| Machine | Winter Area | Summer Area |
| Shaduf | 70 | 30 |
| One-Ox Saqiya | 70 | 30 |
| Noria | 350-400 | 80 |
Al-Jazari must also have faced the same problem, thence in order to invent a water-raising device, he also needs to do some research and analytical work so as to incorporate the most suitable mechanisms into his invention. It is interesting to note that indeed some of the mechanisms he used were either of higher efficiency or special characteristic, such as the Scoop-Wheel and Sindi Wheel. These mechanisms will be discussed in detail and arguments will be made as to why he incorporates these mechanisms into this invention.
1. Scoop-Wheel or Water Turbine
The first mechanism to strike by the force of water is the Scoop-Wheel (see Fig. 12) which in turns drives the rest of the mechanisms. This mechanism consists of scoops being fixed to the ends of spokes that radiate from a solid disc [4], and can also be found incorporated in several other devices in al-Jazari's book, such as the water clock of the peacock.
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Figure 12: A 3D graphic of the Overshot Scoop-Wheel. |
The first description of the Scoop-Wheel was by Philo of Byzantium. In his work, he introduce a water-raising device whereby a chain of buckets is driven by an Undershot Wheel with a series of spoon-shaped spokes arranged in a circle around the hub (see Fig. 13). In addition, Philo remarks that the wheel "can be applied to many other uses" [5].
It seems that Al-Jazari might have studied Philo's work [6] and noticed the ingenious Undershot Wheel of unusual design set up to work a string of pots by a chain drive [7]. Later, Al-Jazari improved on its design by converting it from an Undershot Wheel to an Overshot Wheel and later echoed Philo's remark by incorporating the Scoop-Wheel design as part of his striking mechanism in his various devices [8].
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Figure 13: The bucket-chain water hoist powered by an Undershot Scoop-Wheel as described by Philo of Byzantium. |
The Scoop-Wheel was intended for taking energy from water and transmitting it to other mechanisms. It was more commonly employed in the reverse sense, which is imparting the motion of water. In a certain sense, al-Jazari's concept of the Scoop-Wheel is similar to a primitive Pelton wheel (see Fig. 14) which depends on a high head of water for its effectiveness, since there is no utilisation of pressure energy. One important consideration is that the water must be directed accurately into the scoops, which have to have a properly designed profile to obtain a maximum change in momentum of the jet flow [9]. Judging by al-Jazari's serious attitude towards his work, it seems that there is no doubt that he would have carefully calibrated the jet flow accurately on the scoop and that the Scoop-Wheel would power the invention as desired.
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Figure 14: A small low-powered Pelton wheel of the 1890s. |
1.1. How did al-Jazari Invent the Scoop-Wheel Design?
Assuming that al-Jazari was ignorant of Philo's work, as we claimed earlier, then it would be a reasonable assumption that he derived his Scoop-Wheel design from the principle of the Overshot Wheel and the Noria, which had a wheel for lifting water with buckets scoops fixed to its outer rim. However, even though we consider that he had based this design on Philo's work, he must had to rely on the mechanism of Scoop-Wheel to power his invention.
1.2. Why did he Use the Scoop-Wheel Instead of the More Common Overshot Wheel?
The reason is that Al-Jazari was interested only with the innovative and ingenious water wheels, whereas ordinary wheels, such as the Overshot Wheel, were taken for granted and evoked no interest [10]. However, it is interesting to note that according to John Smeaton's experiments, impact between a stream of water and a flat plate resulted in a marked loss of energy in the form of spray and turbulence. Thence leaving us to wonder did al-Jazari know about this or was it by a stroke of luck that he happened to use the curvaceous Scoop-Wheel instead of the flat-plated Overshot Wheel?
1.3. Why did he Convert the Undershot Scoop-Wheel to an Overshot Scoop-Wheel?
As mentioned before, al-Jazari had expressed awareness for the need to develop machines with a better design and greater output than the traditional ones. He might have done experiments on his own and most probably obtained the similar results [11]. Furthermore, his concept of the invention is to hide the lower chamber of the driven mechanism, allowing only the flow of water down, hence the Overshot Wheel design would have been more appropriate in this case.
1.4. Comparison between the Undershot Wheel and the Overshot Wheel?
First of all, we know that both wheels have been around since Vitruvius (100 BCE) who described them in his work [12]. Next, we need to understand the working principles of these two wheels. The Undershot Wheel rotates by the pressure of the moving water, on the paddles of the lower part of the wheel (see Fig. 15). This means that it requires a considerable volume of water with a rapid flow, therefore a wasteful means of using waterpower [13]. Whereas the Overshot Wheel rotates by the pressure of water pouring from above onto the top paddles, thus a small volume of water is sufficient (see Fig. 16).
Finally, we need to know its supply of waterpower. Although the Overshot Wheel is technically more efficient [14], however it needed a constant supply of water from an aqueduct or if fed by sluggish rivers in a flat country demanded the construction of a millrace, a mill-pond and a chute plus sluice for proper manipulation. Whereas the Undershot Wheel, depended on swiftly flowing water and a fairly constant volume of water the whole year through to work efficiently [15].
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Figure 15: The Vitruvian or Undershot Wheel. The wheel is turned by the pressure of moving water on the paddles of the lower parts of the wheel. |
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Figure 16: The Overshot Wheel is turned by the pressure of water pouring from above into the bucket-like compartments onto its rim. |
1.5. John Smeaton Experiment
John Smeaton of England did an experiment (made public in 1759) on the efficiency of actual water wheels; namely the Undershot and Overshot Wheels. The first important result was that Overshot Wheels were about twice as efficient as Undershot Wheels; in modern terms the ratio was 66% efficient against 30%.
The second was that Overshot Wheels were driven by weight of water alone and perhaps a little more efficiency was gained by allowing the applied stream of water to strike hard against the buckets.
Lastly, it was noticed that the impact between a stream of water and a flat plate resulted in a marked loss of energy in the form of spray and turbulence. As Smeaton observed, "non elastic bodies, when acting by their impulse or collision, communicate only a part of their original power; whereas the other part being spent in changing their figure in consequence of the stroke" [16].
2. Cogwheel and Lantern Pinion Gears
The second set of mechanisms to moving would be the Cogwheel and Lantern Pinion gears (see Fig. 17). This mechanism consists of toothed wheels meshing at right angles; whereby the Cogwheel is the vertical gear and the Lantern Pinion is the horizontal gear. For this section, I will first describe the background of general Gearing, followed by a step-by-step analytical interpretation of the gears found on al-Jazari's illustration of the Third Water-Raising Device (see Fig. 1 and 8).
The first description of the Gearing was first mentioned in the ‘Mechanics' (the oldest-known engineering textbook) written by either Aristotle [Aristoteles of Stagyra (384 to 322 BCE)] or Straton [Straton of Lampsakos (pupil of Aristotle)], or both which dates to the Hellenistic era [17].
The evolution of gearing comes about from roughening the rims to reduce slippage and from this roughening, gears teeth evolved. This step may have taken some time, for cutting and filing a pair of toothed gear wheels, having the right number of teeth and transmitting rotation without jamming, is not an easy task [18].
That is to say, Gearing had been long known but rarely used because of the difficulty of making well-fitting gears [19]. However Gearing became common in the Golden Age, due to the developing technology, contributed by both Muslim scholars and craftsmen.
3. Analytical Interpretation of the Gears Found on al-Jazari's Illustration
In his illustrations, al-Jazari draws his gears (see Fig. 17) as elliptical in shape and has sharp pointed teeth as gear teeth. This might have looked crude to modern viewers but al-Jazari wanted to show his devices through perspective and colourful illustrations. It is also important to consider that modern Engineering Drawing was not known then. We will now consider a step-by-step analytical interpretation of the gears.
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Figure 17: A blown-up diagram of the gears as shown in al-Jazari's illustration. |
3.1. Why is it Elliptical in Shape?
The elliptical-shaped gear is actually a cylindrical shape tilted at an angle. For example, if you were to take a round shaped cup with its top facing you (see Fig. 18) and tilted it at an angle towards the sky, you will notice that the shape has changed to an elliptical shape (see Fig. 17).
The reason why al-Jazari wanted to draw the gears in such a way is that he might have wanted to show his drawings in an isometric view or 3D view/aspect.
3.2. Why do the Gears have Sharpened Teeth?
Consider the gears to be sharpened toothed, in mechanical terms there will be difficulties in getting them to work properly. Furthermore, it is difficult to transmit power efficiently in this manner. Thence it is concluded that at this point, when al-Jazari draw the gears (see Fig. 17), he did not want them to be constructed as shown but rather to portrait them as a drawing symbol of gears only.
3.3. Possible Relationship to the Saqiya Gears
At this point of research, it was found that the invention was a modification of the Saqiya whereby the main difference is that waterpower is used instead of animal power. There is a high possibility that the gears of the Saqiya (Cogwheel and Lantern Pinion gear) are incorporated into al-Jazari's invention since other identical mechanisms of the Saqiya could be found in the invention, such as the Sindi Wheel.
To support this statement, we may compare the Saqiya and al-Jazari's illustration of the Third Water-Raising Device (see Fig. 19-20).
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Figure 19-20: Notice the similarity of the positioning of the gears inside the red marked box. |
3.4. What did the Actual Gears Look Like?
By studying the colour illustration (see Fig. 1 and 8), it is observed that the gears might have been the Cogwheel and Lantern Pinion gear (see Fig. 21) the red-coloured gear might have most probably indicated the Lantern Pinion gear while the blue ones indicate the Cogwheel gear.
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Figure 21: The cogwheel of a Pakistani Saqiya meshing with the Lantern Pinion. |
3.5. Will the selected Gears be able to Transmit High Torque?
The design of the cogwheel is that it will be able to mesh probably into one another without slippage and furthermore gears as a pair of right angle meshing wheels did transmit high torque, as in the case of the Saqiya [20].
3.5. What are the Methods Used to Enhance its Efficiency?
The Andalusi agronomical writers Abu ‘l-Khayr and Ibn al-‘Awwam suggested practical means to enhance the efficiency and longevity of the Saqiya. They suggested that the teeth of the potgarland wheel (or the cogwheel) be made of hardwood (such as olive) whereas softwoods are employed for the Lantern Pinion [21].
4. Sindi Wheel
Last but not least, the set of mechanism used to raise water to a higher head is the Sindi Wheel, as al-Jazari prefers to call it (see Fig. 22). This name may have most probably been derived from the word ‘Sind', from the River Sind in India [22]. However, it is very similar to the chains-of-pots or potgarland, which is found in Saqiya (see Fig. 23). Thus for this section, the Sindi Wheel is described with reference to the potgarland.
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Figure 23: Note that the potgarland is inside the marked red box [23]. |
The potgarland consists of a number of earthenware pots secured between two ropes, each spliced to form a single long loop. Subsequently, the potgarland is slung over the pegs on the vertical drum [24]. As the vertical drum rotates, the rope, with the secured earthenware pots, rotates along with it. The process is such that the pots are filled with water at the bottom of their travel and discharge at the top into a head tank and subsequently to the designated areas through the aqueducts.
The first description of the potgarland was first mentioned in Roman times, from about the start of the common era [25]. It may have been most probably invented during the Roman times, incorporating the use of Noria. By studying both potgarland and Noria, it is observed that both wheels incorporated the use of earthenware pots to raise water to the aqueducts or head tank through rotation of the wheel. The main difference being that the power driven method and height of lift; for the Noria is water driven and its lift is dependent on its wheel diameter [26], whereas the potgarland is animal driven and its lift is dependent on the length of the rope.
4.1. Possible Problems Encountered?
There is a question raised by Landels with reference to the possibility of the potgarland slipping due to the out-of-balance load between the full and empty pots.
Schioler states, correctly, that the possibility of slip depends upon three factors; namely the pulls exerted by the full and empty pots, the coefficient of friction between the ropes and the pegs of the potgarland wheel.
Schioler found that there was no tendency to slip with rope and earthenware pots, but that there was such a tendency when buckets replace the pots [27].
4.2. What are the Methods Used to Enhance its Efficiency?
The Andalusi agronomical writer, Abu ‘l-Khayr and ibn al-‘Awwam suggested practical means to enhance the efficiency and longevity of the potgarland. They suggested that there would be an arrangement of five pots to every cubit (20 inches) of rope [28].
5. Where Does Water from the Lower Chamber Flow?
A common and often neglected question posed is that after water has flowed down into the lower chamber to drive the Scoop Wheel, does flooding in the lower chamber occur?
By studying al-Jazari's illustration, it is observed that there is an escapement at the bottom right end of the invention. Therefore, al-Jazari may have had thought of this point and designed an escapement.
Thence posing the next question, where does it flow to and how would the Third Water-Raising Device be employed?
We have discussed earlier [29] that the Third Water-Raising Device might have most probably been erected near an ornamental lake. Therefore the water from the lower chamber, of the device, might have flowed into the lake.
We would now consider the possible utility of the invention in other scenario, irrigating agricultural areas or supplying domestic water. It is however important to note that the expensive materials, such as copper jars and marble pillar, must be replaced by more economical materials, such as earthenware pots and wooden pillars.
5.1. Possibility 1
Agriculture was very important in that period, therefore irrigation plays an important role. The Third Water-Raising Device might have a primary role in raising water to a higher level. At the same time, it could also employ a secondary role in providing irrigation in lower land through drainage from its lower chamber. Water flows out from the lower chamber into a drainage system for irrigation in lower lands.
The Third Water-Raising Device would be located along a steep slope incline whereby river water is rushed into the pool of the device through pipe 1 and later flows out from the lower chamber back into the river through pipe 2 (see Fig. 24).
This could result in the machine working at a very fast rate in order to accommodate the speed of the river water rushing in.
5.2. Possibility 2
The argument is the same as Possibility 1, except that the device is now located near a dam whereby the flow of water into the device, through pipe 1, could be controlled and later flows out, through pipe 2, from the lower chamber into the lower stream (see Fig. 25).
5.3. Possibility 3
The machine is located beside the riverside where water is fed into the device, through pipe 1, at a controlled rate and later flows out, through pipe 2, from the lower chamber into qanat (man-made underground canals). The qanat has been known and was in use by the 8th century BC, therefore, the time scale for this statement is relevant (see Fig. 26).
6. Rudimentary Components and Materials Used by Al-Jazari
Having a clear understanding of the main mechanism as discussed earlier leads us to find out more about the rudimentary components and materials used by al-Jazari in the construction of the Third Water-Raising Device. Components ranging from bearings to the materials used will be discussed as follows.
6.1. Bearings
Bearings have been used for wheels as early as the fourth millennium BCE in lower Mesopotamia. In addition, metal-to-metal bearings were already in use by the Romans and Greeks, in which Hero of Alexandria mention, in his Mechanics, an axle whose ends were sheathed in copper and ran in copper-covered bearings.
It is difficult to assess the standard of craftsmanship attained by al-Jazari in the manufacture and fitting of his axles and bearings, since he tells us so little about them. The bearings are usually shown as rudimentary components on some of the drawings, but then, so are many other parts that we know from the text, to have been made with great care and skill. It is quite likely that they were drawn conventionally, much as a modern designer will show pitch circles for the teeth of a cogwheel.
It is justifiable to say that al-Jazari was serious towards his works, therefore he must have took great care to ensure that his wheels were running true. In static balance, this care would have been wasted if there was too much play or friction in the bearings. Thence he categorised different kinds of bearings for different uses as follow:
- bearings for small axles are called kharaza,
- bearings which were inserted into the lower ends of vertical axles are called sukurruja,
- wooden axles had iron 'acorns' (balluta) nailed to their ends, and these rotated in bearings called mukhula.
- bearings for heavy-duty are called rukn, which simply means ‘support'.
Plain wooden bearings were said to be in use in the West up to the 14th century. If this is the case, then al-Jazari was considerably in advance of European technology in this respect, since all his bearings are metal-to-metal type. He used different types of bearings for different duties and had a special term for each one. Because of the great care he took in constructing and tuning his machines it seems probable that his bearings were at least adequate, particularly when it is remembered that in most cases, the loads for the devices were light and running speeds were slow [30].
6.2. Axle
Al-Jazari made his axles of wood, copper or iron depending on the duty, and the usual word for them is mihwar, although he occasionally uses non-technical words such as qadib (stick) or saffud (rod). The Banu Musa, Archimedes and al-Khuwarizmi also use the term mihwar [31].
6.3. Lubrication
Lubrication is equally ancient, dating back to Egypt in 1800 BC. An Egyptian wall painting shows 172 men transporting a colossus from a quarry on sledges, while one man pour oil or grease ahead of the base of the statue on which he rides. In addition, Egyptian chariots had plain grease-packed bearings, which were protected from sand by leather covers.
The curious point however is that none, not one, of the classical writers, including al-Jazari, makes any mention of lubrication. It could be that they found the process of lubrication to be too common and trivial to be included in their work [32].
6.4. Pipes
The closed pipe system is of interest because al-Jazari incorporates this system to bring in water from rivers to the pool of the invention. Thence it is important to know the characteristics of the closed pipe system. Firstly, the closed pipe system is less expensive as compared to open-channel aqueduct. However, it is much more difficult to construct and requires specialised skills. Moreover, it is subjected to frequent leaks and burst, and if blockage occurs, it may have to be completely dismantled and rebuilt [33].
However, al-Jazari and Ridwan used the expression barbakh, which means a short pipe of relatively large diameter. Ridwan tells us that pipes were made by bending sheet copper to a circular cross-section and soldering the edges together. Pipes were joined together by making the end of one wider than the end of the other, and pushing the two together. The wide end was called 'female', the narrow 'male', exactly as in modern technical parlance. When pipes were to be bent, they were first filled with lead, followed by bending and allowing the lead to melt out [34].
Vitruvius suggested a method to seal the joints, crude but practical. That is when the pipeline is complete, and the water is first let into it, some wood ash should be thrown into the tank at the supply end. This will find its way into any cracks or leaks in the system, and help clogs them up. ‘Grouting' is the technical term [35].
6.5. Fittings
All the Islamic writers used similar methods of connections and fixings. The most common method is soldering, a very ancient technique, probably known 5000 years ago in Ur. Whereby nails, cotters, lugs, male-female joints and push-fit connections were also used extensively, including al-Jazari and Ridwan.
While other components such as wire (sharit) was usually made of copper, and chain (silsila) of copper or iron. Rope (habl) was made of hemp or stranded silk. The material used for making string (khayt) is seldom specified, except when it was made of silk. Hinges (namadhaj) were mentioned by al-Khuwarizmi, and were used by all the Islamic writers.
An interesting word, used frequently by al-Jazari, is shaziya, translated as 'activator', since it seems to be used for any small component, which activates another part of the mechanism. Cams, trip-lugs, push rods, etc. could all be described by this word [36].
6.6. Materials
Most of the materials used by al-Jazari are common to the other Islamic writers, with the some exceptions. The materials are categorised into two groups, namely Metals and Other Materials.
a. Metals
The common metals used are iron, lead, tin, gold, silver, copper, brass and bronze. Furthermore the mountains around Diyar Bakr have always been rich in metals. In 516/1122 a copper mine was discovered near Dhu al-Qarnayn. Iron was also plentiful [37]. Therefore these metals are available to al-Jazari, who employed them in the structure of his invention.
b. Other Materials
Al-Jazari had little interest in the use of non-metallic materials, most of which were common substances in everyday use. Wood occurs frequently, in wheels, axles and structural work. The use of lamination to produce a wheel that would not warp is of interest. Other materials used were cloth, leather, linseed oil, paints, paper, and papier mache. Papier mache was used for making Jack Figures when lightness was important, in this case, it would most probably be used for making the cow model.
6.7. Jackwork or Jack Figures
Jackwork refers to human and animal figures, and are found in the works of several Muslim craftsmen and engineers, including al-Jazari. It was thought that Muslims were generally particularly fond of these types of work, as it was some kind of toy.
Al-Jazari usually made them from beaten copper, beaten brass, wood, or papier mache. However, the detailed instructions for the manufacture of these figures are often omitted, apart from al-Jazari description of the manufacture of a copper ‘man' (shakhs), found in Category II Chapter 7.2 of his work, Kitab fi ma‘rifat al-hiyal al-handasiya [38].
7. Weights and Measurements
There was a large number of weights and measures whose values fluctuated widely, depending upon the region, and even upon the choice of the individual craftsman. Ridwan, for instance, used the span of his own hand and the thickness of his own finger for taking measurements. There is little point, therefore, in making a detailed survey of these expressions and their values. Thence only indicative values can be given and these are derived directly from Wiedemann and Hauser.
a. Weights
1 Dirham = 3 gr
1 Mithqāl = 4.5 gr
1 'Uqiya (Syrian) = 150 gr
1 Ratl (Damascus) = 1850 gr
1 Mann ≈ 1 kg
b. Measures
1 Dhirā‘ (cubit) = ½ metre
1 Shibr (span) = ½ Dhira = 25 cm.
The span is the distance between the tip of the thumb and the tip of the forefinger, when the hand is outspread. The abbreviation is sp.
The span consisted of 12 fingers, placed side by side (asba ‘ madmum). Each finger width was thus equivalent to 2 cm. The abbreviation is F. Sometimes the length of a finger (asba‘ maftūh) was used and this was equal to about 4 cm.
Small dimensions are given by the width of a barleycorn (sha‘īra). Laid 'belly to back' there were six barleycorns to 1 F. The sha‘īra was therefore equal to about 1/3 cm.
The small span (fitr) was the distance between the tips of the thumb and index finger, when outspread. This is taken to be about 16 cm.
AI-Jazari also uses the breadth of a fingernail (zufr) say about 1 cm. To indicate very small distances he uses the width of a nail-pairing (qulama) [39].
End Notes
[1] D. R. Hill, A History of Engineering in Classical and Medieval Times, op. cit., p. 128.
[2] See Appendix 11.
[3] D. R. Hill, A History of Engineering in Classical and Medieval Times, op. cit., pp. 144-145.
[4] D. R. Hill, Studies In Medieval Islamic Technology, op. cit., Category VIII, p. 4.
[5] L. Sprague De Camp, The Ancient Engineers, op. cit., pp. 146-147.
[6] See I. 3: Teaching of Islamic Engineering.
[7] Abbott Payson Usher, A History of Mechanical Inventions. Cambridge, Mass.: Harvard University Press, 1954, p. 163.
[8] L. Sprague De Camp, The Ancient Engineers, op. cit., p. 282.
[9] Al-Jazari, The Book of Knowledge of Ingenious Mechanical Devices, op. cit., Part III, p. 275.
[10] A. Y. al-Hassan & D. R. Hill, Islamic Technology, op. cit., p. 70.
[11] See section V.1.5: "John Smeaton Experiment".
[12] A. Y. al-Hassan & D. R. Hill, Islamic Technology, op. cit., p. 6.
[13] A. P. Usher, A History of Mechanical Inventions, op. cit., pp. 163-164.
[14] See section V.1.5: "John Smeaton Experiment".
[15] R. J. Forbes, Studies in Ancient Technology. Leiden: E. J. Brill, 1965, vol. 2, p. 42.
[16] Norman Smith, Man And Water: A. History of Hydro-Technology, op. cit., pp. 155-156.
[17] L. Sprague De Camp, The Ancient Engineers, op. cit., pp. 119-120.
[18] Ibid, p. 120.
[19] Ibid, p. 282.
[20] D. A. Agius & R. Hitchcock (editors), The Arab Influence in Medieval Europe, op. cit., p. 38.
[21] Th. F. Glick, Islamic And Christian Spain in The Early Middle Ages, op. cit., p. 237.
[22] See Appendix 8.
[23] Note on fig. 22 and 23 the similarity between these two devices as marked in red.
[24] A. Y. al-Hassan & D. R. Hill, Islamic Technology, op. cit., p. 39.
[25] Ibid, pp. 40-41.
[26] See Chapter III, section 2: The Noria.
[27] D. R. Hill, A History of Engineering in Classical and Medieval Times, op. cit., p. 138.
[28] Th. F. Glick, Islamic And Christian Spain in The Early Middle Ages, op. cit., p. 237. One cubit = 20 inches as stated in L. Sprague De Camp, The Ancient Engineers, op. cit., p. 68.
[29] See IV.2: Description of the Device.
[30] Al-Jazari, The Book of Knowledge of Ingenious Mechanical Devices, op. cit., Part III, pp. 275-276.
[31] Ibidem.
[32] Ibidem.
[33] J. G. Landels, Engineering in the Ancient World, op. cit., p. 42.
[34] Al-Jazari, The Book of Knowledge of Ingenious Mechanical Devices, op. cit., Part III, p. 276.
[35] J. G. Landels, Engineering in the Ancient World, op. cit., p. 44.
[36] Al-Jazari, The Book of Knowledge of Ingenious Mechanical Devices, op. cit., Part III, p. 277.
[37] Ibidem.
[38] Ibidem.
[39] Ibid, p. 278.
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by: Salim T. S. Al-Hassani and Colin Ong Pang Kiat, Thu 24 April, 2008
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