» CELESTIAL CHEMISTRY. 245 



defined in outline to admit of accurate measurement. By means 

 of a series of micromctric observations, it will be possible to ascer- 

 tain, whether any considerable alteration in size takes ]3lace in. 

 nebulas. 



''Meteors. — Mr. Alexander Herschel has recently succeeded in 

 subjecting another order of the heavenly bodies to prismatic anal- 

 ysis. He has obtained the spectrum of a bright meteor, and also 

 the spectra of some of the trains which meteors leave behind 

 them. A remarkable result of his observations appears to be that 

 sodium in the state of luminous vapor is present in the trains of 

 most meteors. 



" Conclusion. — In conclusion, the new knowledge, that has been 

 gained from these observations with the prism, may be summed up 

 as follows : — 



"1. All the brighter stars, at least, have a structure analogous 

 to that of the sun. 



" 2. The stars contain material elements common to the sun and 

 earth. 



"3. The colors of the stars have their origin in the chemical 

 constitution of the atmospheres which surround them. 



"4. The changes in brio:htness of some of the variable stars 

 are attended with changes in the lines of absorption of their 

 spectra. 



" 5. The phenomena of the star in Corona appear to show that, 

 in this object at least, great physical changes are in operation. 



" 6. There exist in the heavens true nebula. These objects 

 consist of luminous gas. 



" 7. The material of comets is very similar to the matter of the 

 gaseous nebulae, and may be identical with it. 



"8. The bright points of the star-clusters may not be in all 

 cases stars of the same order as the separate bright stars. 



" It may be asked. What cosmical theory of the origin and rela- 

 tions of the heavenly bodies do these new facts suggest? It 

 would be easy to speculate, but it appears to me that it would not be 

 philosophical to dogmatize, at present, on a subject of which we 

 know so very little. Our views of the universe are undergoing 

 important changes. Let us wait for more facts, with minds unfet- 

 tered by any dogmatic theory, and therefore free to receive the 

 obvious teaching, whatever it may be, of new observations." 



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