222 A CENTURY'S PROGRESS IN ASTRONOMY. 



vard. In 1893 Kapteyn announced his con- 

 clusions, derived from a novel method of 

 studying the distance of the stars from their 

 proper motions. In order to reach a definite 

 idea of the distances of the stars, he made use 

 of the component of the proper motion, meas- 

 ured at right angles to a great circle of the 

 sphere which passes- through a given star and 

 the apex of the solar motion. He found that 

 stars of the first spectral type have smaller 

 proper motions than those of the second, indi- 

 cating that stars of the second type are on the 

 average nearer to the Solar System than those 

 of the first, the near vicinity containing almost 

 exclusively second - type stars. Kapteyn con- 

 cluded that the group of second - type stars 

 formed one system, named the solar cluster, 

 which he considered to be roughly spherical in 

 shape. In 1902 he abandoned this idea, retain- 

 ing, however, his opinions as to the relative 

 distances of the different types. That the 

 second -type stars are nearer to the Sun than 

 the first is, he remarked in a letter to the 

 writer, incontrovertible. 



In the investigation of the motions in, and 

 extent of, the Universe, the name of Simon 

 Newcomb stands out pre-eminently. Born in 

 1835 at Wallace, in Nova Scotia, he went to 



