Medieval Islam was a prosperous and dynamic civilization, and much of its prosperity was due to an engineering technology that assisted in increasing the production of raw materials and finished products. In addition, the demand for scientific instruments, and the need to cater for the amusements and aesthetic pleasures of the leisured classes, was reflected in a tradition of fine technology based upon delicate and sensitive control mechanisms. This is a very wide subject indeed, and the Islamic contribution to the development of modern engineering will be indicated by means of citing individual cases of technology transfer.
Civil Engineering
Irrigation and Water Supply
With the spread of the Islamic Empire westward, agricultural and irrigation methods and techniques were introduced into the western regions of Islam. The rulers of al-Andalus and many of their followers were of Syrian origin, and the climate, terrain and hydraulic conditions in parts of southern Spain resemble those of Syria. It is hardly surprising, therefore, that the irrigation methods - technical and administrative - in Valencia closely resemble the methods applied in the Ghuta of Damascus.[2]There is a unanimous opinion among historians that the present Spanish irrigation systems of Valencia and Andalusia are of Muslim origin. In 1960 a celebration was held in Valencia commemorating the ‘Millennium of the Waters’. It expressed public recognition of the establishment of the irrigation system, and specifically of the Tribunal of Waters during the reign of 'Abd al-Rahman III'. The irrigation system that had been instituted in the days of the caliphs in Valencia was perpetuated and confirmed under the succeeding dynasties, until, when the Christian conquerors appeared in the thirteenth century, it recommended itself for adoption, backed by the experienced benefits of several centuries. The Arabic names used in the irrigation systems give distinct proofs of the Moorish origin of the irrigation systems in eastern Spain. There is some difference between eastern Spain (Valencia and Murcia) and the kingdom of Granada. The chief object of the Granada water supply system was not the irrigation of crops only but the distribution of water to the fountains and baths of the capital. In Granada the system is still "to an exceptional degree" the same as it was in the time of the Arabs, and we find undisturbed the institutions practiced by the Arabs themselves.
An acequia flowing toward Granada from the spring in the village of Alfucar in the foothills of the Sierra Nevada, was first built in the 13th century and is still flowing today .
The Arabic systems in irrigations were diffused from al-Andalus to Christian Spain. This accounts for the Aragonese traditions of irrigation. These systems of irrigation had migrated from Spain to America where we find them still practiced in San Antonio in Texas. The story begins properly in the Canary Islands where in the late fifteenth century; settlers from Spain introduced Islamic institutions of water distribution. They brought with them to the American southwest both the technology and institutional framework for irrigation and the distribution of water.
The Qanat
The qanat system was an efficient method for irrigation and water supply. It originated in pre-Islamic Iran. The qanat technology spread westward to North Africa, Spain, and Sicily. The Andalusi agronomical writers provide practical advice on well-digging and qanat construction. From Spain the qanat technology was transferred to the New World and qanats have been found in Mexico, Peru, and Chile. In the 1970s a qanat system 2.3 kilometers long was located in the La Venta area, just 10 km northwest of Guadalajara, Mexico. In Palermo, Italy, a qanat system from the Arab days was used to bring fresh water to the city and to irrigate its beautiful gardens. There are current plans to revive and reconstruct the Arabic qanat and utilize it to solve the acute needs of the modern city of Palermo for potable water. The project in hand is of great historical, archaeological, geological and hydro-geological importance. It is already of great interest for tourists.
Dams
There are many Muslim dams in Spain, a large number of which were built during the tenth century AD, the golden age of Umayyad power in the peninsula. In this period, for example, many small dams, or azuds, were built on the 150-mile-long River Turia, which flows into the Mediterranean at Valencia. (In passing it is important to note the Spanish word azud, from Arabic al-sadd, one of many modern irrigation terms taken directly from Arabic and certain proof of Muslim influence on Spanish technology.) Eight of these dams are spread over six miles of river in Valencia, and serve the local irrigation system. Some of the canals carry water much further, particularly to the Valencian rice fields. These, of course, were established by the Muslims, and continue to be one of the most important rice-producing centres in Europe. Because of their safe design and method of construction, and because they were provided with deep and very firm foundations, the Turia dams have been able to survive the dangerous flood conditions for 1000 years.[3]
Mechanical Engineering
Water-Raising Machines
Today, this ancient water raising machine is seen in a few farming areas in the northern Mexican states. It also survives in the Yucatan Peninsula. It is reported that one group of farmers in Veracruz, Mexico is reverting back to using the traditional technology of the saqiya. The na'ura (noria) is also a very significant machine in the history of engineering. It consists of a large wheel made of timber and provided with paddles. The large-scale use of norias was introduced to Spain by Syrian engineers. An installation similar to that at Hama was in operation at Toledo in the twelfth century. The Na'ura (Noria) of Albolafia in Cordoba also known as Kulaib, which stands until now, served to elevate the water of the river until the Palace of the Caliphs. Its construction was commissioned by Abd al-Rahman I, and has been reconstructed several times.
The Noria of Cordoba
The noria was heavily exploited all over Muslim Spain. It was diffused to other parts of Europe, and, like the Saqiya, has shown remarkable powers of survival into modern times. Five water-raising machines are described in al-Jazari's great book on machines, composed in Diyar Bakr in 1206. One of these is a water-driven saqiya, Three of the others are modifications to the shaduf. These are important for the ideas they embody, ideas which are of importance in the development of mechanical engineering as we shall mention below. The fifth machine is the most significant. This is a water-driven twin-cylinder pump. The important features embodied in this pump are the double-acting principle, the conversion of rotary into reciprocating motion, and the use of true suction pipes. The hand-driven pumps of classical and Hellenistic times had vertical cylinders which stood directly in the water which entered them through plate-valves in the bottoms of the cylinders on the suction strokes. The pumps could not, therefore, be positioned above the water level. This pump of al-Jazari could be considered as the origin of the suction pump. The assumption that Taccola (c. 1450) was the first to describe a suction pump is not substantiated. The only explanation for the sudden appearance of the suction pump in the writings of the Renaissance engineers in Europe is that the idea was inherited from Islam whose engineers were familiar with piston pumps for a long time throughout the Middle Ages.
Twin Cylinder Suction Pump of Al-Jazari
Evidence for the continuation of a tradition of mechanical engineering is provided by a book on machines written by Taqi al-Din about the year 1552. A number of machines are described, including a pump similar to al-Jazari's, but the most interesting device is a six-cylinder 'Monobloc' pump. The cylinders are bored in-line in a block of wood which stands in the water - one-way valves admit water into each cylinder on the suction stroke. The delivery pipes, each of which is also provided with a one-way clack-valve, are led out from the side of each cylinder and brought together into a single delivery outlet. It is worthy of note that Taqi al-Din's book antedates the famous book on machines written by Agostino Ramelli in 1588. It is therefore quite possible that there was some Islamic influence on European machine technology even as late as the sixteenth century as we have alluded above.
Power from Water and Wind
The Muslim geographers and travelers leave us in no doubt as to the importance of corn-milling in the Muslim world. This importance is reflected by the widespread occurrence of mills from Iran to the Iberian Peninsula. Arab geographers were rating streams at so much 'mill-power'. Large urban communities were provided with flour by factory milling installations. The ship-mill was one of the methods used to increase the output of mills, taking advantage of the faster current in midstream and avoiding the problems caused by the lowering of the water level in the dry season. Another method was to fix the water-wheels to the piers of bridges in order to utilize the increased flow caused by the partial damming of the river. Dams were also constructed to provide additional power for mills (and water-raising machines) In the twelfth century al-Idrisi described the dam at Cordoba in Spain, in which there were three mill houses each containing four mills. Until quite recently its three mill houses still functioned.
Existing Mill Houses on a Dam Near Cordoba Were Described by al-Idrisi
Evidence of the Muslims' eagerness to harness every available source of water power is provided by their use of tidal mills in the tenth century in the Basra area where there were mills that were operated by the ebb-tide. Tidal mills did not appear in Europe until about a century after this. Water power was also used in Islam for other industrial purposes. In the year 751 the industry of paper-making was established in the city of Samarqand. The paper was made from linen, flax or hemp rags. Soon afterwards paper mills on the pattern of those in Samarqand were erected in Baghdad and spread until they reached Muslim Spain. The raw materials in these mills were prepared by pounding them with water-powered trip-hammers. Writing about the year 1044, al-Biruni tells us that gold ores were pulverized by this method "as is the case in Samarqand with the pounding of flax for paper". Water power was also used in the Muslim world for fulling cloth, sawing timber and processing sugarcane. It is yet to be established to what extent industrial milling in Europe was influenced by Muslim practices. A likely area of transfer is the Iberian Peninsula, where the Christians took over, in working order, many Muslim installations, including the paper mills at Jativa.
Fine Technology
The expression 'fine technology', embraces a whole range of devices and machines, with a multiplicity of purposes: water clocks, fountains, toys and automata and astronomical instruments What they have in common is the considerable degree of engineering skill required for their manufacture, and the use of delicate mechanisms and sensitive control systems. Many of the ideas employed in the construction of ingenious devices were useful in the later development of mechanical technology. The tradition of pre-Islamic fine technology continued uninterrupted under Islam and was developed to a higher degree of sophistication. Monumental water clocks in Syria and Mesopotamia continued to be installed in public places. The Abbasid Caliphs were interested in clocks and ingenious devices. The story of the clock that was presented by Harun al-Rashid (786-809), to Charlemagne in 807 AD is well known.[4]
The Monumental Water Clock of Al-Jazari
The Evolution from Water to Mechanical Clocks
The technology of clock- making was transferred to Muslim Spain. About the year 1050 AD, al-Zarqali constructed a large water clock on the banks of the Tagus at Toledo in Spain. The clock was still in operation when the Christians occupied Toledo in 1085 AD. A manuscript describing Andalusian monumental clocks was written in the eleventh century by Ibn Khalaf al-Muradi. Most of his devices were water clocks, but the first five were large automata machines that incorporated several significant features. Each of them, for example, was driven by a full-size water wheel, a method that was employed in China at the same period to drive a very large monumental water clock. The text mentions both segmental and epicyclical gears. (In segmental gears one of a pair of meshing gear-wheels has teeth on only part of its perimeter; the mechanism permits intermittent transmission of power). The illustrations clearly show gear-trains incorporating both these types of gearing. This is extremely important: we have met simple gears in mills and water-raising machines, but this is the first known case of complex gears used to transmit high torque. It is also the earliest record we have of segmental and epicyclical gears. In Europe, sophisticated gears for transmitting high torque first appeared in the astronomical clock completed by Giovanni de Dondi about AD 1365. In a Spanish work compiled for Alfonso X in 1277 AD, in which all the chapters are translations or paraphrases of earlier Arabic works we find a description of a clock. It consisted of a large drum made of wood tightly assembled and sealed. The interior of the drum was divided into twelve compartments, with small holes between the compartments through which mercury flowed. Enough mercury was enclosed to fill just half the compartments. The drum was mounted on the same axle as a large wheel powered by a weight-drive wound around the wheel. Also on the axle was a pinion with six teeth that meshed with thirty-six oaken teeth on the rim of an astrolabe dial. The mercury drum and the pinion made a complete revolution in 4 hours and the astrolabe dial made a complete revolution in 24 hours. Clocks incorporating this principle are known to work satisfactorily, since many of them were made in Europe in the seventeenth and eighteenth centuries. This type of timepiece, however, with its effective mercury escapement, had been known in Islam since the eleventh century, at least 200 years before the first appearance of weight-driven clocks in the West. An important aspect of Islamic fine technology is the tradition of geared astronomical instruments which were described in Arabic literature. The most notable example is the astronomical geared mechanism that was described by al-Biruni and called by him Huqq al-Qamar (Box of the Moon). From al Biruni's text we understand that these mechanisms were known in Islamic astronomy. A surviving example is the geared calendar dated 1221/2 AD that is part of the collection of the Museum of the History of Science at Oxford. Derek J. de Solla Price[5] when describing the Antikythera mechanism (90 AD) remarked that "It seems likely that the Antikythera tradition was part of a corpus of knowledge that has since been lost but was known to the Arabs. It was developed and transmitted by them to medieval Europe, where it became the foundation for the whole range of subsequent invention in the field of clockwork"
Al-Biruni’s Mechanical Calendar (British Library, MS OR 5593)
Geared Astrolabe-Calendar of Muhammad b. Abi Bakr, 13th Century (Museum of the History of Science, Oxford).
Many of the ideas that were to be embodied in the mechanical clock had been introduced centuries before its invention: complex gear trains, segmental gears in al-Muradi and al-Jazari; epicycle gears in al-Muradi, celestial and biological simulations in the automata-machines and water clocks of Hellenistic and Islamic engineers; weight-drives in Islamic mercury clocks and. pumps, escapements in mercury docks, and other methods of controlling the speeds of water wheels. The heavy floats in water clocks may also be regarded as weights, with the constant-head system as the escapement.The knowledge that Christians in Spain learned about Muslim water clocks was transferred to Europe. Water clocks in Europe became very elaborate with complications that were often a source of fascination and amusement. There are records of an early medieval water clock where figures of angels would appear every hour, bells would ring, horsemen appeared and a little man, known as a jack, would strike the hour bell with a hammer. This is reminiscent of one of al-Jazari's water clocks.
In a treatise written by Robertas Anglicus in 1271, it is mentioned that the clockmakers - i.e. the makers of water clocks - were trying to solve the problem of the mechanical escapement and had almost reached their objective. The first effective escapement appeared a few years later. This evidence, circumstantial though it is, points strongly to an Islamic influence upon the invention of the mechanical clock.
Feedback Control and Automata
Feedback control is an engineering discipline. As such, its progress is closely tied to the practical problems that needed to be solved during any phase of human history. The Book of Ingenious Devices (Kitab al-Hiyal) of Banu Musa, was written in Baghdad about 850. It contains descriptions of a hundred devices, most of which are trick vessels which exhibit a bewildering variety of effects. 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. The means by which these effects were obtained are of great significance for the history of engineering. By the end of the tenth century, the construction of automata was probably a well-established practice in the Arabic world. There is historical evidence that the skills of automata makers were enlisted to add distinctive features to royal palaces.[6] The early history of automata in Europe goes back to Arabic automata in Muslim Spain. We have mentioned how the technology of water clocks had been transferred to Western Europe. The elaborate automata of Islamic water clocks became a feature of European water clocks also. The Banu Musa used conical valves as "in-line" components in flow systems, the first known use of conical valves as automatic controllers. An almost constant head was maintained in a float chamber by feedback control. Other Muslim engineers used the float regulator and the important feedback principle of "on/off control in their water clocks and automata. As mentioned above, water clocks spread in Europe for some time before they were replaced by mechanical clocks, and it follows that European engineers and technicians were acquainted also to the float regulators and the automata that accompanied them. In the late 1700's, regulation of the level of a liquid was needed in two main areas: in the boiler of a steam engine and in domestic water distribution systems. Therefore float regulator devices once again become popular during the Industrial Revolution. The important feedback principle of "on/off control that was used by Muslim engineers came up again also in connection with minimum-time problems in the 1950's.[7]
Astronomical Instruments
The astrolabe was the astronomical instrument par excellence of the Middle Ages; from its Hellenistic origins it was brought to perfection by Muslim scientists and craftsmen. A number of astronomical problems, which otherwise have to be solved by tedious computation, can be solved very quickly by using the astrolabe. It has been established that the first European treatises on the astrolabe were of Arabic inspiration and were written in Latin at the beginning of the eleventh century in the abbey of Ripoll in Catalonia. From this centre the knowledge of the instrument was diffused to the rest of Europe. Other computing instruments were devised in the Muslim world in the later Middle Ages, perhaps the most important of these being equatoria, which were invented in Muslim Spain early in the eleventh century. The objective of the equatorium was the determination of the longitude of any one of the planets at a given time. As with the astrolabe, knowledge of equatoria was diffused into Europe from the Muslim world.
