THE GREAT STAR MAP 551 



Provisional Results from the Examination of 1911. 



The remarkable thing here is the sudden jump from mag- 

 nitude 9-0 to 9-1, after which the further change is small. The 

 actual difference in brightness of the star is so small that it is 

 hard to believe that this discontinuity can have arisen naturally. 

 It is possible that the observer had some special rule of pro- 

 cedure when he set out to observe a star catalogued as fainter 

 than 9th magnitude — for instance, he may have arranged the 

 illumination differently. The further investigation of this matter 

 must be left until more stars have been examined ; but enough 

 has been said probably to show the value of the photographic 

 measures as a check on intricacies of personal equation. 



A new enterprise of a more important and unforeseen kind 

 arose from the discovery of the little planet Eros in 1898. Our 

 solar system, which at the time when the days of the week were 

 named contained only five planets in addition to the sun and 

 moon, is now known to consist of many hundreds, and new 

 members are being discovered almost weekly. Most of them 

 are tiny rocks, probably not more than one or two hundred 

 miles across, with no perceptible influence on the movement of 

 their more important brothers and sisters ; in fact, of no par- 

 ticular interest, as far as we can see at present. Astronomers 

 were beginning to get rather tired of the continual discoveries 

 of new small planets, which brought increased responsibility for 

 keeping watch on them and increased labour in calculating 

 their movements, without any obvious advantage from the 

 increase in our knowledge. 



It was therefore a distinctly sensational incident when one 

 of these discoveries proved to have a considerable importance, 

 owing- to the fact that the tiny object moved in an orbit which, 

 in one part, was exceedingly close to the orbit of the earth. 



