NEBULA. 333 



by means of the telescopic star-gauges 3,138 stars have been 

 found for every mean square degree between R. A. 9h. 50m. 

 and llh. 34m. These numbers even increase to 5,093 in the 

 sweeps for R. A. llh. 24m. that is to say, for one square 

 degree of the firmament, a number of stars greater than those 

 which are visible to the naked eye in the horizon of Paris or 

 Alexandria, from the first to the sixth magnitude. 73 



The nebula in Sagittarius, which is of considerable size, 

 appears as if composed of four separate masses (R. Asc. 

 17h. 53m.; N. P. Decl. 114 21'), one of which is again 

 three-membered. All are interrupted by spots free from 

 nebulous matter, and the whole was imperfectly observed by 

 Messier. 74 



The nebula in Ci/gnus are several irregular masses, one of 

 which forms a very narrow divided band, passing through 

 the double star ^ Cygni. Mason was the first to recognize 

 the connection of these masses, so widely different, by means 

 of a singular cellular tissue. 75 



The nebula in Vulpes was imperfectly seen by Messier (No. 

 27 of his Catalogue) when he was making an observation of 

 Bode's Comet in 1779* Sir John Herschel was the first who 

 delineated and accurately determined its position (R. Asc. 

 19 52'; N. P. Decl. 67 43'). This nebula, which is not of 

 an irregular form, first received the name of the " Dumb- 

 bell," on the application of a reflector with an eighteen-inch 

 aperture. (Philos. Transact, for 1833, No. 2060, fig. 26; 



73 Cosmos^ vol. iii. p. 142. 



74 Observ. at the Cape, 24, pi. 1. fig. 1. No. 3721 of the 

 Catalogue ; Outlines, 888. 



T8 The nebula in Cygnus, partly in R. Asc. 20h. 49m. ; 

 N. P. Decl. 58 27'. (Outlines, 891.) Compare Catalogue 

 of 1833, No. 2092, pi. xi. fig. 34. 



