LITERATURE OP THE ARABS. 105 



of moment was undertaken without previously ob- 

 taining the concurrence of the heavenly bodies. 



The most flourishing period of Arabian astronomy 

 was the reign of Almamoun, who was himself de- 

 voted to the study of this science. He caused a 

 complete digest of it to be composed by the most 

 eminent men of his court, and provided at his own 

 cost the necessary instruments of observation. The 

 land of the Chaldeans still supplied the same spa- 

 cious level, the same unclouded horizon ; and under 

 his munificent patronage the philosophers of Bag- 

 dad, first on the plains of Shinar, and a second time 

 on those of Cufa, accurately measured a degree of 

 the great circle of the earth, and determined at 

 24,000 miles the entire circumference of our globe. 

 The process by which this remarkable measurement 

 was conducted is described by Abulfeda, from the 

 relation of Ibn Khallican and the best historians. 

 The obliquity of the ecliptic was calculated at about 

 twenty- three degrees and a half; but not a single 

 step was made towards the discovery of the solar 

 system beyond the hypothesis of Ptolemy. 



Among the Arabian astronomers were several who 

 distinguished themselves both by their writings and 

 observations. Albumazar published an Introduction 

 to Astronomy ; a Treatise on the Conjunction of the 

 Planets ; and another on the Origin, Derivation, 

 and End of the World. The celebrated Alfragani 

 composed a classical work entitled Elements of As- 

 tronomy, of which a translation, with notes, has 

 been given by Professor Golius, and which presents 

 a concise exposition of Ptolemy's Almagest. This 

 author likewise produced a treatise on solar clocks, 

 and on the astrolabe. Mohammed ibn Musa, Ab 



