MR. W. HTJGGINS ON THE 8PECTRA OF SOIVIE OF THE NEBULA. 385 



[No. 4403. 2008 h. 17 M. R.A. 18'' 12" 33«. N.P.D. 106° 13' 36". Remarkable 

 object. Bright ; extremely large ; extremely irregular figure ; 2-hooked.] 



Sir John Herschel observes of this nebula, " A most curious object, not unlike the 

 nebula of Orion (as it used to be figured like a Greek capital omega, Q). There is in 

 it a resolvable portion * or knot distinctly separated from and insulated in the rest, as 

 if it had absorbed the nebula near it. Its form is like the Greek Q, with the left {ox 

 following) base-line turned upwards. The curved or horseshoe part is very faint, and 

 has many stars in it ', the preceding base-line hardly visible. Its light is not equable, 

 but blotty "f. 



Lord OxMANTOWN informs me that in the observations of this nebula at Birr Castle 

 there is no mention of resolvability ; and that " the central part to the right of star a 

 consists of bunches or patches of bright nebulosity, with fainter nebulosity intervening." 



The spectrum of this nebula indicates that it possesses a gaseous constitution. One 

 bright line only was seen, occupying in the spectrum apparently the same position as 

 the brightest of the lines of nitrogen. When the slit was made as narrow as the 

 intensity of the light would permit, this bright line was not so well defined as the 

 corresponding line in some of the other nebulae under similar conditions of the slit, but 

 remained nebulous at the edges. 



When the brightest portion of the nebula containing the nucleus or " bright knot " 

 was brought upon the slit, in addition to the bright line a faint narrow continuous 

 spectrum was seen. 



The bright knot appeared in my telescope smaller and more condensed than it is 

 represented in the drawings of Sir John Herschel. 



[No. 4572. 2075 h. 16 H. IV. RA. 20'' 16™ 7''-9. N.P.D. 70° 20' 19"-3. A pla- 

 netary nebula ; bright ; pretty small ; round ; four stars near.] 



" Rather hazy at the edges, but not materially brighter in the middle, but no hollow. 

 It has four stars near it like satellites. Diameter in R.A. 30"4;. Its light is a little 

 mottled, but it is well defined "$. 



Lord RosSE remarks, "This planetary nebula is a beautiful little spiral. Star or 

 bright nucleus north following the middle "§. 



" Dieser Nebel hat sich seit 30 Jahren bestimmt nicht nachweisbar bewegt. Klein 

 aber ziemlich hell, 25" diam., rund und durchaus gleichformig hell ; erscheint in der 

 That wie eine Nebelscheibe." — D' Arrest ||. 



* " Mr. Mason declares the upper and larger knot to be irresolvable by his telescope (a reflector of 12 inches 

 aperture and 14 feet focal length). In this particular my observations of 1835 and 1837 so far agree, that its 

 resolvability is not mentioned Ln words or indicated in the diagrams made on those occasions." — Sir John 

 Herschel, ' Results of Astronomical Observations at the Cape of Good Hope,' p. 7, and pi. 2, fig. 1. 



t Philosophical Transactions, 1833, p. 461, and Plate XII. fig. 35. 



t Philosophical Transactions, 1833, p. 467, and Plate XIII. fig. 47. 



§ Ibid. 1861, p. 733, and Plate XXVII. fig. 34. 



II Beobachtungen der Nebelflecken und Stemhaufen, p. 349. 



