It is almost certain that before 1143 the _Astronomy_ of Al-Battānī was again put into Latin, this time by Robert of Retines[414] (or Robert of Chester). We do not, as in the case of Plato of Tivoli’s version, possess the text of this translation, though we have what was probably Robert’s adaptation to the meridian of London of Al-Battānī’s and Az-Zarqalī’s astronomical tables. This adaptation, for 1149–1150, forms a continuation of tables for the meridian of Toledo in 1149.[415] Furthermore, Al-Battānī is cited, and some of the geographical ideas expressed in his _Astronomy_ are reflected, in the as yet unpublished _Liber de essentiis_ of Hermann the Dalmatian, who was a close associate of Robert and a student of Theodoric of Chartres. The _Liber de essentiis_ was written at Béziers in 1143.[416] Robert also adapted Adelard’s _Khorazmian Tables_ to the meridian of London.[417] Another Englishman, Roger of Hereford, was probably the maker of tables for the meridian of Toledo and certainly of a series for Hereford dating from 1178, based on tables for Toledo and Marseilles.[418] Towards the end of the century, still another Englishman, Daniel of Morley, journeyed to Spain in search of Arabic astronomical lore. Here, at Toledo, he came in contact with Gerard of Cremona. On his return to England he took with him “a precious multitude of books” and, “to explain the teaching of Toledo to Bishop John of Norwich” (1175–1200),[419] wrote a work called _De philosophia_, or _Liber de naturis inferiorum et superiorum_, the astronomy of which, as in the case of John of Holywood’s _De sphaera_, was mainly based on the writings of Al-Farghānī. GERARD OF CREMONA; JOHN OF HOLYWOOD (SACROBOSCO) At about the same time, Gerard of Cremona produced a short independent treatise, the _Theorica planetarum_,[420] which became a stock text from which later writers borrowed extensively. This is merely a summary of the _Almagest_, produced apparently before Gerard made his famous translation of that great work in 1175,[421] and is of interest to us because it contains an account of methods of transposing astronomical tables to different longitudes. It had certainly been read by the author of the London tables of 1232,[422] a set which, in addition to being of astronomical value, contains a few incidental notes of geographic importance. The _De sphaera_[423] of John of Holywood (also known as John of Halifax, or John Sacrobosco), dating from the very end of our period, includes citations from Al-Farghānī’s _Astronomy_ as well as from classical authors and was the most influential work in the field of astronomical geography of its century, though the intrinsic value of its contents was not great. ARISTOTELIANISM INTRODUCED THROUGH ARABIC WORKS