APPLIED TO THE HEAVENLY BODIES. 201 



are essentially connected with the special purpose which it suhserves, and with 

 the living beings which may inhabit the planetary worlds by which it may 

 possibly be surrounded? 



When we had obtained this new information respecting the true nature of the 

 stars, our attention was directed to the phenomena which specially distinguish 

 some of the stars. 



COLORS OF THE STARS. 



When the air is clear, especially in southern climes, the twinkling stars do 

 not all resemble diamonds ; here and there may be seen in beauteov.s contrast 

 riclilxj-colorcd gems. 



The color of the light of the stars which are bright to the naked eye is always 

 some tint of red, orange, or yelloio When, however, a telescope is employed, 

 in close companionship with many of these ruddy and orange stars, other fainter 

 stars become visible, the color of which may be blue, or green, or purple. 



Now it appeared to us to be probable that the origin of these differences of 

 color among the stars may be indicated by their spectra. 



Since we had found that the source of the light of the stars is incandescent 

 solid or liquid matter, it appeared to be very probable that at the time of its 

 omission the light of all the stars is white alike. The colors observed among 

 them must then be caused by some modification suffered by the light after its 

 emission. 



Again, it was obvious that if the dark lines of absorption were more numerous 

 or stronger in some part of the spectrum, then those colors would be subdued in 

 power, relatively to the color in which few lines only occur. These latter colors 

 remaining strong, Avould predominate, and give to the light, originally white, 

 their own tints. These suppositious have been confirmed by observations. 



Mr. Ladd will throw upon the screen the spectrum of Sirius, which may be 

 taken as an illustration of the stars the light of which is tohite. 



As might be expected, the spectra of these stars are remarkable for their 

 freedom from strong groups of absorption lines. The dark lines, though present 

 in great number, are all, with one exception, very thin and faint, and too feeble 

 to modify the original whiteness of the light. The one exception consists of 

 three very strong single lines : one line corresponding to Fraunhofer's 0, one to 

 F, and the other near G. Two of these certainly indicate the presence of 

 hydrogen. This peculiarity, which seems iuvciriably connected with colorless 

 stars, is very suggestive, and invites speculation. May it be a sign of a tempe- 

 rature of extreme fierceness ] 



Let us now examine the spectrum of an orange star. 



This diagram represents the spectrum of the brighter of the two stars which 

 form the double star a Herculis. In the sppctnmi of this star the green and 

 blue parts of the light, and also the deep red, are subdued with strong groups of 

 lines, while the orange and yellow rays preserve nearly their original intensity, 

 and therefore predominate in the star's light. 



The question yet remained to be answered, would the faint telescopic stars, 

 which are blue, green, and furple, and which are never found alone in the 

 heavens, but always under the protection of a strong ruddy or orange star, fur- 

 nish spectra in accordance with this theory ? 



With some little difiiculty, and by means of a special arrangement of the 

 spectrum apparatus, we succeeded in observing the spectra of the com])onents of 

 some double stars. There will now be thrown upon the screen the well-known 

 double star /? Cygni. In a large telescope the colors of the two stars are beau- 

 tifully contrasted, as they now appear upon the screen. The spectra of these 

 stars are now shown. The upper spectrum represents the orange star, the lower 

 one that of its beautiful blue but feeble companion. In the orange star you 

 observe that the dark lines are strongest and most closely grouped in the blue 



