MEDI/EVAL SCIENCE AMONG ARABIANS 



as to the accuracy of the measurement. It is in- 

 teresting to note, however, that the two degrees were 

 found of unequal lengths, suggesting that the earth is 

 not a perfect sphere a suggestion the validity of which 

 was not to be put to the test of conclusive measurements 

 until about the close of the eighteenth century. The 

 Arab measurement was made in the time of Caliph 

 Abdallah al-Mamun, the son of the famous Harun-al- 

 Rashid. Both father and son were famous for their 

 interest in science. Harun-al-Rashid was, it will be 

 recalled, the friend of Charlemagne. It is said that he 

 sent that ruler, as a token of friendship, a marvellous 

 clock which let fall a metal ball to mark the hours. 

 This mechanism, which is alleged to have excited great 

 wonder in the West, furnishes yet another instance of 

 Arabian practicality. 



Perhaps the greatest of the Arabian astronomers was 

 Mohammed ben Jabir Albategnius, or El-batani, who 

 was born at Batan, in Mesopotamia, about the year 

 850 A.D., and died in 929. Albategnius was a student 

 of the Ptolemaic astronomy, but he was also a prac- 

 tical observer. He made the important discovery of 

 the motion of the solar apogee. That is to say, he 

 found that the position of the sun among the stars, at 

 the time of its greatest distance from the earth, was 

 not what it had been in the time of Ptolemy. The 

 Greek astronomer placed the sun in longitude 65, 

 but Albategnius found it in longitude 82, a distance 

 too great to be accounted for by inaccuracy of meas- 

 urement. The modern inference from this obser- 

 vation is that the solar system is moving through 

 space; but of course this inference could not well be 



IS 



