Robert of Chester
Robert of Chester's activities lies in the decade from 1140 to 1150. He was an Englishman by birth and variously known as Robert of Ketton, Robertus Retinensis, and Robert of Chester. In 1141, already familiar with Arabic, he and his associate, Hermann of Carinthia, were discovered in the region of the Ebro by Peter the Venerable, abbot of Cluny, who engaged them upon a translation of the Qur'an. He has left the following further works:
- al-Kindi's ludicia (astrological judgements) at the request of Hermann of Carinthia.
- A translation of the Algebra of al-Khwarizmi, dated Segovia 1145. This was the first Latin version of the fundamental treatise, through which the name as well as the procedures of algebra penetrated Latin Europe.
- A revision for the meridian of London of Adelard's version of the tables of al-Khwarizmi preserved in manuscript Madrid, Biblioteca Nacional, 10016, fols. 8r-72v.
- A set of astronomical tables, likewise for the meridian of London in 1149-50, based upon the tables of al-Zaraqllu and al-Battani and probably adapted from a translation of the Opus astronomicum of the latter by Robert, to which Hermann of Carinthia refers in 1143 in the prefrace to his Planisphaerium. Robert's translation, however, does not survive.
- There are two astrolabe treatises transmitted under Robert's name: the one on the construction of the universal astrolabe (liber ptholomei de compositione astrolabij universalis, London 1147), and the other on the use of the normal planispheric astrolabe (Liber de officio astrolabij secundum Robertum Cestrensem). The first is not a translation from Arabic, and the second has not yet been studied.
- A translation of Morienus, De compositione alchemie, completed 11 February 1144.
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