water in falling 25 feet was dissipated en route. Thus the risk of undermining the downstream foundations was greatly reduced. Like with other dams, rubble masonry and mortar were used for the interior, and the whole was finished with large masonry blocks.(endnote 25)

The Destruction of Muslim Dams

Like with much else regarding Islamic civilization, once the transfer was accomplished, destruction followed. Muslim dams did not escape in their vast majority the onslaught against Islam. In 1220, the armies of Jenghis Khan devastated the whole eastern parts of the Muslim land. The destruction of al-Jurjaniyah dam south of the Aral Sea diverted the River Oxus from its course and deprived the Aral Sea of water, causing it to nearly dry out centuries later.(endnote 51) A hundred and sixty three years later, in 1383, it was Timur's hordes, which this time completed the work of their predecessors. The Tartars laid the land waste, Zaranj the capital of the province of Seistan, suffering terrible fate; its dams and all its irrigation works completely laid waste. A similar fate befell the Band-I-Rustam, and the region of Bust.(endnote 52) Today, hardly anything survives in those lands once the seats of great civil engineering accomplishments.

by: FSTC Limited, Sun 30 December, 2001

Dam and Water Management

Water Management and Hydraulic Technology

Summarised extracts from a full article, see resources below, where end notes, references and bibliography are given.
by: Foundation for Science Technology and Civilisation. Info@fstc.co.uk
Reservoirs

By far, the most original Muslim reservoirs are to be found in tmhe region of Qayrawan in Tunisia. A lengthy (about 270 pages) account of such structures is offered by the French Solignac.(endnote 26) These reservoirs, possibly for their high aesthetics, and like many other Islamic achievements,(endnote 27) were attributed, despite all evidence,(endnote 28) to both Phoenicians(endnote 29) and Romans.(endnote 30) Such erroneous views were adopted by a number of scholars until modern archaeological excavations and advanced studies proved the Islamic origin of such structures. These reservoirs have two basins, one used for decantation, one as a reserve, and at times a third one for drawing water out of it. Other than their impressive numbers, over two hundred and fifty in the region, such reservoirs also offer a great attraction in their form and structure.

The photograph of the `Basin des Aghlabides,' built in the ninth century by Abu Ibrahim Ahmed reveals, indeed, a sort of temple of water, it is hoped, still preserved in its majesty.

Water Management

Water management in all its intricacies, from Andalusia to Afghanistan, Bolens reminds, was the basis of agriculture, and source of all life. All the Kitab al-Filahat (books of agriculture), whatever their origin, Maghribian, Andalusian; Egyptian, Iraqi; Persian or Yemenite, insist, and meticulously, on the deployment of equipment and on the control of water.(endnote 31) The authorities of the time played a crucial role in that, too. In Iraq, as a rule, hydraulic tasks of a vast nature were left to the state, while the local population focussed its efforts on lesser ones.(endnote 32)

In Egypt, a more elaborate picture comes out.(endnote 33) There, indeed, the management of The Nile waters was most crucial to every single aspect of life, and dams responded to such necessity. Both al-Nuwayri(endnote 34) and al-Makrizi(endnote 35) stressed the role of maintenance of dams and waterways of the Nile for maximum benefits. It was the responsibility for both sultans and holders of large holdings, under both Ayyubids and Mamelouks, to dig and clean canals and maintain dams. As in Iraq the sultan took over the larger structures, and the people the lesser ones. Most distinguished Amirs and officials were also made chief supervisors of such works.(endnote 36) Under the Mamluks there was even an officer for the inspection of dams for each province of Egypt: the Kashif al-Djusur.(endnote 37)

Water Storage

Dams are used to store water, and this has major implications on economic and social life. Smith observes that `not only do dams represent some of the most impressive achievements of engineers over the centuries, but their vital role in supplying water to towns and cities, irrigating dry lands, providing a source of power and controlling floods is more than sufficient to rank dam building amongst the most essential aspects of man's attempt to harness, control and improve his environment.(endnote 38) Effective storage and use of water for irrigation, for instance, can have dramat ic repercussions, in cheapening the process and bringing into use lands that were hitherto impossible or uneconomic to irrigate.(endnote 39)

Both Spain and Sicily offer good illustrations of that. Water is also stored for the aim of providing power for milling. In Khuzistan, at the Pul-I-Bulaiti dam on the Ab-i-Gargar, the mills were installed in tunnels cut through the rock at each side of the channel, constituting one of the earliest examples of hydro-power dams, and not the only one in the Muslim world.(endnote 40) Another example is the bridge-dam at Dizful, which was used to provide power to operate a noria that was fifty cubits in diameter, which supplied all the houses of the town.(endnote 41) Many such hydraulic works can still be seen today.(endnote 42)

Transfer of Hydraulic Technology to Europe

The Islamic mastery of hydraulic technology is far more advanced than acknowledged by some of the sources many writers are too keen to follow. Some references are keen to distort the exact role of Muslim engineering skills. Indeed, to the likes of Gimpel(endnote 43) and White,(endnote 44) the Muslims hardly made any contributions in such a field. Reality, however, is far the opposite. First and foremost, the hydraulic works of the Ancients were found by the Muslims in a terrible state of decay and ruin,(endnote 45) and they did not just repair them, but also added considerable skills of their own. To Spain, for instance, the Muslims brought irrigation techniques which not only laid the foundations for the prosperity of the country, but also with nothing as elaborate and as efficient seen before in Europe.(endnote 46)

After the country was retaken by Christian forces, the Muslims, masters of great skills then, were allowed to retain their functions and serve the new crown. Alongside builders, paper and textile makers, manufacturers of iron and experts of all sorts, the Spaniards also retained and used Muslim irrigation works, their attendant rules and even regulations.(endnote 47) And as soon as the Muslims, who refusing to be baptized as Christians were expelled, or massacred, economic ruin, and famine always followed.(endnote 48) And Spain never recovered its former prosperity and levels of advancement once the Muslims had been eliminated from its land. Hill also notes that the introduction of desilting sluices, the arch dam, and hydropower made their first appearances in the Islamic world, observing that it is `difficult to see how these can be other than Muslim inventions.'(endnote 49)

Further illustration of Islamic impact in the field is not just obvious through the works of Hill, Pacey, Smith and others, it is also visible via the works of Muslim engineers themselves as can still be observed through the remains of old age storage structures all over the Islamic land. Furthermore, White's, Gimpel's and their followers' argument lacks historical backing, for the major changes that took place in Europe, and not just in terms of hydraulic technology, but all others,(endnote 50) did, and without one single exception, at the time the Europeans came into contact with the flourishing Islamic civilisation (twelfth-thirteenth centuries), and not the centuries before. Also, the fact that Western technology in nearly every respect is identical to the Islamic one offers further evidence of such impact.

by: FSTC Limited, Sun 30 December, 2001

Water Management

Water management in Valencia

Quoted from T. Glick in Islamic and Christian Spain in the early Middle Ages, Princeton University Press, New Jersey, 1979. pp 71-3.

The distribution of water among the eight canals of the Valencian huerta is a particularly useful example of [water management] because the underlying principles of the distribution arrangements are well documented and quite easily associated with a specific Islamic model.

The river, now called by its Roman name the Turia, but in Islamic times known as the Wâd al-Abyad (Guadalaviar, "White River"), was considered to be divided into successive stages, each stage representing the point of derivation of one main canal which drew all the water at that stage, or of two canals, dividing the water among them. At each stage the river was considered to hold twenty-four units of water.

The twelve-base system… is standard in many areas of the Islamic world and is clearly related to the hours of the day. A paradigmatic system, so structured, would envision a river divided into 168 units (representing seven days and nights, or 144 if a day of rest was customary). The units were not, however, expressed in hours, but as simple proportions of a whole.

Thus, in times of abundance, each canal drew water from the river according to the capacity of the canal; in times of drought, the canals would take water in turn, for a commensurate number of hours or a proportional equivalent.

The same was true of individual irrigators (and herein lies the genius of the Valencia system): when the canal ran full, each irrigator could open his gate as he pleased, but when water was scarce, a turn was instituted; each irrigator, in turn, drew enough water to serve his needs (this style of irrigation was by submersion of the field, typically to a standard depth of an ankle). But he could not draw water again until every other irrigator in the system had his turn. Thus a relatively equal distribution was ensured, both in times of abundance and of scarcity, and no measurements of time or orifice of delivery were needed.

by: Quoted from T. Glick, Sun 21 July, 2002

Control Engineering

A review of Early Muslim Control Engineering
Summarised extracts from a full article, see resources below, where end notes, references and bibliography are given.

Professor Dr Mohamed MansourEmeritus Professor of Control Eng.ETH Zürich, Switzerlandmailto:info@fstc.co.uk

During the period of Islamic-Arabic extraordinary activity in Science and Technology (9th-13th century) there are some recorded contributions to the area of Automatic Control mainly in the development of water clocks using float valve regulators, different level controls using float valves or combination of syphons and the development of On-Off control.

The Islamic Arabic Automatic Control Technology had as a basis the Greek Technology of two scientists namely Philon of Byzantium (Rhodes and Alexandria) of the second half of the third century BC (his book "pneumatica" was translated from Arabic into French and German in 1902 and 1899 respectively) and Heron of Alexandria of the first century AD (his book "pneumatica" was translated from Greek into English and German in 1851 and 1899 respectively).

It is noted in Greek technology the language is Greek but the scientists need not be Greek as in the case with Islamic-Arabic technology.

It is known that there are hundreds of thousands of manuscripts dealing with Islamic Science and Technology to be edited and it is assumed that some of them deal with technology. This report is based on references [1-6] (see resources below).
PART I - AUTOMATIC CONTROL IN WATER CLOCKS

1. "The work of Archimedes on the Building of Clocks"
This is an Arabic book whose arabic author is called pseudo-Archimedes with the earliest reference to it in "The Fihrist "of Al-Nadim (died 955 AD). From the literary style and the technique of its drawings this clock book seems to be an Islamic work based on Greek-Roman technology as mentioned ini. This clock used a float level regulator, which makes it a feedback device. A large float drove the whole apparatus. The description of the complicated clock is so thorough that it could be reconstructed almost completely. This book did have considerable influence on the two great horological books of Al-Jazari and Ibn Al-Saati and other Arabic authors like Ibn Al-Akfani.

2. "Al-Jami bain Al-Ilm..." by Al-Jazari [5]
This book was written in 1206.Al-Jazari is from Al-Jazira the area between Tigris and Euphrates. Sarton [6] mentions "This treatise is the most elaborate of its kind and may be considered the climax of this line of Muslim achievement "The distinctive feature of the book is its practical aspect. The book is rich in minute discription of various kinds of devices.
Hill [3] maintains "It is impossible to over-emphasize the importance of Al-Jazari`s work in the history of engineering. Until modern times there is no other document from any cultural area that provides a comparable wealth of instructions for the design, manufacture and assembly of machines" "Al-Jazari did not only assimilate the techniques of his non-Arab and Arab predecessors, he was also creative. He added several mechanical and hydraulic devices. The impact of these inventions can be seen in the later designing of steam engines and internal combustion engines, paving the way for automatic control and other modern machinery. The impact of Al-Jazari`s inventions is still felt in modern contemporary mechanical engineering." Hill [4] translated the book to English in 1974. A German translation was made in 1915.The chapter on water clocks describes 10 water clocks, the first two of them use float valve regulators. The various time-indicating mechanisms are propelled by a float. The other clocks are regulated differently. Al-Jazari mentions an old machine, which he inspected, in which a musical automaton was powered by a vertical water wheel. In his comments on this machine he clearly implies that he knew how to control the speed of such a wheel by means of an escapement.

3. "Book on the Construction of Clocks and their Use", Ridwan b.Muhammad Al-Saati Al-Khurasani (1203)
This book describes the monumental water clock built by Ridwan`s father at the Jayrun gate in Damascus. A German translation was made in 1915. A large float drives the clock, float valve regulator and the device for varying the length of the hours are incorporated.

4. "The Book of Secrets about the Resulte of Thoughts", Al-Muradi of Andalusia(11th century) This is the earliest description in Arabic of water clocks. This book deals with water clocks and other devices using automata. The treatise consists of 31 models of which 5 are essentially very large toys similar to clocks in that automata are caused to move at intervals, but without precise timing. The prime movers are water wheels that can be overshot or undershot depending on the intensity of flow. There are nineteen clocks, all of which record the passage of the temporal hours by the movements of automata. The power came from large outflow clepsydras provided with concentric siphons. This power was transmitted to automata by very sophisticated mechanisms, which included segmental and epicyclic gears and the use of mercury. These are highly significant features; they provide the first known examples of complex gearing used to transmit high torque while the adoption of mercury reappears in European clocks from the thirteenth century onwards. Unfortunately, the only known manuscript of this work is badly defaced and it is not possible to understand exactly how the clocks worked. A weight driven clock with a mercury escapement appears in "Libros del Saber" a work written in Spanish at the court of Alfonsos of Castille about 1277 and consisting of translations and paraphrases of Arabic works A novel feature in this treatise is the use of mercury in balances. Al-Zarquali built two large water clocks on the banks of the river Tagus at Toledo in 11th centuryii.

5. "Kitab Mizan Al-Hikma (The Book on the Balance of Wisdom)", Al-Khazini (1121-1122) [2]
The eighth treatise of this work described two steelyard clebsydras. The main one, called the Universal Balance, was designed for 24-hour operation, and consisted of an iron beam divided into unequal arms by a fulcrum. An outflow clepsydra equipped with a syphon was suspended on the end of the short arm, and two movable weights, one large and one small, were suspended from the long arm, which was graduated into scales. As water discharged from the clepsydra, the weights were moved along the scale to keep the beam in balance. At any moment the hour of the day could be told from the position of the large weight, its minutes from the position of the small one."

Part II - Automatic Control of Banu Musa

"Kitab Al-Hiyal" (The Book of Ingenious Devices) by Banu Musa bin Shakir (9th century). The three sons of Musa organized translation and did original work in "Bayt Al-Hikma"(House of Wisdom) which is the science academy in Baghdad the greatest scientific institution since the Museum and Library of Alexandria. Banu Musa were the main supporters of the translation movement which gathered momentum as that important epoch of the Islamic scientific awakening reached fruition in the 9th century. They extended their patronage to Thabit Ibn Qurra, to Hunain Ibn Ishaq and to many other translators and scholars. They have more than 20 works which are known including the seminal engineering book "Kitab Al-Hiyal" translated into English by Donald Hill in 1979 and parts of it into German by Wiedemann and Hauser in 1918 and Hauser in 1922.The book was edited in Arabic by Ahmad Al-Hassan in 1981.

The written Arabic heritage in mechanical technology begins with the Banu Musa book. It is possible they knew Hero`s mechanics written in Alexandria in the first century and translated by Qusta Ibn Luqa at the time of Banu Musa.Hero's other books may have been known to the brothers for he enjoyed great fame among Arabic scholars in the 10th century. Banu Musa describe hundred ingenious devices. Hill identified twenty five devices resembling the ones of Hero and Philo(3rd century BC)books. There exist also other parts of the Banu Musa machines which resemble certain elements in Hero and Philo work. There are Banu Musa machines which bear no resemblance to either Hero or Philo. These include the fountains and dredging machine designed to salvage submerged objects from the bottom of rivers and seas and so on. Banu Musa made use primarily of the principles of the science of hydrostatics and aerostatics. Banu Musa use of automatic valves, delayed-action systems and their application of the principles of automatic control testify of creative mentality. Hill notes the use of crankshafts for the first time in the history of technology.

In two models, they used a mechanism similar to the modern crankshaft, thus outstripping by 500 years the first description of the crankshaft in Europe. Mayr [1] mentions that they use syphons, float valves, Philon`s oil lamp, water wheels, etc. Some control systems work with nonmoving parts combining the principle of Philon`s oil lamp with some cleverly arranged syphons. They have contributions in technological refinements and new applications. They install throttling valves directly in the pipe requiring no constant force to keep them closed. These appear first in the book of Banu Musa. Also they introduce improvements on Philon`s oil lamp by ingenious combination of syphons added to the original system. Most important is the use of On-Off control with upper and lower limit for the controlled variable. Systems of this class are widely used in modern technology. The float valve used by Banu Musa, Al-Jazari and other Arabic engineers emerges again in the middle of the 18th century in Europe and in England.

by: Professor Dr Mohamed Mansour, Fri 22 March, 2002

Control Engineering

Pioneers of Automatic Control Systems

The theory of automatic control systems is an idea closely related to feedback concept. A system is a combination of components that act together and perform certain objectives. In a feedback system the output signal is fed back in order to increase or reduce the input signal.
Although the feedback concept, which is lying in the foundation of dynamic systems, has been perceived relative recently (at the end of the 19th century), it is known that the idea has been understood and applied correctly since the ancient times. In the engineering, the aim of control is to guide the system to a desired direction or kept constant at a certain value. A feedback control system is one which tends to maintain a prescribed relationship between the output and the reference input by comparing these and using the difference as the means of control. Thus, in an automatic control system, the variable to be controlled is first measured, secondly compared against a reference value and at least the difference applied to the system input, in order to influence the system in a desired manner. In the block diagram of an automatic control system, the controlled system take place in the forward path and the measuring device of the controlled variable take place in the feedback loop. A disturbance is a signal that tends to affect adversely the value of the output of a system.
To differentiate an automatic control system, realized and used unconsciously during centuries from the open loop control system, one has to check the existing system for the feedback characteristic. The oldest automatic control systems technically mindfully designed and tested for their operational merit, date back to the Hellenistic era. The oldest applications are flow rate control in water clocks.
Scientific advancement, which reached its peak in the Hellenistic age, lost its luster in the palaces of Byzantium; the Abbasid Caliphs in Baghdad once more let lit the science torch. Muhammad, Hassan and Ahmad known as Benu Musa or Sons of Musa bin Shakir of Khurasan, are very famous in the history of technology. They played an important role in the advancement of mathematical sciences during the reign of Abbasid caliph al-Ma'mun (813-833 A.D) and the succeeding caliphs. Ahmad's interest in technology might have led them to write the book titled Kitab al Hiyal (Book of Mechanical Devices) (850 A.D). The manuscript in the Ahmed III Library at Topkapi Palace is almost a complete copy (A 3474) and includes magical vessels, water jets, o il lamps, a densimeter, a bellow, and a lifting device. This science of 'ingenious devices' and 'ingenious automata' created by the use of matter, water and air is known as 'ilm al-alat al ruhaniyet': science of pneumatic devices. According to Akfani, "the science of pneumatic devices deals with the construction of various devices based on the principle of the 'horror of vacuum'. The purpose is to educate the mind while designing these systems that deal with measured cups, siphons and other elements."
Kitab al Hiyal of Benu Musa brothers describes 100 systems of which 18 are automatic control systems. On close inspection, these control systems are technically perfect and applicable to modern use.

Ancient Egyptian water clocks continuously improved during the ancient Classical period reached monumental dimensions in the Hellenistic period. This tradition continued into the period of Islam and reached its height with al-Jazari, who introduces himself in his manuscript as Badi'al- Zaman abu al-'Izz Ismail al-Razzaz al-Jazarî. He served in the Artukid capital Amid (Diyarbakir) as court engineer. He is famous for his book Kitab al-Hiyal, 'Book of Ingenious Devices' where he explain the design, construction and working principles of fifty different systems of practical use and aesthetic value such as water clocks, automata, water jets, vessels for blood collecting, water raising devices and ciphered keys. In the foreword of his manuscript, he mentions that he served the Artukid rulers Sultan Nasir al-Din Mahmud (1200-1222). For twenty-five years he had been in the service of the royal family, served first for the father of the king Nur al-Din Muhammed (1174-1185) and then for the brother Kutb al-Din Sokman II (1186-1199). He completed his book in 1206. Today, Ahmed III Library at Topkapi Palace houses a second-hand copy of the original manuscript (A 3472). In six sections, the book describes fifty different systems.

Taqi al-Din (1521-1585) was a brilliant engineer and astronomer. He built the Istanbul observatory during the reign of Murad III (1564-1595), and wrote numerous books mainly on astronomy and mechanics. His work on the construction of mechanical clocks is a testimony to competition with the West. When in 1583 the Sultan has ordered the destruction of the observatory, the last research centre of the East closed for more then 200 years.

Figure Sources: Figure (front). An example of a level control from Benu Musa's book titled Kitab al-Hiyal. Donald R. Hill, the Book of Ingenious Devices (Kitab al-Hiyal) by the Band (sons of) Musa bin Shakir, D. Reidel, Dordrecht-Boston, 1979.Figure (top). Rear view of the water clock mechanism. Kitab al-Hiyal, al-Jazari, Topkapi Palace Library, A 3472, fol.18b. Figure (bottom). Front view of the regulator disc with zodiac signs, the marker and the outflow end of the pipe. Kitab al-Hiyal, al-Jazari, Topkapi Palace Library, A 3472, fol. 8a.
by: FSTC Limited, Fri 22 December, 2006

Engineering Inventors

The Machines of Al-Jazari and Taqi Al-Din




This article is based on a paper presented by the Professor Salim Al Hassani at the 22nd Annual Conference on the History of Arabic Sciences, Aleppo, and 23-25 October 2001. It summarises the results of three recent investigations on the Machines of Al-Jazari and Taqi Al-Din, sponsored by the Foundation for Science, Technology and Civilisation (FSTC) and carried out at the University of Manchester Institute of Science and Technology (UMIST) as Final Year student projects for the award of B.Eng Hons. Degree in Mechanical Engineering.


These investigations explore the origin and genius of the inventors and their inventions, (Water Raising Machines and Water Clocks) with in-depth research and discussion from the evolution of the inventions to the rudimentary components used.

Geometrical and mechanical details were obtained from the Arabic original manuscripts and from English translations. Mathematical descriptions of the working (kinetic, motion and energy characteristics) were coded in MATHCAD to predict the various positions of the parts and the motion of the water. The mathematical analysis confirmed the viability and efficiency of the original design as described by Al-Jazari and Taqi Al-Din.

The original dimensions of the components were used to produce modern engineering drawings and these were used to produce images in 3D Studio Max software for each object. After assembling the objects a full three dimensional image is produced of the machine.



The images can be rotated to produce the effect of a fly over and around the machines. By incrementally adjusting the position, according to the machine kinematics of each component, a sequence of images was obtained to produce the effect of 3D animated motion. A CD with full interactive instructions to assist in understanding and investigating the mechanisms of the machines has been produced. This project, for the first time, succeeded in combining state-of-the-art Engineering and Information Technology to bring life to these machines.



Muslim Contributions to Engineering



Studies made during the past fifty years demonstrate that the Muslims made substantial contributions to developments in engineering and that some of their accomplishments were passed on to the Europeans through Spain, Italy and the Crusades.
Many of the achievements made in engineering and technology in the Islamic world in earlier centuries are not well known. Two main reasons for this were suggested by Ludlow and Bahrani [1]:
1. During that period, engineers and technologists were practical rather than literary people. They carried out their work competently but did not write down or publish their discoveries and achievements. Their skills and knowledge were passed on from master to pupil without being recorded. The extent of their ability and skill can now be judged from the few articles and instruments they made which still survive in some museums.
2. In the few cases where the engineers and technologists did write down an account of their work and observations, their manuscripts have been mislaid or destroyed.

During the past fifty years there has been a revival of interest in the history of technology during the early Islamic period. A few Arabic manuscripts dealing with mechanical engineering have been found and some of these were translated into European languages. Among the most important of these manuscripts are:
a. Book of Artifices by Banu Musa (The three sons of Musa Ibn Shakir). This manuscript, which was written in Baghdad about 830 CE, describes approximately one hundred pieces of technical equipment. The book has not yet been properly translated into English.
b. The Book of Knowledge of Ingenious Mechanical Devices by Ibn-al-Razzaz Al-Jazari written in Diyar Bakr (Turkey) about 1206 CE. This book, which has recently been translated into English by Donald R Hill[2] contains descriptions and illustrations of clocks, fountains and perpetual flutes, machines for raising water and a miscellany of other devices.
c. Sublime Methods of Spiritual Machines by Taqi Al-Din, written in Damascus about 1551 CE. This manuscript, which is not yet translated into English, contains descriptions and illustrations of clocks, weightlifting equipment, pumps and various other machines.

The contributions of Engineering in the Islamic world are evidently many yet the materials or treatises available to researchers are very limited, and much more effort is needed to study this field. Useful contributions have been made by Eilhard Widemann, Fritz Hauser, Ahmed Y Al-Hassan and Donald Hill. The latter is the most important contributor to this project and most of his works focus on Al-Jazari's "fi ma 'rifat al-hiyal al-handasiyyah" (The Book of Knowledge of Ingenious Mechanical Devices).
Quoting Dr Donald Hill:
"as far as I am aware, there has been no archaeological study of medieval Islamic technology, nor any detailed technical examination of those machines, which still exist, such as the Noria at Hamah, Syria."
Medieval Islamic technology can be divided into two categories; namely "fine technology" and "utilitarian technology".



The term "fine technology" refers to machines or instruments that were designed to cause wonder and aesthetic pleasure to courtly circles, or for timekeeping, or for the use of scientists (mainly astronomers). The source of information on fine technology can be found in a few previous technical treatises, such as Al-Jazari's "The Book of Knowledge of Ingenious Mechanical Devices".


The term "utilitarian technology" refers to machines that were essential to the economic prosperity of society but were very much simpler technically than the construction of fine technology. The source of information on utilitarian technology comes largely from archaeology finds, examination of existing machines and references in the works of geographers, travellers and other non-technical writers. Machines of this category include mills, water-raising devices and textile machinery[3] .


It is interesting to note that Al-Jazari's Third Water-Raising Device incorporates the two categories of technology together, as the machine is designed to be a beautiful ornamental artefact with splendid craftsmanship, and raises water at the same time.


Al-Jazari
Al-Jazari was in the service of Nasir Al-Din, the Artuqid King of Diyar Bakr, and he spent twenty-five years with the family, having served the father and brother of Nasir Al-Din. The Artuqids were a Turcoman Dynasty who maintained a precarious autonomy during the twelfth century in Mesopotamia[4]. He received patronage from the Artudqid Kings and financial means were provided through salary and pension. Therefore, he was able to devote all his time to study, research, writing and inventions[5]. Al-Jazari was quite evidently a master craftsman himself[6] and regarded himself as one person in a succession of craftsmen and engineers. He states this point, by describing in scrupulous detail how each device was constructed, and much of the language that he used, which involved terms common amongst the craftsmen of that time, are in use right up to the present day. Furthermore, he expressed awareness of the need to develop machines with a better design and greater output than the traditional ones. He did not like to copy his predecessors' work blindly. Rather he was concerned only with innovative and ingenious designs and inventions. Al-Jazari's main virtues were the ability to carefully manufacture and assemble components, and to devise real improvements on the work of his predecessors. He did however have a tendency to be inconsistent in his dimensions, some vagueness about the positioning of the equipment, and failed to give a coherent record of mathematical or geometrical processes.


Taqi Al-Din
Taqi Al-Din was born in Damascus in 1525/6 CE. He died in 1585 in Turkey. His full name was Taqi Al-Din Mohammad bin Ma'aroof bin Ahmad bin Mohammad bin Mohammad bin Ahmad bin Yousef bin Mohammad Al-Shami. He was the son of a judge and he became a judge himself. He was described by his contemporaries as the greatest Scientist / Engineer on earth. He is known to have written 19 books. For details see the book by Prof. A Y Al-Hassan[7]. The machines we modelled are described in his book "al-toruq al-saniyah fi al-alat al-rohanyah".
Much the same observations can be made about Taqi Al-Din as those made for Al- Jazari. Nevertheless, taking drawings and text together, it can be said that they fulfilled their declared intention of describing the devices so that they could be reconstructed by their successors. Indeed, the "castle" water clock was reconstructed in the Science Museum, London, for the 1976 World of Islam Festival. It works perfectly, exactly in accordance with Al-Jazari's intention. Recently the Frankfurt Institute of Arab and Islamic History, under the direction of Professor Fuat Sezgin, has constructed small models of a few of Al-Jazari's devices. Our present project also fulfils that aspiration in that all of Al-Jazari's machines as well as those of Taqi Al-Din will be re-constructed by engineering and computer graphics.


THE WORKING PRINCIPLES OF THE MACHINES



Fig. 1 The reciprocating pump from Al-Jazari's manuscript



(i) The Reciprocating Pump of Al-Jazari
This pump, see Fig. 1, was first made by Al-Jazari in 1206. Taqi Al-Din, 1551, also gave a full description of this pump (see Fig. 2) shows a 3D image of this pump as produced from engineering analysis of the details given by Al-Jazari.
The pump consists of two opposing copper cylinders each containing a piston. The two pistons are connected through a rod which is pin jointed to a swinging arm pivoted at the base of the pump. The arm is slotted so that a crank pin on a gear wheel causes it to swing with wheel rotation. The wheel is driven by a water wheel or an animal drive. The two cylinders are connected to manifolds with inlet and outlet flap. The flaps act as no return valves.



Fig. 2 3D Image of the reciprocating pump with a water wheel as the drive source




Fig. 3 The six cylinder water pump from Taqi Al-Din's manuscript

(ii) The Six Cylinder Pump of Taqi Al-Din
Taqi Al-Din explained how the pump works in his manuscript, see Fig. 3. The input power source is the river and the resultant output is the delivered water head. The river exerts a force on the scoops, which provides the drag force causing the wheel and camshaft to rotate. With rotation of the camshaft, each cam pushes its connecting rod downwards. The connecting rods are pivoted at the centre. The distal end of the connecting rod lifts the lead weight upwards. As the lead weight moves upwards, it pulls the piston with it, creating vacuum which sucks the water through a non return clack valve into the piston cylinder. After the camshaft rotates a certain angle the cam releases the connecting rod. This marks the point where the piston's stroke ends. Thence, the lead weight pushes the piston under gravity forcing against the clack valve. As mentioned earlier, the clack valve closes when the water moves in this direction, so the water is forced to go through the other hole and through the delivery pipes. The synchronisation and control sequence of all the pistons is provided by the angular arrangement of the cams around the shaft.



Fig. 4 3D image of the six cylinder water pump

Fig. 5 The third water raising machine from Al-Jazari's manuscript

(iii) The third water rising machine of Al-Jazari
This machine, See Fig. 5, was described in full by Al-Jazari. Fig. 6 shows a 3D image of this machine. Water flows through the inlet pipe into the basin and out on to the scoops turning the water turbine. The rotation is transferred through the cogwheel (gear A), the Lantern (pinion gear B). The rotation is then transmitted via a pillar connected to the upper Lantern and cogwheel which turn the sindi-wheel. The sindi-wheel carries a series of jars connected to ropes. As the jars dip in and out of the water basin they carry water up to the aqueduct.





Fig. 6 3D image of Al-Jazari's third water raising machine


Fig. 7 The elephant clock from Al-Jazari's manuscript

(iv) The Elephant Clock of Al-Jazari
Fig. 7 shows a sketch of the elephant clock by Al-Jazari. Fig. 8 shows a schematic of the clock as given in foootnote #1. Fig. 9 shows a 3D image of the various components of the clock. The elephant clock is a fine example of the many exquisite devices created during the Muslim Golden Age. It is classified as fine technology as the device is used either for amusement and aesthetic pleasure or for astronomical observation and computation. It is described as one of the most spectacular clocks invented by Al-Jazari and is estimated to be about 4 feet long and 6 feet high. It also demonstrates his considerable skill in both design and construction. The characteristics of the elephant clock consist of several mechanisms that are presently used in modern engineering such as automata, flow regulators and a closed-loop system.
Automata: The clock employed automata, such as striking of the cymbal and chirping of the bird, to mark the passage of the hours.
Flow Regulators: A small orifice in the submersible float is carefully calibrated to produce correct rates of flow under various head of water rates. This rate of flow determines the time at which the clock strikes at hourly interval. It is set by trial and error methods.



Fig. 8 Schematic of the elephant clock

Closed-loop system: The clock will continue to work as long as there are metal balls in the magazine.

Gravitational Force: The clock employs the use of gravitational force as motive power. A submersible float or tarjahar drives it. The steady sinking of the float acts as gravitational force, pulling the wire that activates the tripping mechanism. (a tarjahar is a device used for timing the allocation of irrigation water to farmers). In addition, as the ball drops onto the serpent's mouth (during operation), it activates a gravitational force pulling down the serpent's head. As the ball leaves the serpent's mouth, it activates a return mechanism.
Return Mechanism: The serpent has a return mechanism in the form of a pulley. When the return mechanism is activated, the lowered serpent's head returns to its original position and lifts a chain along with it. This chain is connected to the float and it lifts up the submersible float and empties its content, the submersible float is now on the surface again and the cycle repeats.

Fig. 9 The Mahout on the neck of the elephant, the vases on either side and the scribe on top of the circular platform

Control Mechanisms: The submersible float or tarjahar drives the clock. Initially, the submersible float lies on the surface of the water in the tank. A calibrated orifice on its underside allows water to enter and subsequently sinks the float. Attached to the submersible float are a wire and a chain. The wire runs from the float to the ball release mechanism inside the castle and activates it when the float sinks. The chain runs from the underside of the float to a staple on the tail of the serpent. Upon activation of the return mechanics for the serpent, the chain will tilt the sunken float out of the water thus emptying it of its contents. Then the emptied float will rest on the water surface and repeat the cycle. At the top of the lock, supported by four columns, is the castle (a square brass box with a detachable dome). Inside the castle is a ball release mechanism, which when activated, releases a ball that travels down a channel leading to the beak of the falcon. The ball will travel from the beak of the falcon onto the open mouth of the serpent. The serpent is in effect a pulley which rotates on an axle that rests on bearings fixed between each pair of the columns. Upon loading with the ball, the serpent head will be lowered down to the vase. Once the ball drops away from the serpent's mouth, the return mechanism of the serpent is activated and the serpent returns to its original position.

MATHEMATICAL ANALYSIS

Full mathematical analyses of each machine are contained in the respective project reports placed in the Department of Mechanical Engineering, UMIST, May 2001. It is beyond the scope of this paper to describe these analyses. MATHCAD was used to link up all the equations describing the motion of each component. The dimensions were obtained from Al-Jazari's and Taqi Al-Din's manuscripts. On a number of occasions we had to make a best guess of the actual dimensions of the component.

Essentially, each analysis starts with equating the forces acting on each component allowing for friction as well as compatibility of velocities and displacements and the output is predicted. For example, in the case of Taqi Al-Din's six cylinder pump, the analysis starts with equating the weight of the lead and pistons to the required water head through the collective output pipe. The lead weights are then balanced by the force on the connecting rods which determine the torque on the camshaft which then fixes the force required by the water flow from the river.
Allowance had to be made for friction forces at the pivot and for all sliding surfaces. Further allowances are made for the shape of the scoop at the end of each spoke of the water wheel.
When all the equations are encoded into MATHCAD the solution provides the relationship between the geometrical and mechanical parameters and graphs are plotted to assist in the assessment of the efficiency of the machine. Additional analysis was conducted on the strength requirement of the components. From the forces and torques, stresses were calculated which are compared to the failure strengths and buckling capacity of the components.

3D GRAPHICS AND ANIMATIONS

Modelling and animation were carried out using 3D Studio MAX R3.1 package based on the findings on the research and mathematical analysis of the machines. 3D studio MAX is a very powerful graphics software package used for modelling, animating, image processing and texture mapping for both 2D and 3D objects. Modelling the machines was done in four steps:
1. Creating objects and setting them into positions.
2. Modifying some objects to match those in the real machine.
3. Assigning materials to objects to make them look realistic.
4. Creating lights and cameras and setting them into proper positions to give a real look to the model.

The graphics show the components, devices and machines in different angles of views, close up views and "wire frame" views. The different angles of views include the front perspective view, rear perspective view, front view and left view. The close-up view zooms onto the chambers of the device in perspective view while the "wire frame" view shows the "skeleton" view of the devices. The 3D animations consist of two movie files: a 360o rotational view and one that shows the movements of individual components during their operations. These animations enable the reader to view the device in different angles and also to view the device in operational mode.

The 3D drawing file and animations are stored on CDs to enable a step-by-step construction of the machines or modification of the drawings.
[1] C G Ludlow and A S Bahrani, 1978, Mechanical Engineering during the Early Islamic Period, I. Mech. E, The Chartered Mechanical Engineer, pp 79-83.
[2] Ibn Al-Razzaz Al-Jazari, 1974, The Book of Knowledge of Ingenious Mechanical Devices, translated and annotated by Donald R Hill, Dordrecht, and D. Reidel.
[3] Dionisius A Agius and Richard Hitchcock (Editors), 1994, The Arab Influence in Medieval Europe, Ithaca Press. (p.25)
[4] Donald R Hill, 1998, Studies in Medieval Islamic Technology, Edited by David A King, Ashgate Variorum collected studies series. (p. 253)
[5] Ahmad Y Al-Hassan and Donald R Hill, 1986, Islamic Technology (An Illustrated History), Cambridge University Press. (p.12)
[6] Compilation of writers, 1976, The Genius of Arab Civilisation (Source of Renaissance), Edited by John R Hayes, Oxford, Phaidon. (p.177)
[7] Dr Ahmad Yosuf Al-Hassan, 1999, Taqi Al-Deen wa al-handasah al-meekaneekiyah al-arabiyah (Taqi Al-Deen and the Arabic mechanical engineering) with "Kitab al-toruq al-saniyah fi al-a'alat al-rohaniyah" from the sixteenth century.

by: FSTC Limited, Thu 30 December, 2004

Engineering Inventors

When Ridhwan al-Sa’ati Anteceded Big Ben by More than Six Centuries

A number of attempts were made to explain a device that existed in the past near the Umayyad mosque in Damascus and had functioned for many centuries without much success. Of these are the famous scholarly works of Wiederman [1] and Hill [2]. These considerations drove this author to try to shed some light upon this subject using personal interest, deep understanding of the original manuscripts and hands on experience in reconstructing such clocks.

The device in question is a water clock that alerted hourly beats with loud sound, six centuries before the construction of London's Big Ben in1859.

The clock was placed at the eastern entrance of the Umayyad mosque on the right side of the mosque exit, near the palace of government (Qasr al-Khadhra). The eastern door was named Bab al-sa'at (The Hours Gate). There are other names given to it (e.g., Bab Jayrun and Bab El-Labbadin). The clock was described by one of its early operators, Ridhwan, in a manuscript dated in 600 H/1202 CE. The device was named after him: the clock of Ridhwan al-Sa'ati. It is probably one of the most important mechanical devices in Muslim heritage that used relatively advanced practical technology.

Figure 1. The Umayyad mosque in Damascus. This image has been released into the public domain by its author 'Isaam Bayazidi (at the Arabic Wikipedia project).

This clock demonstrated a great importance of time estimation and consequently earned a prominent location between the government palace and the Umayyad mosque.
Some of its unique features included:
(a) Ability to connect the Hijra calendar for seasons change to the weather,

(b) Define the angle of the sun's rays,

(c) Divide the daytime into 12 equal hours, no matter how much it gets longer or shorter around the whole year,

(d) Alerts the hour by giving a loud sound.

Because of all these features, Ridhwan (as operator of the clock) was awarded a high status as a minister in the government and a special budget was devoted to the device by the government of the time.

Ridhwan's clock belongs to the group of hydraulic timing devices which were well known in the past such as Clepsydra [3] and Ghati [4]. It demonstrates the development that had occurred in clock construction from the time when a water-wooden clock was gifted by Caliph Harun al-Rashid in 170 H/786 CE to Charlemagne I (reigned 768-814 CE). It is believed that different forms of such devices were spread in the Muslim world.

From the manuscript of Ridhwan al-Sa'ati, we find that Abu 'Abdullah Muhammad b. Naser b. Saghir b. Khalid al-Kaysarani, a scholar well versed in poetry, observational astronomy, engineering and mathematics, had started managing and operating the clock before the Sultan Nur Ed-Din Mahmud b. Zanki took over Damascus in the year 549 H/ 1154 CE.

After al-Kaysarani, the father of Ridhwan al-Sa'ati, Muhammad b. 'Ali al-Khurasani, had reconstructed the clock after it had got burned in 562 H/ 1166 CE. Then Ridhwan al-Sa'ati mentions three other people that had operated the clock after his father's death. These were: al-Muhadhab b. al-Naqqash, al-Muhadhab b. al-Hajib and Abu al-Fadhl al-Najjar.
Subsequently, the management of the device was transferred to Ridhwan al-Sa'ati himself. Ridhwan was known as Fakhr al-Din Ridhwan al-Sa'ati al-Khurasani al-Dimashqi. He held a ministerial post in the time of King 'Isa b. al-Malik al-'?del Muhammad who had assigned a special budget to this device.

Figure 2. Overall plan of the Umayyad mosque where the "Dome of the clocks" appears near Bab Jayrun. Sources: Saeed Arida (2003), Aga Khan Program for Islamic Architecture, MIT:

http://archnet.org/library/files/one-file.tcl?file_id=1624 , and http://almashriq.hiof.no/syria/900/910/919/damas/ummayad_mosque/9810/history.html

The clock of Ridhwan [5] is a mechanical device – relatively advanced for its period– that works on water evacuation. It was constructed before it was described in 600 H/1202 CE.
The device was described in three manuscripts. The original (which was dictated by Ridhwan himself) is located now in the the library Forschungsbibliothek in Gotha in Germany. The other one is a copy that was scribed fifty-six years after the original by Baylak 'Abdullah al-Qabagaqi [6], an Egyptian engineer; it is kept in Istanbul. A third manuscript, a copy of that of al-Qabagaqi; it is preserved in Cairo (National Egyptian Library, Taymur Pasha collection, MS 24 Sina'a).

The clock device was described by different travelers. The first of whom was Rabbi Benjamin of Tudela who visited Damascus between 554 and 570 H (159-1174 CE) [7]. His description is as follows:
"Damascus has a Mohammedan synagogue [sic] that is called the synagogue of Damascus; it is unequalled in the world. This must be the palace of Ibn Haddad. One of the walls was built by a magical power and it contains as many openings as the number of days of the solar year. The sun throws its rays in succession in the openings. These are divided into twelve degrees to match the hours of the daytime, from this arrangement one can figure the time [8]."
This description, of a sun clock assumed to be located near the Umayyad mosque, does not match by any means any description of the clock such as those made by Ridhwan himself and by two subsequent travelers, Ibn Jubayr and Ibn Battuta. It is likely that the description made by Rabbi Benjamin was mistakenly taken by Donald R. Hill in his book Arabic Water clocks as that of Ridhwan al-Sa'ati's clock.

Ibn Jubayr had described this water clock in the account he made of his journey and stay in Damascus in the year 580 H/1184 CE. His description is very close to that of Ridhwan al-Sa'ati's manuscript. The account by Ibn Battuta in 726 H/1326 CE is close to Ibn Jubayr's but much more concise.

The survey and the analysis of all the available literature about Ridhwan's clock revealed that the Egyptian engineer 'Abdullah Baylak al-Qabagaqi remains the person who had best understood this water clock because of his direct acquaintance with the device, and also because of a pertinent note which he inserted in his copy of Ridhwan's original manuscript:
"The author of this manuscript (himself) was aware of and an expert in the work of the clock except for al-siniyya [the tray]".

By this pertinent note, he revealed one of the weak points of Ridhwan's work related to the lack of understanding of a special part of the clock called al-siniyya, which is designed for the water exit.

Figure 3. Narrative of the description of the clock by Ibn Jubayr. In: Rihlat Ibn Jubayr, Beirut, 1986, vol. 2, pp. 218-219.

Figure 4. Narrative of Ibn Battuta. In: Rihlat Ibn Battuta. Quoted from the website al-Warraq: http://www.alwaraq.net/index2.htm?i=67&page=1

In the early twentieth century, the German physicist and historian Eilard Wiedemann and Fritz Hauser studied the clock device and reached a high level of understanding of its workings. They published the results of their research in 1915 in several articles. Whilst their work was pioneering, unfortunately they produced an incomplete conception of the device and their explanations contained some errors.

Donald R. Hill discussed the subject of Ridhwan's clock. He relied on the studies of Wiedemann and Hauser on various water clocks, using much of their engineering drawings, albeit without acknowledging them. He then concluded his study by affirming: "All the descriptions written about this instrument aren't sufficient to reconstruct it". It appears that he confused the description of this same clock with that made by Isma'il ibn al-Razaz al-Jazari in his original Arabic manuscript which Hill had edited in the book A Compendium on the Theory and Practice of the Mechanical Arts (completed by al-Jazari in 602 H/1206 CE).

In the year 1926 an educational curriculum, named al-Qira'a al-Rashideh, was adopted in Syria and Egypt. Its first set of lessons was a text of the famous Muslim scholar Imam al-Ghazali (died on 505 H/1111 CE) about the beating water clock which carries the main concept of the clock of Ridhwan al-Sa'ati. An original copy of that educational book is kept in al-Zahiryeh library in Damascus. The present author was fortunate to have had access to it and scrutinized it carefully.

Figure 5. Diagram of Ridhwan al-Sa'ati's clock as depicted in the original manuscript of his book 'Amal al-Sa'at wa 'l-'Amal biha as edited by M. A. Dahman (Damascus, 1981). Reproduced from Jalal Shawqi, Al-'ulum wa 'l-ma'arif al-handasiyya fi al-hadhira al-islimiya (Mechanical Knowledge in Islamic Civlisation), Kuwait: KFAS, 1995, p. 297.

Furthermore, Sheikh Muhammad Ahmad Dahman edited the manuscript of Ridhwan and presented it with an important and learned introduction. He assumed that the manuscript rendered the original text sufficiently clear to assist in the reconstruction of the clock and consequently, did not add any comments to explain its operation and construction [9].

One has to warn, at this juncture, that there are claims that some parties actually reconstructed the clock of Ridhwan al-Sa'ati (the Umayyad mosque clock) and have even placed its pictures on the internet. Such claims have to be challenged through scientific scrutiny and due diligence by returning to the original manuscript and the works and drawings of Wiederman and Hauser, and Donald Hill.

To know this instrument with all its details and to try to reconstruct it, one should possess a detailed knowledge of Arabic mechanical works, including the book of Banu Musa (Baghdad, 3rd century H/9th century CE) Kitab al-hiyal (Book of machines), al-Jazari's long encyclopedia al-Jami' bayn 'l-'ilm wa 'l-'amal fi sina'at al-hiyal (Compendium of the theory and practice of the mechanical arts), the works of Taqi al-Din ibn Ma'ruf and the state of Arab mechanical engineering up till 10th century H/16th century CE.

The present author, with the encouragement of the Foundation for Science, Technology and Civilisation (FSTC, UK), has been able to reconstruct this fascinating and unique clock.
To have such a clock nowadays working, beating and ringing is a gratifying pleasure and a call from the past that fills us with pride and adds magic to the reality. Let us now describe this extraordinary device which was once considered one of the wonders of the Muslim world.

The original device was located on two levels on the right side of the one who leaves the eastern door of Umayyad mosque. The lower level contains the copper water vessel and float device that generates the movement, the upper level contains the mechanical parts that cause and control the activities of the clock.

The upper external part is a large wood and copper board of approximate dimensions (240 x 240 cm) containing the following:
1. Twelve brass doors, each one rotates on the hour to show its back face with the number of the hour that has passed;
2. Below the doors there is an indicator with a meniscus that slides – to show the parts of an hour – beside a ruler scaled into five minute parts;
3. Above each door there is a copper dome, each dome rises after an hour has passed;
4. At the sides of the copper doors two falcons (bazan) throw copper balls into a large copper cup to generate the ringing sound;
5. It has a circular copper plate with the signs of the zodiac inscribed on the circumference to connect the Hijri calendar (lunar calendar) with the solar calendar and also to forecast the annual weather and the change of seasons;
6. An arrow indicates the angle of the sun with respect to the earth during the daytime;
7. There is a semi-circular disc called the night circle that contains 12 circular openings that are lit when the clock turns to show the time at night;
8. The most important function of this clock is that it is called the temporal clock. This is because it divides each daytime whatever its length (a summer day or a winter day) into twelve equal hours and the same for the night hours. Thus, the daytime always remains 12 hours from sunrise to sunset which fixes the times of prayers (the noon prayer is always at 6 o'clock).

The ordinary 24-hour is called the flat clock and resembles our daily clocks (always dividing the day and night together into 24 hours). The Ridhwan temporal clock has the capability of working as flat clock as well. Obviously both clocks would be identical in timing during the spring equinox (21-22 March) and the autumn equinox (21-22 September) when the lengths of the day and the night are equal.

It is perhaps worth commenting that the correct title of the original manuscript of Ridhwan al-Sa'ati is `Amal al-Sa'at wa 'l-`Amal biha not 'Ilm al-Sa'at wa 'l-`Amal biha. The first means "The making of al-sa'at (the clock) and working with it". The second, which is used by all western researchers, means "The science of al-sa'at (the clocks) and working with it". This error unfortunately hides the fact that Ridhwan's manuscript was actually for instructing the operator and not on the science of clocks. Not knowing Arabic and not having hands on experience with water clocks can easily cause misinterpretation. For example, if one analyses the text carefully, one would find that Ridhwan divided the water regulator into 72 parts and not to 360 parts (like in Hill's explanation). One can even identify some other mistakes actually made by Ridhwan himself.

Ridhwan had explained in his manuscript that he wrote the description of al-sa'at to instruct a midi-clever worker on how to make the water clock.
End Notes
[1] Eilhard Weidermann and Fritz Hauser, Uber die Uhren im Bereich der islamischen Kultur. Halle: Karras, 1915.
[2] Donald R. Hill, Arabic Water clocks, Aleppo: Aleppo University, Institute for the History of Arabic Science, 1981.
[3] In the clepsydra, timing is measured by the movement of the water surface as it leaks from a containing vessel that has an orifice at its base.
[4] Timing is measured in this waterclock by the level of an empty open vessel as it sinks due to water leaking into it through an orifice at its base. The device existed mainly in India in the past. [5] It should be noted that the term sa'at is the plural of hour in Arabic. Nowadays, the Arabic term al-sa'ati refers to "watchmaker". The world famous advertising firm "Saachi and Saachi" derives its name from the Iraqi origin of the family named as-Sa'ati. The old Arabic term for clock was minjana or binkam.
[6] This author flourished around 681 H/1282 CE, for amongst his writings Kanz al-Tijjar fi Ma'rifati 'l- Ahjar is dated in this year (681 H/1282 CE). An autograph of this text is kept in the French National Library in Paris (MS arabe 2779). In it he describes the use of magnetic compass by Arab navigators.
[7] D.R. Hill, op. cit.
[8] The Itinerary of Rabbi Benjamin of Tudela, translated by A. von Asher (London, 1841), vol. 1, p.84; quoted in D.R. Hill, Arabic Water Clocks.
[9] Ridhwan b. Muhammad al-Sa'ati, 'Ilm al-Sa'at wa 'l-'Amal biha, edited by Muhammad Ahmad Dahman. Damascus: Maktab al-dirasat al-islamiyya, 1981.
* Abdel Aziz al-Jaraki is an architect in Damascus, and a consultant for Foundation for Science, Technology and Civilisation (FSTC), UK.

by: Abdel Aziz al-Jaraki, Wed 11 April, 2007