2 Mr. J. N. Lockyer. On the Classification [Apr. 12, 



Detailed discussion 31 



Notes on the maps „ 33 



On the sequence of temperature of the stars in Cygnus 47 



Part IV. Sub-Gboups and Species op Gboup II. 



I. General discussion of Duner's observations 49 



The radiation flutings 52 



Chemical substances indicated by absorption flutings 54 



Tests at our disposal , 55 



II. Discussion of Duner's individual observations 56 



Consideration of the extreme conditions of spacing 56 



Origin of the discontinuous spectrum 57 



The paling of the flutings 58 



Phenomena of condensation 58 



The bands 9 and 10 59 



III. Results of the discussion 59 



The line of evolution 59 



Stages antecedent to those recorded by Duner 60 



Classification into species 61 



The sequence of the bands 61 



The question of masking 63 



The characteristics «f the various species 65 



IV. Tables- 



A. Table of the specific differences in Group II 68 



P>. Table showing the stars in Duner's catalogue arranged in species . . 70 



Pabt V. The Cause op Vabiability in Groups I and II. 



I. G-eneral views on variability 80 



II. On the variability in Group I 81 



III. On the variability in Group II '. . 82 



The frequent occurrence of variability in Group II 84 



Table of variables 85 



How the difficulty of regular variability on Newton's view is got over in 



mine 88 



The cases of small range 89 



Study of light curves 89 



Double stars 90 



Conclusion 92 



[Received March 21, 1888.] 

 Part I. — Probable Origin of some of the Groups. 

 I. Nebulce. 



In a paper communicated to the Royal Society on November 15th, 

 1887, I showed that the nebulae are composed of sparse meteorites, 

 the collisions of which bring about a rise of temperature sufficient to 

 render luminous one of their chief constituents- — magnesium. This 

 conclusion was arrived at from the facts that the chief nebula lines 

 are coincident in position with the fluting and lines visible in the 

 bunsen burner when magnesium is introduced, and that the fluting is 



