1877.] 



histor^y of Astronomy/. 



73 



sinRA 8-3956475(-) 



cot (a -&))... 11-4249751 (-) 

 tan N. Dec. 

 N. Dec... 



9-8206226 (+) 

 33° 29' 25^' 



sin E. A. . . 



cot {a — ft)) 

 tan N. Dec. 



9-2421704 (-) 

 10-5117660 (-) 



9-7539364 (+) 

 N. Dec. = 29'' 34' 24'\ 



We thus ascertain the position of the star in the time of 

 Hesiod and in that of Ovid, to have been: for that of Hesiod, 

 RA. 12 h. 5 m. 42 s.... N. Dec. 33" 29' 25"; for that of Ovid, KA. 

 12 h. 40 m. 14 s. N. Dec. 29" 34' 24". 



The next step is to compute the hour angle of the star at its 

 true rising, first for the Latitude of Boeotia, about 38 J N., secondly 

 for the Latitude of Rome, about 42"]Sr., and also the Local mean 

 time at the same moment. 



In Boeotia 



cos H A. = — tan Dec. tan lat. 



At Rome 



cos H. A. = — tan Dec. tan lat. 



tan Dec. = 

 tan lat. = 

 cos H.A. 



RA 



S.T. Feb. 19. 

 Time of Arc- 

 turus rising, 



9-8206228 

 9-9006052 



5 58 40 p.m. 



Local mean time of Sunset on 

 the same day. 5 39 p.m. 



As soon therefore as the day- 

 light had sufficiently diminished 

 for the star to be visible, it would 

 actually rise. 



tan Dec, 

 tan lat. . . 

 cos H.A. 



H.A 



S.T. May 26 

 Time of Arc 

 turns setting 

 for May 26. 

 S.T. June 6. 

 Time of Arc- 

 turus setting 

 for June 6. 



9-7539380 

 9-9544374 



16 28 



4 58 8 

 15 45 



The Sun rises at Rome on 

 May 26 about 4.35 a.m., on 

 June 6 about 4.30 a.m. Ac- 

 cording to Ovid, the star's morning setting was first visible on 

 May 26, or, as he states later on, on June 6. If we consider him 

 to have consulted two different authorities, one of which gave the 

 true, the other the visible setting of the star, no reasonable excep- 

 tion can be taken to the value of his statements. The expressions 

 the poet uses point to the time when the star's setting first occurred 

 before sunrise; this for theoretical astronomers would actually have 

 taken place about May 26, and for practical observers about June 

 6, the star setting on the first-named day at 4.28 a.m., on the 

 second at 3.45 a.m. 



Again in the Fasti of Ovid, I. 654, II. 76, we are told that 



Vol. III. Pt. hi. 6 



