1^2 CLASSICS OF MODERN SCIENCE 



These are, shortly, that at first collisions produce luminosity among 

 the colliding particles of the swarm, and the permanent gases are 

 given off and fill the interspaces. As condensation goes on, the tem- 

 perature at the center of condensation always increasing, all the mete- 

 orites in time are driven into a state of gas. The meteoritic bom- 

 bardment practically now ceases for lack of material, and the future 

 history of the mass of gas is that of a cooling body, the violent mo- 

 tions in the atmosphere while condensation was going on now being 

 replaced by a relative calm. 



The absorption phenomena in stellar spectra are not identical at 

 the same mean temperature on the ascending and descending sides 

 of the curve, on account of the tremendous difference in the physical 

 conditions. 



In a condensing swarm, the center of which is undergoing mete- 

 oritic bombardment from all sides, there cannot be the equivalent of 

 the solar chromosphere; the whole mass is made up of heterogeneous 

 vapor at different temperatures and moving with different velocities 

 in different regions. 



In a condensed swarm, of which we can take the sun as a type, all 

 action produced from without has practically ceased ; we get relatively 

 a quiet atmosphere and an orderly assortment of the vapors from top 

 to bottom, disturbed only by the fall of condensed metallic vapors. 

 But still, on the view that the differences in the spectra of the heavenly 

 bodies chiefly represent differences in degree of condensation and tem- 

 perature, there can be au fond, no great chemical difference between 

 bodies of increasing and bodies of decreasing temperature. Hence we 

 find at equal mean temperatures on opposite sides of the temperature 

 curve this chemical similarity of the absorbing vapors proved by many 

 points of resemblance in the spectra, especially the identical behavior 

 of the enhanced metallic and cleveite lines. 



CELESTIAL DISSOCIATION 



The time you were good enough to put at my disposal is now 

 exhausted, but I cannot conclude without stating that I have not yet 

 exhausted all the conceptions of a high order to which Fraunhofer's 

 apparently useless observation has led us. 



The work which to my mind has demonstrated the evolution of the 



