THE PLANET EROS. 651 



Aside from the determination of the solar parallax, Professor Pick- 

 ering has pointed out that Eros furnishes an opportunity for the in- 

 vestigation of several interesting photometric problems. These are: 

 the determination of the planet's diameter; a test of the law that the 

 light varies inversely as the square of the distance; a test of the exist- 

 ence of an absorbing medium within the solar system, and a test of the 

 law connecting the phase angle of a planet with the variation in bright- 

 ness. 



Thus Eros, the tiny asteroid, whose total area is little larger than 

 the State of Rhode Island, is for the moment of more importance in 

 the eyes of the astronomical world than the greatest planet which 

 moves about the sun. 



