424 On the Spectra of some of the Fixed Stars. 



The whole spectrum of Sirius is crossed by a very large num- 

 ber of faint and fine lines. 



It is worthy of notice that in the case of Sirius, and a large 

 number of the white stars, at the same time that the hydrogen 

 lines are abnormally strong as compared with the solar spectrum, 

 all the metallic lines are remarkably faint. 



On the 27th of February, 1863, and on the 3rd of March of 

 the same year, when the spectrum of this star was caused to fall 

 upon a sensitive collodion surface, an intense spectrum of the 

 more refrangible part was obtained. From want of accurate ad- 

 justment of the focus, or from the motion of the star not being 

 exactly compensated by the clock movement, or from atmospheric 

 tremors, the spectrum, though tolerably defined at the edges, 

 presented no indications of lines. Our other investigations have 

 hitherto prevented us from continuing these experiments further ; 

 but we have not abandoned our intention of pursuing them. 



15. aLYRiE (Vega). — This is a white star having a spectrum 

 of the same class as Sirius, aud as full of fine lines as the solar 

 spectrum. Many of these we have measured, but our investiga- 

 tion of this star is incomplete. 



We have ascertained the existence, in the stellar spectrum, of 

 a double line at D corresponding to the lines of sodium, of a triple 

 line at b coinciding with the group of magnesium, and of two 

 strong lines coincident with the lines of hydrogen C and F. 



16. Capella. — This is a white star with a spectrum closely 

 resembling that of our sun. The lines are very numerous ; we 

 have measured more than twenty of them, and ascertained the 

 existence of the double sodium line at D, but we defer giving de- 

 tails until we have completed our comparison with the spectra of 

 other metals. 



From this star we obtained (on February 27, 1863) a photo- 

 graph of the more refrangible end of the spectrum ; but the ap- 

 paratus was not sufficiently perfect to exhibit any stellar lines. 



17. Arcturus (aBootis). — This is a red star the spectrum of 

 which somewhat resembles that of the sun. In this also we have 

 measured upwards of thirty lines, and have ascertained the ex- 

 istence of a double sodium line at D ; but our comparisons with 

 other metallic spectra are not yet complete. 



18. Pollux. — In the spectrum of this star, which is rich in 

 lines, we have measured twelve or fourteen, and have observed 

 coincidences with the lines of sodium, magnesium, and probably 

 of iron. At any rate there is a line which we believe occupies 

 the position of E in the solar spectrum. 



a Cygni and Procyon are both full of fine lines. In each of 

 these spectra we observed a double line coincident with the 

 sodium D. 



