388 MR. W. HUGGINS ON THE 8PECTEA OP SOME OF THE NEBULA. 



[No. 2343. 838 h. 97 M. R.A. 11" G-" 34»-8. N.P.D. 34° 13' 38"-2. Planetary; very 

 bright ; very large ; round ; very gradually, very suddenly brighter in the middle.] 



" A large uniform nebulous disk, diameter lO^-O in R.A. Quito round, very bright, not 

 sharply defined, but yet very suddenly fading away to darkness." — Sir JoHX Herschel*. 



" Two stars considerably apart in the central region, dark penumbra round each spiral 

 arrangement, with stars as apparent centres of attraction. Stars sparkling in it ; resolv- 

 able." — Lord KossEf. 



"Two stars were easily seen in this nebula formerly; since 1850 only one has been 

 seen. Not observed since April 1864." — Lord Oxmantown. 



The spectrum consists of the two brighter of the lines usually present. A continuous 

 spectrum is doubtful. Once or twice a very faint continuous spectrum was suspected. 

 —June 1866.] 



§ III. Observations of Nebuloe the spectra of which are apparently continuous. 



[No. 105. 44 h. 18 H. V. R.A. O* 32™ 45^-4. N.P.D. 49° 4' 49"-8. Very bright; 

 very gradually very much brighter in the middle.] 



" Very large, much extended. Sharp nucleus, round which for some distance the 

 nebula is bright, and then suddenly decreases ; spirality suspected." — Lord Eosse;};. 

 " Small stars seen on one occasion in the nucleus." — Lord Oxmantown. 

 Spectrum continuous. 



[No. 307. 117 h. 151 H. L R.A. l*- 17'" 26^-8. N.P.D. 81° 11' 50"-3. Very bright; 

 much brighter in the middle.] 

 Spectrum continuous. 



[No. 675. 242 h. 156 H. L R.A. 2'' 31-" 38^ N.P.D. 51° 32' 45"-9. Very bright ; 

 very large; very much extended; very much brighter in the middle §.] 



" Six stars seen in it distinctly, others suspected about centre. Nucleus suspected to 

 be composed of stars." — Lord Oxmantown. 



Centre of the nebula very bright. The spectrum of this bright central part alone was 

 satisfactorily seen. This spectrum is continuous. 



[No. 1949. 649 h. 81 M. R.A. 9^ 43'" 48^-9. N.P.D. 20° 16' 10". Extremely bright; 

 extremely large ; gradually, suddenly very much brighter in the middle.] 

 Spectrum continuous ; the red end of the spectrum wanting or very faint. 

 [No. 1950. 82 M. R.A. 9'' 43'° 52«-3. N.P.D. 19= 34' 16"-3. Very bright ; very large ; 

 very much extended, " a beautiful ray."] 



Spectrum continuous. The absence or great faintness of the red portion of the 

 spectrum more marked than in the spectrum of No. 1949. 



[No. 3572. 1622 h. 51 M. R.A. IS^ 23'" 55^-4. N.P.D. 42° 5' 4". Remarkable; 

 nucleus and ring (A) ; spiral (R).] 



* Philosophical Transactions, 1833, p. 402, also Plate X. fig. 32. 



t Ibid. 1850, p. 513, and Plate XXXVII. fig. 2. J Ibid. 1861, p. 709. 



§ See also drawing by Lord Eosse, Philosophical Transactions, 1861, Plate XXX. fig. 5. 



