As a result of the great conquests of the first century of Islam, the Arabs became the heirs of the ancient civilizations of western Asia and north Africa. They also inherited the links that those civilizations had maintained over the centuries with their neighbours, and thereby came into possession of a considerable corpus of written material covering a wide field of knowledge, including scientific subjects. Many Greek manuscripts were preserved in Byzantium, but the Byzantines did little more than preserve, and made few significant contributions to the progress of science. Of greater significance were the Greek schools set up in Asia Minor soon after the council of Nicaea in AD 325. The Nestorian church made one of these schools, that of Edessa, their scientific centre. In AD 489 this school was transferred to Nisibin, then under Persian rule, with its secular faculties at Jundishāpūr in Khūzistān. Here, the Nestorian scholars, together with pagan philosophers banished by Justinian from Athens, carried out important research in medicine, astronomy and mathematics. To assist in instruction a number of Greek works were translated into Syriac. At about the same time the sect of the Monophysites, who like the Nestorians were subject to persecution by the Orthodox church, were working on similar lines in Syria. They also made translations of philosophical and scientific works into Syriac. A group who were to provide some of the greatest translators and scientists of Islam were the Ṣabians of Ḥarrān in Mesopotamia.

THE NATURE AND AIMS OF ALCHEMY

Many thousands of pages have been written by modern scholars on the subject of alchemy, but it cannot be said that all the obscurities that render the subject so difficult have yet been satisfactorily elucidated. These obscurities include the actual definition of the term “alchemy”, its origins in East and West, the authorship of many of the extant texts, the motives and beliefs of the alchemists, the methods they used and the identification of many of their materials. Only in the case of laboratory equipment and processes do we have any firm data, largely because most types of equipment used by the alchemists have survived into the present or recent past. Moreover, in several alchemical works, notably those of Abū Bakr Muḥammad b. Zakariyyaʾ al-Rāzī, many pieces of equipment are clearly described and illustrated and can be understood by comparing them with their modern counterparts. Even so, although the basic purposes of the equipment can usually be determined, uncertainty as to the course of a given process may remain if we do not know the precise composition of the materials being processed.

Much of the obscurity of the subject is due to its esoteric nature and the consequent use made by its practitioners of analogy, allusion and cryptic utterances. A second difficulty lies in the tendency of many writers to attribute their own work to earlier, sometimes mythological, personages.

BRIDGES

Five types of bridge are illustrated in diagrammatic form in Figure 8.1. In 'a' a simple beam bridge is shown. Almost certainly this was the earliest type of bridge: in its most primitive form it was simply a log or a stone slab laid across a ditch or a small stream. From these beginnings came the first real bridges, with prepared abutments and spans consisting of several beams on top of which timber planking was laid. Handrails would often be provided. The problem with beam bridges, at a time when the only available materials were stone or timber, was that span lengths were limited to about 15 metres for timber, including abutments, and usually about 5 metres for stone. There were, however, some remarkable multi-span stone bridges built in China from the eleventh to the thirteenth century. These had spans up to 70 feet (21.3 metres) involving the handling of stones weighing up to 200 tonnes. This type of construction was, however, extremely wasteful in materials and labour. Also, a heavy load was placed upon the foundations, which often failed. Such structures were unknown in the Islamic world where multi-span beam bridges were generally built of timber.

The origins of the ancient cantilever bridge and its modern counterpart are quite different and demonstrate one of the dangers to which the historian of technology is exposed, namely that of assuming that because two structures look similar the older must be the ancestor of the younger. The modern cantilever bridge is a development of the continuous bridge: the introduction of hinges at certain points in a continuous bridge produces a statically determinate structure. In medieval times continuous spans were not possible, since structural steel and reinforced concrete were unknown. The ancient cantilever bridge was not based upon any analytical consideration. Rather it was a development from the beam bridge.

SCIENCE

The eleventh century witnessed in Europe a quickening of intellectual life. As trade and manufacturing grew, a 'middle class', residing in the towns, also began to appear. They expressed a rising interest in secular, materialistic matters. A growth in economic activity with the emergence of a wealthier middle class also enriched the resources of the Roman Catholic Church. Greater financial resources accrued to it under the centralisation of royal power, the construction of better transportation and communications systems and a more productive economy. These means were used, among other things, for making improvements in education.

The Church was almost the sole patron of scholarship and learning in medieval Europe. Cathedral schools had a narrow objective, the preparation of clerics and priests. The level of scientific learning in these schools was low: it consisted of basic arithmetical computations, the propositions of Euclid (without the proofs), an astronomy based mainly on the folklore of Germanic tribes, rudimentary geometry and chemistry consisting of basic metallurgy and the dyeing of cloth. Nevertheless, it was from the cathedral schools that the universities were to be established, and it was mainly from the cathedral schools and early universities that Islamic knowledge was to enter the Latin West.

The great period for the dissemination of Islamic science in the West was the twelfth and early thirteenth centuries. The translation movement of the twelfth century from Arabic into Latin, whether the translations were from Greek or Islamic works, gave the necessary impetus to the growth of European science. However, before the twelfth century, some isolated instances did occur of the diffusion into Europe of Islamic knowledge. The most notable of these are linked to the names of Gerbert of Aurillac – later Pope Sylvester II – and of Constantine Africanus. Gerbert, who died in 1003 after a short papacy, studied for several years in Christian Spain and became acquainted with Arabic literature, which he may have read through Latin translations of Arabic manuscripts.

The roots of every new civilisation must be nourished by the achievements of its precursors. In the case of Islam these precursors were to be found in the Hellenistic, Roman and Byzantine civilisations, with lesser, but still significant, influences from India and China.

When Alexander the Great died in 323 BC his conquests stretched from Greece, Asia Minor, Syria and Egypt through Persia and Afghanistan and as far as the River Indus. Although his empire did not survive his death as an entity, he had managed to impose a single political unit on a larger part of the western world than anyone before him. After he died the major part of the empire was divided among his generals: Antigonus ruled Asia Minor, Syria and Palestine; Seleucus ruled Mesopotamia, Persia and the eastern parts to the borders of India; and Ptolemy ruled Egypt and Libya. The division lasted to the battle of Ipsus in 301 BC, when Seleucus added Asia Minor and Syria to his possessions. The Seleucids only managed to hold such a vast expanse of territory for some fifty years, before the Parthians took control of eastern Mesopotamia and eventually – around the end of the third century BC – most of the eastern parts of the Seleucid kingdom.

The Greek kingdom of Bactria, however, arose in 254 BC – hence almost at the same time as Parthia. It was founded by a Greek governor, Diodatus, who made himself independent of the Seleucids. Little is known about this kingdom, which was centred on the Rivers Oxus and Sughd (on which are the cities of Bukhārā and Samarqand) and at one time extended to the north Indian plain. Eventually, after endemic warfare with the Seleucids and Parthians, the Bactrian Kingdom was incorporated into the Parthian domains about 140 BC. To us the importance of Bactria lies in its position as a commercial nexus between East Asia and India on the one hand, and the Middle East and Mediterranean on the other.

In its origins and development, Islamic astronomy closely parallels the genesis of other Islamic sciences in its assimilation of foreign material and the subsequent amalgamation of the disparate elements of that material to create a science that was essentially Islamic. Before we consider the literary and observational activities of Islamic astronomers, which lasted for over a millenium, we should glance briefly at the traditional astronomy of the Arabian peninsula.

FOLK ASTRONOMY

Traditional Arabic astronomy was closely linked to the anwā' (sing. naw'), a word that denotes in the singular the acronycal (i.e. occurring at nightfall) setting of a star or constellation and the heliacal rising of its opposite. Anwā' denotes the whole system based upon the settings and rising of stars and constellations, and it also appears in the titles of a number of works that constitute a separate class of their own.

To estimate the passage of time the early Arabs possessed a primitive system. This consisted basically of two distinct elements. First, the acronycal setting of a series of stars or constellations marked the beginning of periods called naw', but within which the duration of the naw' proper was from one to seven days; the stars themselves were responsible for rain and were invoked during rain-making ceremonies. Knowledge of these anwā' enabled Beduin trained in the science to foresee the state of the weather during a given period. Secondly, the heliacal rising of the same series of stars or constellations, at six-monthly intervals, marked out the solar year by fixing the number of periods, probably about twenty-eight. Fragments of folklore that have survived suggest that this was the basis of the calendar.

Some time before Islam the Arabs learned from the Indians to distinguish the stations or 'mansions' ( manzila, pl manāzil) of the moon, numbering twenty-eight.

The Islamic heritage in mathematics incorporated a vast body of learning from earlier civilisations, but it is almost impossible to unravel the various strands that were eventually to be woven into the complex tapestry of Islamic mathematics. Only one of these strands, that provided by the Hellenistic world, can be identified with any confidence. The Hellenistic sources, which were rendered into Arabic in the ninth and tenth centuries, either directly from the Greek or through the medium of Syriac, included most of the major works of Greek mathematics. Thus we have translations of the Elements and Data of Euclid; the Conics, The Section of a Ratio and the Determinate Solution of Apollonius of Perga; the Spherics of Theodosius of Tripoli; the Introduction to Arithmetic of Nicomachus of Gerasa; and the Spherics of Menelaus, together with the works of Hero, Theon and other important Alexandrian mathematicians and commentators. Of particular importance for Islamic mathematics (and mechanics) is Archimedes, almost all of whose writings, such as The Sphere and the Cylinder, The Measurement of the Circle, The Equilibrium of Planes and Floating Bodies were translated into Arabic. There are also a number of works in Arabic, either by Archimedes or attributed to him, for which there is no original Greek. Some of the works were translated more than once and the more influential of them, such as the Elements of Euclid and the Conics of Apollonius, had a number of commentaries written about them over the centuries. The Greek tradition, both written and oral, embodied Babylonian practices, reflecting the highly developed mathematics and astronomy of Babylon. One of the most important mathematical legacies of Babylon to the Greeks and later to the Muslims, was the sexagesimal system.