NEBULA S31 







stars have been determined by accurate observers of the 

 present day ; as, for instance, Lamont at Munich, and Cooper 

 and Lassell in England. The first named of these em- 

 ployed a 1,200-fold magnifying power. Sir William Herschel 

 was of opinion, from a comparison of his own observa- 

 tions made with the same instruments, from 1783 to 1811, 

 that alterations had taken place in the relative brilliancy and 

 in the outlines of the great nebula of Orion." Bouilland 

 and Le Gentil had maintained the same opinion in reference 

 to the nebula in Andromeda ; but the thorough investigations 

 of Sir John Herschel have rendered the occurrence of any 

 such cosmical changes, although formerly considered to be 

 well established, exceedingly doubtful, to say the least. 



The large nebula round y Argus, is situated in that portion 

 of the Milky Way, which extends from the feet of the Cen- 

 taur, through the Southern Cross, towards the middle part of 

 Argo, and is so distinguished by the intensity of its mag- 

 trapezium, forming the square front of the head, is shown 

 with the eighteen-inch reflector broken up into masses (very 

 imperfectly represented in the figure), whose mottled and 

 curdling light evidently indicates, by a sort of granular 

 texture, its consisting of stars, and when examined under the 

 great light of Lord Rosse's reflector, or the exquisite defining 

 power of the great achromatic at Cambridge, U. S., is evi- 

 dently perceived to consist of clustering stars. There can, 

 therefore, be little doubt as to the whole consisting of stars, 

 too minute to be discerned individually even with these 

 powerful aids, but which become visible as points of light 

 when closely adjacent in the more crowded parts." (Outlines, 

 p. 609.) William C. Bond, who made use of a twenty-five feet 

 refractor, having a fourteen-inch object-glass, says, " There 

 is a great diminution of light in the interior of the trapezium, 

 but no suspicion of a star." (Memoirs of the American Aca- 

 demy, new series, vol. iii. p. 93.) 



99 Philos. Transact, for the year 1811, vol. ci. p. 324. 



