38 



Trans. Acad. Sci. of St. Louis. 



plained in some other way. The diffuse nebulae are cold, 

 infinitely rare, and almost free from pressure ; the Sirian stars 

 are intensely hot, relatively dense, and subject to enormous 

 gravitational pressure. 



The Astronomical Journal, No. 455. 



Law of Temperature for Gaseous Celestial Bodies 

 Condensing under the Law of Gravitation. 



T. J. J. See, May 6, 1898. 



1 i Class I 

 J Sirian Stars 



Class III 

 Orange Stars 



Planetary Nebulas Diffused HelulM*^ 



^ AXIS OP EADIUS R 



CURVE OF TEMPERATURE FOR GASEOUS STARS AND NEBULAS, A REC- 

 TANGULAR HYPERBOLA REFERRED TO ITS ASYMPTOTES. 



(c. ) /Stars of the second class have not yet reached the maxi- 

 mum temperature. Stars of the second class, of which our 

 Sun is an example, are conceded to be at lower temperatures 

 than those of the first class, and the question arises whether 

 their temperatures are rising or falling. The Sirian stars are 

 surrounded by dense hydrogen atmospheres, which produce 

 the heavy absorption observed in their spectra. As the 

 heights of atmospheres of gases of different molecular 

 weights under any given condition are known to be inversely 

 as the molecular weights, it follows that when a star is so far 



