18 



Mr. Huggins on the Spectra of Nehulce, ^c. [Feb. 15, 



tinuous spectrum was visible. These bodies are probably gaseous in 

 constitution. 



No. 2102 27 H.IV. 



4234 5 S. 



4403 17 M. 



4572 16 H.IV. 



No. 4499 38 H.IV. 



4827 705 H.I. 



4627 192 H.I. 



The following nebulse and clusters give a continuous spectrum : — 



No. 105 18 H.V. 



307 151 H.I. 



575 156 H.I. 



1949 81 M. 



1950 82 M. 



3572 51 M. 



2841 43 H.V. 



3474 63 M. 



3636 3 M. 



4058 215 H.I. 



4159 1945 h. 



4230 13 M. 



4238 12 M. 



4244 50 H.IV. 



4256 10 M. 



No. 



4315 

 4357 

 4437 

 4441 

 4473 

 4485 

 4586 

 4625 

 4627 

 4600 

 4760 

 4815 

 4821 

 4879 

 4883 



14 

 190 

 11 



47 

 Auw. 



56 

 2081 



51 

 192 



15 

 207 



53 

 233 

 251 

 212 



M. 



H. II. 

 M. 

 H. I. 



N.44. 

 M. 



h. 



H. I. 



H.I. 



H.V. 



H.II. 



H. I. 



H.II. 



H.II. 



H.II. 



The second part of the paper contains an account of a mode of deter- 

 mining approximatively the intrinsic brightness of some of the nebulae. 



Analysis by the prisms shows that some of the nebulse consist of lu- 

 minous gas existing in masses, which are probably continuous ; and the 

 nebulee in the telescope present not points, but surfaces, in some cases, 

 subtending a considerable angle. As long as an object remains of sensible 

 size in the telescope it retains its original brightness, except as this may 

 be diminished by a possible power of extinction belonging to celestial 

 space, and by the absorptive power of the earth's atmosphere. 



By means of a special apparatus the light of three nebulae was com- 

 pared with the light emitted by a sperm candle, burning at the rate of 

 158 grs. per hour. The results are that — 



The intensity of nebula, No. 4628 1 H. IV. =y5\5^y^th part of that of thecandle. 

 „ „ annular nebula in Lyra =^if^nd „ 

 „ „ Dumb-bell nebula =19 6-07^^ » " 



The estimation in each case refers to the brightest part of the nebula. 

 The amounts are too small by the unknown corrections for the loss which 

 the light has sustained in its passage through space and through the 

 earth's atmosphere. These values have an importance in connexion with 

 the gaseous nature of the source of the light, which the spectroscope in- 



