194 HISTOEY OF ASTRONOMY. 



to the sun's distance, is 117 million times the mass of the 

 sun. 



The preceding conclusions are certainly wonderful ; 

 but, unfortunately, they rest upon a very unsatisfactory 

 basis. Professor Madler has subjected the stars in the 

 neighborhood of Alcyone to a very careful examination, 

 and finds decisive indications of the sun's relative motion, 

 as it had been previously established by the labors of 

 Argelander and others. But beyond the neighborhood of 

 the Pleiades, the number of stars examined is altogether 

 too small to form the basis of so important conclusions. 

 Sir John Herschel pronounces it almost inconceivable, 

 that any general circulation of the stars can take place 

 out of the plane of the Milky Way, while the Pleiades 

 are situated 20 degrees out of this plane. It is not, how- 

 ever, presumptuous to expect that the problem which 

 Madler has propounded will one day be resolved. A 

 careful determination of the proper motion of a con- 

 siderable number of stars suitably situated in different 

 parts of the heavens, could not fail to settle the question. 



M. Struve has made a careful comparison of the places 

 of the stars observed at Dorpat, with their places as de- 

 termined by other astronomers, for the purpose of dis 

 covering their proper motion. The whole number of 

 stars which formed the subject of research amounted to 

 1662, of which there were 734 single stars and 928 double 

 stars. From these researches, M. Struve concludes that 

 the angular motions of the different classes of stars are 

 inversely proportional to their distances, from which he 



