1856.] The Copemican System. 189 



The Copemican System of Astronomy among the Arabs. — By 

 A. Sprenger, M. D. 



Mons. Sedillot has, I believe, published some passages shewing that 

 the Arabs were acquainted with the Copemican system of Astro- 

 nomy, yet the following extract from the ifikmat al'ayn of Katiby, 

 (died A. D. 1272) will not be read without interest. 



" Some philosophers fancy that the earth moves towards the east 

 and that the rising of the celestial bodies in the east and their set- 

 ting in the west is owing to this motion and not to the motion of 

 the widest heavenly sphere which, they maintain to be at rest. 

 This idea is wrong. I do not however advance as an argument 

 against it that, if this was the case, a bird flying in the direction of 

 the motion of the earth would not be able to keep up with it, 

 because the motion of the earth would be much faster than that of 

 a bird, inasmuch as it returns to its place in a day and a night. Such 

 an argument is not conclusive, because it may be urged that the 

 atmosphere which is close to the earth partakes of its motion as the 

 ether partakes of the motion of the heavenly sphere. But I reject 

 this theory because all terrestrial motions take place in a straight 

 line and therefore we cannot admit that the earth should move in a 

 circle." (This is the theory of Aristotle : who says, that only the 

 heavenly bodies have the most perfect of motions, the circular). 



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