40 COSMOS. 



Cambridge (U. S.) refractor.=^ Man} positions of the smallei 

 stars have been determined by accurate observers of the pres- 

 ent day ; as, for instance, Lament at Munich, and Cooper and 

 Lassell in England. The first named of these employed a 

 1200-fold magnifying power. Sir William Herschel w^as of 

 opinion, from a comparison of his own observations made 

 with the same instruments, from 1783 to 1811, that altera- 

 tions had taken place in the relative brilliancy and in the 

 outlines of the great nebula of Orion. f Bouilland and Le 

 Gentil had maintained the same opinion in reference to the 

 nebula in Andromeda ; but the thorough investigations of Sir 

 tTohn Herschel have rendered the occurrence of any such cos- 

 mical changes, although formerly considered to be well estab- 

 lished, exceedingly doubtful, to say the least. 



The large nebula round i] Argus is situated in that por- 

 tion of the Milky Way which extends from the feet of the 

 Centaur, through the Southern Cross, toward the middle part 

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

 nificent elTulofence. The lijjht emanating from this region is 

 so extraordinary, that Captain Jacob, an accurate observer, 

 and a resident in the tropical parts of India, remarks, entirely 

 in harmony with my prolonged experience, " Such is the gen- 

 eral blaze from that part of the sky, that a person is imme 

 diately made aware of its having risen above the horizon, 

 though he should not be at the time looking at the heavens, 

 by the increase of general illumination of the atmosphere, re- 

 sembling the effect of the young Moon."| 



* " It is remarkable, however, that within the area of the trapezium 

 no nebula exists. The general aspect of the less kiminous and cirro;!; 

 portion is simply nebulous and irresolvable, but the brighter portion, 

 immediately adjacent to the 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 cur- 

 dling light evidently indicates, by a sort of granular texture, its consist- 

 ing 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 evidently 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 m:ide 

 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 trapszi 

 ura, but no suspicion of a star." {Memoirs of the American Academy 

 New Series, vol. iii., p. 93.) 



t Phtlos. Transact, for the year 1811, voL ci., p. 324. 



t T-ans. of the Roy. Sac. of Edinb vol. x^-., 1849, part iv., p. 4451 



