THE INNER PLANETS. 101 



first glance : year by year fresh discoveries are 

 announced from the Heidelberg Observatory, 

 until more than five hundred asteroids are now 

 known. 



Waning interest in the ever- increasing family 

 of asteroids was revived in 1898 by the dis- 

 covery by Karl Gustav Witt (born 1866) of a 

 small planet, to which he gave the name of Eros, 

 which comes nearer to the Earth than Mars, and 

 which is of great assistance to astronomers in the 

 determination of the solar parallax. For some 

 time prior to 1898 astronomers had considered 

 it a waste of time to search for new asteroids ; 

 but this idea is not now so popular, in view 

 of the benefit conferred on astronomy by the 

 discovery of Eros. 



Of the physical nature of the asteroids astron- 

 omers know nothing. Only the four largest 

 have been measured. For many years it was 

 supposed that Vesta, the brightest of the aster- 

 oids, was also the largest. The measures of 

 Barnard with the great Lick refractor in 1895, 

 however, showed that Ceres is the largest, with 

 a diameter of 477 miles. Pallas comes next, 

 with a diameter of 304 miles ; while the dia- 

 meters of Vesta and Juno are respectively 239 

 and 120 miles. Barnard saw no traces of atmo- 



