1872.] 



some Stars towards or from the Earth. 



391 



a Ursce majoris. — The spectrum of this star is different from the 

 spectra of the other bright stars of this constellation. The line at F is not 

 so strong, while the lines at b are more distinct, and are sufficiently strong 

 for comparison with the bright lines of magnesium. The bright lines of 

 this metal fall on the less refrangible side of the dark lines, and show a 

 motion of approach of from 35 to 50 miles per second. The earth's 

 motion of 11*8 miles from the star must be added. 



y Leonis and e Bodtis. — In both these double stars the compound 

 spectrum due to the light of both component stars was observed. Both 

 stars are most conveniently compared with magnesium. I do not consider 

 my observations of these stars as quite satisfactory, but they seem to show 

 a movement of approach ; but further observations are desirable. 



The stars y Cygni, a Peyasi, y Pegasi, and a Andromeda were com- 

 pared with hydrogen on one night only. It is probable that these stars are 

 approaching the earth, but I wish to reobserve them before any numerical 

 estimate is given of their motion. 



y Cassiopeia. — On two nights I compared the bright lines which are 

 present in its spectrum at C and F with the bright lines of terrestrial hy- 

 drogen. The coincidence appeared nearly perfect in spectroscope C with 

 eyepieces 2 and 3 ; but on the night of best definition I suspected a minute 

 displacement of the bright line towards the red when compared with H /3. 

 As the earth's orbital motion from the star at the time was very small, 

 about 3*25 miles per second, which corresponds to a shift that could not 

 be detected in the spectroscope, it seems probable that y Cassiopeia? has a 

 small motion of recession. 



In the calculation of the estimated velocities the wave-lengths employed 

 are those given by Angstrom in his * Recherches sur le spectre solaire ' 

 (Upsal, 1868). The velocity of light was taken at 185,000 miles per 

 second. 



The velocities of approach and of recession which have been assigned to 

 the stars in this paper represent the whole of the motion in the line of sight 

 which exists between them and the sun. As we know that the sun is 

 moving in space, a certain part of these observed velocities must be due to 

 the solar motion. I have not attempted to make this correction, because, 

 though the direction of the sun's motion seems to be satisfactorily ascer- 

 tained, any estimate that can be made at present of the actual velocity with 

 which he is advancing must rest upon suppositions, more or less arbi- 

 trary, of the average distance of stars of different magnitudes. It seems 

 not improbable that this part of the stars' motions may be larger than 

 would result from Otto Struve's calculations, which give, on the supposition 

 that the average parallax of a star of the first magnitude is equal to 

 0"'209, a velocity but little greater than one fourth of the earth's annual 

 motion in its orbit. 



It will be observed that, speaking generally, the stars which the spectro- 



