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



observed in the southern hemisphere (' Observations of the Southern 

 Nebulae, made with the Great Melbourne Telescope,' Part I). It 

 is clear that in them the conditions are widely different from those 

 hitherto considered in this paper. I think that the meteor itic hypo- 

 thesis satisfactorily explains them, on the supposition that we have 

 either a very condensed swarm moving at a very high velocity 

 through a sheet of meteorites at rest, or the swarm at rest surrounded 

 by a sheet all moving in the same direction. It is a question of rela- 

 tive velocity. 



If we consider the former case, it is clear that the collision region 

 will be in the rear of the swarm, that the collisions will be due to the 

 convergence of the members of the sheet due to the gravity of the 

 swarm, and that the collision region will spread out like a fan behind 

 the swarm. 



The angle of the fan, and the distance to which the collisions are 

 valid, will depend upon the velocity of the condensed swarm. 



[Received March 26, 1888.] 

 II. Stars with Bright Lines or Flutings. 



I pointed out in my last paper that those stars in the spectra of 

 which bright lines had been observed were in all probability the first 

 result of nebulous condensation, both their continuous spectrum and 

 that of the surrounding vapour being produced by a slightly higher 

 temperature than that observed in nebulae in which similar though 

 not identical phenomena are observed. 



I have recently continued my inquiries on this point ; and I may 

 say that all I have recently learned has confirmed the conclusions I 

 drew in my last paper, while many of the difficulties have disappeared. 

 Before I refer to these inquiries, however, it is necessary to clear the 

 ground by referring to the old view regarding the origin of bright 

 lines in stellar spectra, and to the question of hydrogen. 



Reference to the Old View by which it was supposed some of the Bright- 

 line Phenomena might be accounted for. 



In the views which, some years ago, were advanced by myself and 

 others, to account for the bright lines seen in some of the " stars " to 

 which reference has been made, the analogy on which they were based 

 was founded on solar phenomena ; the " stars " in question being sup- 

 posed to be represented in structure by our central luminary. The 

 main constituent of the solar atmosphere outside the photosphere is 

 hydrogen, and it was precisely this substance which was chiefly 

 revealed by these stellar observations and in the Novas, in which 

 cases it was sometimes predominant. A tremendous development of 



