**Adelard**'s life are known with certainty. We do know that he studied in Tours in the Loire Valley in west central France and that he later taught at Laon in the Picardie region of northern France. Laon lies northwest of Reims and northeast of Paris. Adelard may have taught at the theological and exegetical school there which had been founded by Anselm of Laon in about 1100.

After leaving Laon, Adelard travelled for about seven years visiting first Salerno southeast of Naples. The medical school at Salerno, considered by many to be the first "modern" European university, was a famous institution at this time, drawing students from all over Europe. From Salerno Adelard travelled to Sicily which at that time was under Norman control but still strongly influenced by Arabic traditions. The Arabs from North Africa had conquered the island in 965 and remained in control for about 100 years but the Normans gained the island in 1060.

Adelard next visited Cilicia, an ancient district of southern Anatolia which today is in Turkey. Cilicia was on the north east coast of the Mediterranean Sea and Adelard took the natural coastal route round the east end of the Mediterranean to Syria and then later to Palestine. We know that he returned to Bath and is mentioned in the records of that city for the year 1130. There is no record of Adelard visiting Spain, but many scholars have concluded that he must have visited that country to have had access to the Spanish-Arabic texts which he translated.

Certainly Adelard became an expert in the Arabic language which he might have learnt in Spain as did Gherard of Cremona a few years later. However, there is an alternative theory that he learnt Arabic in Sicily. It is quite possible that, if this were the case, then he came in contact with Spanish-Arabic texts in Sicily for several scholars who had lived in Spain were at this time in Sicily.

Adelard wrote a number of original works on philosophy. The first work that he is known to have written is a philosophy text written before 1116 and dedicated to William, Bishop of Syracuse. Since Syracuse was one of the most important cities of ancient Sicily, this work is likely to have been written around the time of Adelard's visit to that island. However, since the work is based firmly on Plato's philosophy, without any signs of Arabic influences, it may have been mostly written before Adelard's visits brought him in contact with the learning of the Arabs.

It is not as a philosopher that Adelard merits inclusion in this archive. Rather it is because he is [1]:-

Adelard made Latin translations of Euclid's... one of the translators who made the first wholesale conversion of Arabo-Greek learning from Arabic into Latin.

*Elements*from Arabic sources which were for centuries the chief geometry textbooks in the West. In fact there seem to have been three separate versions of Euclid's

*Elements*written by Adelard. Version one is a translation of the whole fifteen books (the 13 original books written by Euclid and the two further books written by Hypsicles). Adelard seems to have taken as his source one of al-Hajjaj's Arabic translations from Greek.

The second version of Euclid's *Elements* by Adelard is quite different. It contains quite different wording of the statements of the propositions to that of version one, while the proofs are often only outlines or indications of how proofs might be constructed. The style of the translation tells experts that Adelard did not produce this from his own version one, but rather that he used some unknown Arabic source different from al-Hajjaj's translations.

There is debate as to whether the third version of Euclid's *Elements* attributed to Adelard is indeed his work. It is a commentary on Euclid's *Elements* rather than a translation of the original text. We know it was written before 1200 and became quite well known under Adelard's name. Roger Bacon gives quotes from this version in his works.

Adelard also translated al-Khwarizmi's tables, wrote on the abacus and on the astrolabe. We should make some further comments on his translation of al-Khwarizmi's tables which became the first Latin astronomical tables of the Arabic type with their Greek influences and Indian symbols. These tables contain, at the end of chapter 4, the date of 26 January 1126 (at least that is what the Arabic date of A.H. 520 Muharram 1 corresponds to). It is hard to see what this date is there for unless it is the date when the chapter was completed, and so it has been taken as the approximate date for Adelard's translation. However, there is a manuscript (written later but a copy of Adelard's translation) which mentions an eclipse of the sun which took place in 1133. It is possible that Adelard's translation took place after 1133 or, equally likely, that the scribe making the later copy added information about a recent eclipse which was not in Adelard's original text.

Adelard also wrote arithmetic books, the earliest one of which was written before he studied Arabic arithmetic. It is based on the work of Boethius. A mathematics treatise which is strongly influenced by Arabic ideas has been attributed to Adelard although the attribution is not certain. The work consists of five books, the first three of which are on arithmetic and based on the Indian methods as presented in Arab writings. It has been conjectured that these books are based on an arithmetic book by al-Khwarizmi which is now lost. The remaining two books of the five which compose the treatise cover geometry, which is completely Greek in style, music, and astronomy. The astronomy, like the arithmetic, is Arabic in style.

Adelard's *Quaestiones naturales* Ⓣ consists of 76 scientific discussions based on Arabic science. In this work he promoted the use of experimental data and writes that he [1]:-

... prefers reason to authority.

**Article by:** *J J O'Connor* and *E F Robertson*