AL-JAZARī, BADī‘ AL-ZAMāN ABŪ’L-‘IZZ ISMā‘īL IBN AL-RAZZāZ

(fl. Divyār Bakr, 1206)

machinery, techniques of construction.

All that we know of al-Jazarī’s life contained in the introduction to his work, Kitāb fi Ma‘rifat al-hiyal al-handasiyya (“Book of Knowledge of Mechanical Devices”). He tells us that at the time of writing his book he was in the service of Nāsir al-Dīn, the Artuqid king of Diyār Bakr, and that he had spent twenty-five years with the family, having served the father and the brother of Nasir al-Din. The Artuqids were a Turcoman dynasty who maintained a precarious autonomy during the twelfth century in Mesopotamia. By 1181, however, they had become vassals of Saladin.¹

The book, which al-Jazarī wrote at the command of Nāsir al-Dīn, is divided into fifty chapters, grouped into six categories; I, water clocks and candle clocks (ten chapters); II, vessels and figures suitable for drinking sessions (ten chapters); III, pitchers and basins for phlebotomy and ritual washing (ten chapters); IV, fountains that change their shape and machines for the perpetual flute (ten chapters); V, machines for raising water (five chapters); and VI, miscellaneous (five chapters): a large ornamental door cast in brass and copper, a protractor, combination locks, a lock with bolts, and a small water clock.

The book is clearly written in straightforward Arabic; and the text is accompanied by 173 drawings, ranging from rudimentary sketches to full page paintings. On these drawings the individual parts are in many cases marked with the letters of the Arabic alphabet, to which al-Jazarī refers in his descriptions. The drawings are usually in partial perspective; but despite considerable artistic merit, they seem rather crude to modern eyes. They are, however, effective aids to understanding the text.

It is apparent from statements made by al-Jazarī in the introduction and elsewhere, that he took pride in belonging to an international fraternity of craftsmen and in continuing the work of his predecessors. Thus he acknowledges that his monumental water clock (chapter 1 of category I) is based upon the clock of pseudo-Archimedes,² Al-Jazarī also mentions the Banū Mūsā in connection with their work on fountains and cites the treatise of Apollonius of Byzantium on an automatic musical instrument.³ Others, about whom we know little or nothing, are also named; yet elsewhere he refers to devices made by earlier workers whom he does not name. Clearly, then, many of al-Jazarā’s machines were derived from earlier models, mainly Islamic, some of which were improved versions of devices described by such classical writers as Hero of Alexandria and Philo of Byzantium. Almost certainly there was also transmission from India and the Far East.⁴ Al-Jazarī was therefore not primarily an inventor but an engineer who saw his task as the perfecting of earlier work. And, although many of his devices were designed for entertainment rather than for utility, he obviously took his work very seriously.

Of all al-Jazarī’s complete machines, perhaps only the double-cylinder slot-rod pump driven by a paddle wheel (chapter 5 of category V) is a significant contribution to the history of machines. Water clocks, candle clocks, and trick vessels, the descriptions of which occupy about three-quarters of the book, have little importance in the subsequent development of mechanical technology. It is the individual components and the constructional techniques, described by al-Jazarī in such scrupulous detail, that are of far greater importance, since centuries later many of them entered the general vocabulary of European engineering. Among the most important of these components and techniques are conical valves, casting of brass and copper in closed mold boxes with greensand, static balancing of large pulley wheels, use of wooden templates, use of a paper model in design, calibration of orifices, lamination of timber to minimize warping, use of true suction pipes rather than drowned suction (in the pump mentioned above), tipping buckets that discharge their contents auto-matically after a set time, and segmental gears.

The driving mechanism for the monumental water clock (chapter 1 of category I) provides a typical example of al-Jazarī’s methods and gives a good idea of the character of the book as a whole. The design is not original—al-Jazarī acknowledges its derivation from the water machinery in the “Ar chimedes” clock, and a similar construction was used by Muhammad al-Khurāsāni al-Sa ‘ātī for the large water clock at the Jayrūn Gate in Damascus (described by his son Ridwān).⁵ Al-Jazarī, however, undoubtedly made improvements upon the other desings. For instance, the conical valve, as described by “Archimedes,” is a rather crude device; and neither he nor al-Sa ‘ātī made an accurate flow regulator.

The water in reservoir A (see Figure 1) sank at a constant rate, and the large float B operated most of the time-recording automata by the pull of the string attached to it. The static head was kept constant in the float chamber D by means of the conical valve plug on top of float C, which entered the valve seat H at the end of tap F. When water issued from orifice G, with tap F open, it flowed momentarily from the reservoir into the float chamber, whereupon valve H closed momentarily.

Thus there was only a very slight fluctuation in the static head in the float chamber. The clock recorded the passage of solar (or temporal) hours: the hours of daylight and the hours of darkness were divided by twelve, giving “hours” of varying length throughout the year, and from daytime to nighttime. The purpose of the flow regulator was to obtain these variations by altering the static head above the orifice. The system of pipes and channels inside the regulator was constructed in such a manner that the disk E carrying the orifice could be rotated through 360 degrees.

The reservoir (about 5.5 feet high by 1.0 foot in diameter), the float chamber (about 1.25 feet high by 3.5 inches in diameter), and the two floats were all made from sheet copper, soldered along the seams. Great care was taken to ensure that the vessels were of uniform cross section. The tap, valve seat, and valve plug were made from cast bronze. Plug and seat were ground together with emery on the lathe until the valve was watertight when closed, but the plug was free to slide easily out of the seat.

For the flow regulator al-Jazarī first describes how he tested various earlier designs—for example, an equally divided semicircle and an equally divided full circle⁶—but rejected them when he found that they were inaccurate. His own solution was to calibrate the orifice, a piece of drilled onyx, in the topmost position, for the required rate of flow for the day of the summer solstice. The other positions—zodiacal “houses”, five-degree, and single-degree divisions—were determined by trial and error. These were engraved on an annulus surrounding the rotatable disk. A pointer attached to the disk (on a line passing through the orifice) extended over the annulus and was set to the appropriate degree on a given day, and to the diametrically opposed degree on that night. After manufacture, the pieces of equipment were carefully assembled on firm foundations and were brought to the vertical by using a plumb line.

The foregoing exemplifies al-Jazarī’s main virtues: careful manufacture and assembly of components, and the ability to devise real improvements on the work of his predecessors. His main faults were a tendency to be inconsistent in his dimensions and some vagueness about the positioning of equipment. Nevertheless, taking drawings and text together, it can be said that he fulfilled his declared intention of describing the devices so that they could be reconstructed by a successor. Indeed, the clock described above was reconstructed in the Science Muséum, London, for the 1976 World of Islam Festival. It works perfectly, exactly in accordance with al-Jazarī’ s intentions.

Many of the components and techniques used by al-Jazarī and his Islamic congeners reappeared in Europe, apparently as reinventions, centuries later. Casting in closed mold boxes with greensand began in Europe about 1500.⁷ The first mention of conical valves is by Leonardo da Vinci; and a float-controlled regulator for steam boilers, similar to the system described above for the water clock, was patented in England in 1784⁸ (It is important to distinguish between the use of automatically operating conical valves for feedback control and the simple lift-and-release “bath plug” type, which occurred as early as Hero of Alexandria⁹ and was also used extensively by Islamic craftsmen, including al-Jazarī.)

It is hoped that further research will tell us whether European engineers had access to Islamic ideas; and if so, how they were transmitted. A book of the Banū Mūsā (ca. 850) was translated into Latin at the end of the twelfth century by Gerard of Cremona.¹⁰ Versions of the book by al-Jazarī, and works by other Islamic engineers, may therefore also exist. It is possible, however, that by the thirteenth century, when the impetus of translation was slackening in Europe, ideas from Islam and other cultural areas were transmitted by travelers’ reports and by personal contacts among craftsmen, rather than by written descriptions.

NOTES

1. See Claude Cahen, “Le Diyār Bakr au temps des premiers Urtukides,” in Journal asiatique, 227 (1935). 219–276.

2. D. R. Hill, On the Construction of Water-Clocks (London, 1976), an annotated translation of Archimedes made from three Arabic MSS. E. Wiedemann and F. Hauser, “Uhrdcs Archimedes und zwei andere Vorrichtungen,” in Nova acta Academiae Caesarae Leopoldino-Carolinae germanieae naturae curiosoram. 103 , no. 2 (1918), 164–202. This includes a German trans. made from two of the MSS.

3. F. Hauser. “Über das Kitāb al-Hiyal,” in Abhandlungen zur Geschichte der Naturwissenschaften und der Medizin (Eriangcn, 1922), nos. 89–94; E. Wiedemann, Aufsätze zur arabtschen Wissenschaftsgeschichte, II (Hildesheim. 1970), 50–56, which includes a German trans, of the Apoilonius MS.

4. In ch. 4 of category V, al-Jazar– refers to the chain of pots as a “Sindī wheel.” Several times he mentions a metal that he calls isfadruh. According to al-Dimashq– (quoted by Wiedemann in Aufsätze II, 120) this metal originated in China. At the present state of knowledge, other cultural borrowings cannot be identified with certainty.

5. E. Wiedemann and F. Hauser, “Übcrdie Uhren in Bereieh der islamischen Kultur.” in Nova acta Academiae Caesarae Leopoldino-Carolinae….100(1915), 167–272.

6. The pseudo-Archimedes used the semicircular regulator and mentions the full circle. Al-Sa’ātī used the full circle. These designs incorporate two errors: that the variation of daylight throughout the year follows a sine curve, and that the rate of flow is proportional to the static head.

7. Cyril Stanley Smith, “The Early History of Casting, Moulds and the Science of Solidification.” in W. W. Mul-lins and M. C. Shaw. eds.. Metal Transformations (New York, 1968), 23. Al-Jazarī makes it clear that the technique was well-established in Mesopotamia during his lifetime.

8. F. M. Feldhaus, Die Technik (Wiesbaden, 1970). 499; Otto Mayr, “The Origins of Feedback Control,” in Scientific American, 223 (Oct, 1970), 113.

9.The Pneumatics of Heron of Alexandria, facs, of 1851 Woodcroft ed., with intro, by Marie Boas Hall (London, 1971), 37.

10. The MS is Madrid, Biblioteca Nacional, 10010. This is a mathematical treatise, not the machine book mentioned in Note 3. An English version of the latter is being prepared by the present author.

BIBLIOGRAPHY

Al-Jazarī’ s book has not been published in Arabic, although a number of MSS are extant. There is, however, a full English ed.: Donald R. Hill, The Book of Knowledge of Ingenious Mechanical Devices (Dordrecht, Netherlands, 1974). This is a complete trans, of al-Jazarī’ s work, made mainly from MS Graves 27 at the Bodleian Library, Oxford. All the original illustrations are included as unaltered photographs with the text, and in addition there are thirty-two plates of the miniature paintings from two Istanbul MSS. Notes are provided for each chapter, in many cases with explanatory drawings; and the “General Notes” discuss al-Jazarā’ s machines, components, and techniques in a historical context. The MSS are described, and their locations and references given, on 3–6 (to which should be added Topkapi Seray, nos. A3350 and H4I4).

The only earlier work of any significance is a series of seven articles in German periodicals, written by E. Wiedemann and F. Hauser between 1908 and 1921. Partly translations and partly paraphrases, they deal with the complete book and are listed by Hill (see above) in the bibliography and by Coomaraswamy (see below) on 20–21.

Two of the five MSS in Istanbul were dated a.d. 1315 and a.d. 1354. Miniature paintings from both of these are in public and private collections, and some articles have been written about them from an artistic viewpoint. The most important of these are A. K. Coomaraswamy, The Treatise of al-Jazarl on Automata (Boston, 1924); and Freer Gallery (Washington, D.C.), folder sheets 30.71 and 32.19.

Donald R. Hill