408 Mr. A. S. Davis on a Theory of Nebula and Comets. 



The following figure is intended to represent a section of the 

 nebula (Lassell, pi. 2. fig. 9, Royal Astronomical Society's 

 Memoirs, vol. xxxvi.) shown on page 403. 



The parts represented by the medium shading and the light 

 shading denote, respectively, the large mass of rarer gas and the 

 small mass of denser gas. The dark shading denotes the part 

 rendered visible by chemical action. 



Immediately below is shown the mode of formation of an 



annular nebula. The mass of gas indicated by the medium 

 shading must be smaller than that indicated by the light shading, 

 and also rarer. If it were denser, it would ultimately enter into 



