184 HISTOEY OF ASTRONOMY. 



2. It is contradicted by the parallax of the stars so far as 

 the same has been determined. The parallax of several 

 stars of the fifth and sixth .magnitudes is greater than 

 that of most stars of the first magnitude.' The star 61 

 Cygni, of the fifth magnitude, has a parallax certainly 

 greater than what Struve has given for the average 

 parallax of stars of the first magnitude. 3. It is contra- 

 dicted by the phenomena of the binary stars. There is 

 a large number of double stars, which are proved to be 

 physically connected, and therefore both are situated at 

 nearly the same distance from the earth, while in most 

 of them there is a perceptible disparity of brightness, 

 and in some cases this disparity amounts to four mag- 

 nitudes. 



II. The distribution of the stars over the entire heavens 

 is admitted not to be uniform, nevertheless such a 

 uniform distribution is assumed for the plane of the 

 Milky Way, and the irregularities which we observe in 

 it are regarded as in part unimportant, and in part 

 ascribed to the eccentric position of the sun, and its. dis- 

 tance from the plane of the Milky Way. Hence it is in- 

 ferred that from the number of the stars of a given bright- 

 ness, we may determine the ratio of the radius of their 

 sphere to that of stars of any other brightness. 



These and several other hypotheses which are involved 

 in Struve's reasoning, Professor Encke regards as alto- 

 gether inadmissible, and he concludes that the mean 

 parallax which Struve ascribes to stars of the first mag 

 nitude (viz. 0".209) is entirely unworthy of confidence. 



