102 A CENTURY'S PROGRESS IN ASTRONOMY. 



sphere round any of the asteroids. It should 

 be stated that in 1872 Vogel thought he could 

 detect an " air-line " in the spectrum of Vesta : 

 he admitted that the observation required con- 

 firmation, but it has not been corroborated either 

 by himself or any other observer. 



