NEBULAE. 39 



Uhis first description testifies the freshness and depth of the 

 impressions produced on his mind ; but how great is the dis- 

 tance from this first sketch, made in the middle of the sev- 

 enteenth century, and the somewhat less imperfect descrip- 

 tions of Picard, Le Gentil, and Messier, to the admirable de- 

 lineations of Sir John Herschel (1837), and of William C. Bond 

 (1848), the Director of the Observatory at Cambridge, U. S. !* 

 The former of these two astronomers had the great ad- 

 vantage! of observing the nebula in Orion since 1834, 'at the 

 Cape of Good Hope, at an altitude of 60, and with a twen- 

 ty-feet reflector, by which means he was enabled to render 

 his earlier delineations of 18241826 more perfect. $ The 

 positions of 150 stars, mostly of from the fifteenth to the 

 eighteenth magnitudes, in the vicinity of 6 Orionis, were de- 

 termined. The celebrated trapezium, which is not surround- 

 ed by a nebula, is formed of four stars of the fourth, sixth, 

 seventh, and eighth magnitudes. The fourth star was dis- 

 covered (in 1666 ?) by Dominique Cassini, at Bologna ;$ the 

 fifth (Y) in 1826, by Struve ; and the sixth (a'), which is 

 of the thirteenth magnitude, in the year 1832, by Sir John 

 Herschel. De Vico, the Director of the Observatory at the 

 Collegio Romano, announced in the beginning of the year 

 1839 that he had discovered three other stars in the trapezi- 

 um with his great Cauchoix refractor. These have not been 

 observed either by Sir John Herschel or Mr. Bond. That 

 portion of the nebula nearest the almost unnebulous trapezi- 

 um, and forming, as it were, the anterior part of the head 

 above the throat, the regio Huygeniana, is speckled, and of 

 a granular texture, and has been resolved into clusters of 

 stars both by Lord Rosse's colossal telescope and by the large 



of three stars, near an indentation which one might certainly regard as 

 the Sinus Magnus. Perhaps the drawing gives only the three stars in 

 the trapezium, which range from the fourth to the seventh magnitude. 

 Dominique Qassini, moreover, boasts that he was the first who observed 

 the fourth star. 



* William C ranch Bond, in the Transactions of the American Academy 

 of Arts and Sciences, New Series, vol. Hi., p. 87-96. 



t Observations at the Cape, 54-69, pi. viii. ; Outlines, 837 and 

 885, pi. iv., fig. 1. 



t Sir John Herschel, in the Memoirs of the Astronomical Society, vol. 

 ii., 1824, p. 487-495, pi. vii., viii. The latter of these gives the nomen- 

 clature of the separate regions of the nebula in Orion, which have been 

 explored by so many astronomers. 



. $ Delambre, Hist, de V Astron. Moderne, torn, ii., p. 700. Cassini 

 reckoned the appearance of this fourth star (" aggiunta della quarta 

 Stella alle tre contigue") among the changes which had taken place in 

 the nebula of Orion in his time. 



