SCIENCE OF THE ROMAN PERIOD 



the sole astronomical text-book of the Middle Ages 

 both in the East and in the West, while the writings 

 of Hipparchus were allowed to perish. 



The most noted of all the writings of Ptolemy is the 

 work which became famous under the Arabic name of 

 Almagest. This word is curiously derived from the 

 Greek title 17 /-uryiW?/ crvvrafa, " the greatest construc- 

 tion," a name given the book to distinguish it from a 

 work on astrology in four books by the same author. 

 For convenience of reference it came to be spoken of 

 merely as r) /AeyiVti;, from which the Arabs form the 

 title Tabair al Magisthi, under which title the book was 

 published in the year 827. From this it derived the 

 word Almagest, by which Ptolemy's work continued 

 to be known among the Arabs, and subsequently among 

 Europeans when the book again became known in the 

 West. Ptolemy's book, as has been said, is virtually 

 an elaboration of the doctrines of Hipparchus. It as- 

 sumes that the earth is the fixed centre of the solar 

 system, and that the stars and planets revolve about 

 it in twenty-four hours, the earth being, of course, 

 spherical. It was not to be expected that Ptolemy 

 should have adopted the heliocentric idea of Aristar- 

 chus. Yet it is much to be regretted that he failed to 

 do so, since the deference which was accorded his au- 

 thority throughout the Middle Ages would doubtless 

 have been extended in some measure at least to this 

 theory as well, had he championed it. Contrariwise, 

 his unqualified acceptance of the geocentric doctrine 

 sufficed to place that doctrine beyond the range of 

 challenge. 



The Almagest treats of all manner of astronomical 

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