452 Pi-oceedi)uj8 of tlie lie yal Irish Academy. 





GeOIjP B. 





Montucla.^^ 

 BaiUy." 

 Delambre.^® 

 Yince.18 



"Woodbouse^" (pre- 



stimably). 

 ^bevell?-! 



Martin. ^- 



BaU.^ 

 Newcomb.^^ 

 Young.^' 

 Beny.-^ 



21 Hist, of Induct. Sciences, vol. i., p. 144. 



22 Mems. de I'Acad. des Inscriptions, voL 



VIII., Pt. I., 1869, p. 438. 



23 Great Astronomers, p. 5. 



24 Popular Astron., p. 19. 



25 General Astron., 2nd ed., p. 132. 



26 Hist, of Astron., p. 52. 



16 Hist, des Maths., vol. i., p. 264 (1802). 



17 Astron. Modeme [stc), vol. i., pp. 109, 



no. 



18 Astron. Ancienne, vol. 11., pp. 247, 249, 



250, and Biogr. Generale, under "Hip- 



parchus," p. 399. 

 IQ Astron., vol. ii., p. 257. 

 20 Astron., p. 339, presumably. 



(1^) Montucla, in the first ed. of Ms Hist, des Matts., represented the title of 

 Hipparchus' tractate on the precession as " Concerning the Eetro gradation of the 

 equinoctial points," -which he took literally ; thus placing himself in our Group B. 

 But perceiving after\rards that Hipparchus' word /j-eTanTwcrLS means only 'shifting,' 

 he, in his last ed., transfers himself -to our Group A. In this, ho'n'ever, he makes a 

 mistake, hecause if there he any shifting of the equinoctial points, it must he a 

 retrograde one, so that he still belongs to Group B. 



(1") BaUlyjin his Astron. Modeme, vol. i., p. 109, near bottom, and p. 110, puts 

 himself into Group B ; but by a curious slip of the pen, in p. 553, he makes Hip- 

 parchus explain the precession of the equinoxes by the progression of the stars and 

 the retrogradation of the equinoctial points. 



jS'one of tbese, except Eiceioli, refer to tbe existence of any 

 difference of opinion on tbe subject. 



Some of tbose in Group B are not content witb merely asserting 

 tbe alternative tbat tbey bare cbosen for Hipparcbus ; but, for greater 

 empbasis, tbey likeTvise exclude tbe otber. See, for instance, 

 Delambre, wbo says^ : " for it was not to tbe stars tbat be [Hipparcbiis] 

 attributed tbis movement ; but to tbe equinox, from wbicb all tbe 

 longitudes are reckoned." 



Tbe above writers give no reasons for tbeir conflicting opinions ; 

 but some of tbose in Group B are plainly influenced by tbe considera- 

 tion tbat sueb a man as Hipparcbus would naturally see tbe matter 

 from wbat we know to be tbe correct point of view. 



Tbere are a few writers wbo do not let us see to wbicb Group 

 tbey belong ; as tbougb it were a matter of indifference wbetber 

 Hipparcbus believed tbe stars to move progressively, or tbe equinoctial 

 points retrogressively. 



Since our teacbers do not agi'ee togetber to answer tbis question for 



' Biogr. Generale, under " Hipparque," p. 399. 



