VOL. XIV.] PHILOSOPHICAL TRANSACTIONS. 77 



for the distance of the tropics was between 471 ^nd 47^. Of these he chose 

 nearly the mean 47° 42' AQl', the half of which gives 23° 5l' 20*. And the 

 same in his hypothesis of the planets. But Theo, in his shorter tables, through 

 brevity omits the seconds. 



PappuSj 390 years after Christ, by Riccioli, makes it23°30'; but by Com- 

 mandine 23° 50'. 



TheOj anno 370, after Christ, 23° 51' 20". But elsewhere in round numbers 

 23° 31'. 



Prince Almamou, anno Christi 825, and the Arabian philosophers in his time, 

 make it 23° 35'. And in this number Alfraganus, in his astronomy, acquiesces. 



Mohammed Ebn Gaber Al Bategnius, at Racca, about anno Dom. 880 or 890, 

 makes it 23° 35'. In this Al Bategnius prefers his own observations before 

 Ptolemy's; and says, that with a very long alhidade or paralactic ruler, like 

 those of Ptolemy, he carefully took at Racca the distance of the tropics 47° 10', 

 that is 59° 36' — 12° 26'; and therefore the latitude of Racca 35°, which yet 

 Ulughbeg makes 36° lO', and Riccioli 36°. 



Thabet Ebn Corra, anno Dom. 1210, according to Riccioli, but rather in 

 901 , found it 33° 30'. 



Abul Hosein Ebn Suphi makes it 23° 35'. 



Abul Wafi Albuziani, and Abn Hamed Saganiensis, a very ingenious man, 

 anno Dom. 987, at Bagdad, found the obliquity very near 23° 35'. And so a 

 Persian author in Selden's Archives gives 23° 33'. As also the Persic tables of ** 



Chryococca 23° 35'. 



Al Batrun Abul Rihan, anno Dom. 995, or according to Abulfarag 1070, by 

 using a quadrant of 15 cubits radius, makes it 23° 35'. 



But Abu Jaafer Alchazan, anno Dom. 970, with his associate Abufald, at 

 Edessa, and others of that age, found it rather less than 23° 35'. 



Almaeon, son of Almansor, anno Dom. 1140, made it 23° 33' 30" according 

 to Riccioli, or 23° 33' to Clavius and Maestlin. 



Ismael Abulfeda, prince of Hama, anno Dom. 1311, retains 23° 35'; perhaps 

 on the authority of Almaemon. 



Prophat, the Jew, anno Dom. 1300 or 1303, gives 23° 32'. 



Abu Mahmud Al Chogandi, anno Dom, 992, with a sextant of 40 cubits 

 radius, and its arc divided to seconds, made it 23° 32' 21". And hence the 

 astronomer Noddam affirms, that the sun's greatest declination was hardly ever 

 found less than 23° 33'. 



Arzachel, of Spain, between anno Dom. 1070 and IO89, takes 23° 33' 30". 



The Persian Chojah Nasiroddin, at Maraga, anno Dom. 1261 or 1269, ob- 

 served the obliquity accurately, and found it to be 23° 30'. 



