168 HISTORY OF ASTRONOMY. 



has deduced a parallax of 0".07. Taking the mean of 

 all these determinations, M. Peters has obtained as a final 

 result the parallax of the pole-star 0".106, or about one 

 tenth of a second, a distance which light would require 

 30 years to traverse. According to this result it must 

 have been 30 years after the pole-star was placed in the 

 firmament before its light shone upon the earth ; and if it 

 were now annihilated, it would still shine for 30 years 

 longer to guide the mariner across the ocean. 



M. O. Struve has recently announced that he has found 

 the parallax of a Cassiopeae to be 0".34 with a probable 

 error of 0".05 ; and the parallax of a Aurigae to be 0".30 

 with a probable error of 0".04. 



M. Peters has also attempted to determine the average 

 value of the parallax of stars of the different magnitudes. 

 For this purpose, he availed himself of the long series of 

 observations made at Dorpat, and concludes that the 

 average parallax of stars of the second magnitude is 

 0".116. Combining this result with the relative distances 

 of stars of the different orders as determined by M. 

 Struve, we are enabled to estimate the parallaxes of the 

 stars of the various orders, and hence their absolute dis- 

 tances. The following is M. Peters' result for stars of 

 the first six magnitudes : 



App. mag- p ara n ax< Distance in radii of Time required for light to 



nitude. the earth's orbit. traverse this distance. 



1 0".209 986,000 15 years. 



2 0".116 1,778,000 28 " 



3 0".076 2,725,000 43 " 



4 0".054 3,850,000 61 " 

 6 0".037 5,378,000 85 " 

 6 0".027 7616,000 120 " 



