Next in importance to John of Spain as a translator of Arabic astrology in the first half of the twelfth century should probably be ranked Plato of Tivoli. They seem to have worked independently and sometimes to have made distinct translations of the same work, as in the case of the _Nativities_ of Albohali and the _Epistle_ of Messahala. On the whole, Plato’s translations[218] would appear slightly to antedate John’s. Haskins has shown, however, that the date 1116, hitherto assigned for Plato’s translation of the _Liber embadorum_ of Savasorda, should be 1145.[219] But Plato’s translation of Albohali is dated 1136, while John’s was not made until 1153.[220] In 1136 is also dated Plato’s translation of the astrological work of Almansor in the form of one hundred and fifty or so brief aphorisms, judgments, propositions, or _capitula_, which later appeared repeatedly in print. Two years later he turned the famous _Quadripartitum_ of Ptolemy into Latin. His other translations include Albucasis (Abû’l-Qâsim Chalaf b. ʿAbbâs el-Zahrâwî) on the astrolabe, Haly (ʿAlî b. Ridwân b. ʿAlî b. Ğaʿfar, Abû’l-Hasan) on nativities, and a geomancy. Most of Plato’s translations were produced at Barcelona. [Sidenote: Robert of Chester.] In a manuscript at the British Museum[221] one of Plato of Tivoli’s translations is immediately preceded in the same large clear hand, different from the smaller and later writing employed in the remainder of the manuscript, by a translation of the _Judgments_ of the astrologer Alkindi by Robert of Chester,[222] with an introduction to “my Hermann,” whom Robert commends highly as an astronomer. A letter written in 1143 by Peter the Venerable to St. Bernard tells how in 1141 he had induced two “acute and well trained scholars,” who were then residing in Spain near the river Ebro, to turn for a time from the arts of astrology which they had been studying there, and to translate the Koran. These two translators were the friends whom we have just mentioned, Hermann of Dalmatia and Robert of Chester. Robert, too, tells us in the prefatory letter to the translation of the Koran, completed in 1143, that this piece of work was “a digression from his principal studies of astronomy and geometry.” Besides such mathematical treatises as his translations of the _Judicia_ of Alkindi, the Algebra of Al-Khowarizmi, a treatise on the astrolabe ascribed to Ptolemy, and several sets of astronomical tables, including a revision or rearrangement of Adelard of Bath’s translation of the Tables of Al-Khowarizmi, Robert on February 11, 1144, translated a treatise on alchemy which Morienus Romanus, a monk of Jerusalem, was supposed to have written for “Calid, king of Egypt,” or Prince Khalid ibn Jazid, a Mohammedan pretender and patron of learning at Alexandria. Of it we shall treat more fully in another chapter. About 1150 we seem to find Robert returned to his native England and writing at London.[223] [Sidenote: Hermann the Dalmatian.]