$ 66, 6 7 ] The Revival of Astronomy in the West 85 



Aristotle's writings on logic had been preserved in 

 Latin translations from classical times, and were already 

 much esteemed by the scholars of the nth and i2th 

 centuries. His other writings were first met with in Arabic 

 versions, and were translated into Latin during the end 

 of the 1 2th and during the i3th centuries; in one or two 

 cases translations were also made from the original Greek. 

 The influence of Aristotle over mediaeval thought, already 

 considerable, soon became almost supreme, and his works 

 were by many scholars regarded with a reverence equal to 

 or greater than that felt for the Christian Fathers. 



Western knowledge of Arab astronomy was very much 

 increased by the activity of Alfonso X. of Leon and Castile 

 (1223-1284), who collected at Toledo, a recent conquest 

 from the Arabs, a body of scholars, Jews and Christians, 

 who calculated under his general superintendence a set of 

 new astronomical tables to supersede the Toletan Tables. 

 These Alfonsine Tables were published in 1252, on the 

 day of Alfonso's accession, and spread rapidly through 

 Europe. They embodied no new ideas, but several 

 numerical data, notably the length of the year, were 

 given with greater accuracy than before. To Alfonso is 

 due also the publication of the Libros del Saber, a volu- 

 minous encyclopaedia of the astronomical knowledge of 

 the time, which, though compiled largely from Arab sources, 

 was not, as has sometimes been thought, a mere collection 

 of translations. One of the curiosities in this book is a 

 diagram representing Mercury's orbit as an ellipse, the 

 earth being in the centre (cf. chapter vii., 140), this 

 being probably the first trace of the idea of representing 

 the celestial motions by means of curves other than circles. 



67. To the 1 3th century belong also several of the great 

 scholars, such as Albertus Magnus, Roger Bacon, and 

 Cecco cTAscoli (from whom Dante learnt), who took all 

 knowledge for their province. Roger Bacon, who was born 

 in Somersetshire about 1214 and died about 1294, wrote 

 three principal books, called respectively the Opus Majus, 

 Opus Minus, and Opus Tertium, which contained not only 

 treatises on most existing branches of knowledge, but also 

 some extremely interesting discussions of their relative 

 importance and of the right method for the advancement 



