SECT. iv. SPECTRA OF NEBULAE. 163 



which, were not compared with these stars, but Mr. 

 Hugging concludes that many of those dark lines are 

 due to new unknown elements existing in these stars, 

 and that we cannot assume that the sixty-five simple 

 terrestrial elements constitute the entire primary ma- 

 terial of the universe. A community of matter, how- 

 ever, exists throughout the visible creation ; for the stars 

 contain many of the elements common to the sun and 

 earth. ' It is remarkable that the elements most widely 

 diffused through the host of stars are some of those 

 most closely connected with the living organism of our 

 globe, including hydrogen, sodium, magnesium and iron. 

 May it not be that, at least, the brighter stars are like 

 our sun, the upholding and energizing centres of systems 

 of worlds adapted to the abode of living beings ? ' 



With regard to the nebulae Mr. Huggins's observations \ 

 show that nine are gaseous, the spectra of six exhibiting | \^ 

 three bright lines, one shows an additional faint line J 

 also, while the spectra of the dumb-bell nebula and 

 the annular nebula in Lyra show the brightness of 

 three green lines only. The spectra of eight other 

 nebulae were continuous, showing that their light has 

 not undergone any modification on its way to us. 



Mr. Huggins has been able to discriminate between/ 

 the light of the nucleus of a comet and that of its tail.! 

 The nucleus is self-luminous, and its substance is inj 

 the form of ignited gas. The coma shines by reflected 

 light as clouds do, and observations of the spectra giveS 

 reason to believe that comets chiefly consist of nitrogen). > 

 and another elementary body different from nitrogen; 

 combined with it. 



The terrestrial elements found in the fixed stars show 

 that, like the sun, they have an intensely luminous nu- 

 cleus : but if it be taken for granted that highly heated 

 gases are non-luminous internally, the planetary nebula 

 and the great nebula in Orion itself being thus considered 



if 2 



