STELLAR ASTRONOMY 413 



This would be very serious. 



For my part, I take these data to be the most important we have, 

 an importance that will immensely increase as time advances. 

 Moreover, the problem before us is of such difficulty and our means 

 of attack so slender that it seems downright sin to neglect any data 

 at our disposal. Besides, even if we neglect the proper motions and 

 confine our attention to the magnitudes and numbers, \ve do not 

 escape the necessity of hypotheses not better founded than that of 

 the random distribution of the directions of the motions. It must 

 be owing to this scarcity of data and to the hypotheses introduced 

 that Seeliger has brought out a law of the densities 1 which astro- 

 nomers will hardly be inclined to accept without strong further con- 

 firmation, because it assigns to the sun a very exceptional place in 

 the system. 



What then? Must we be content to sit absolutely idle, saying that 

 the time has not come to make a beginning ? 



What astronomer of the present day will feel inclined to have this 

 view? 



I think that we are perfectly justified in starting from an hypo- 

 thesis which has already won its spurs, which has not been shown 

 to clash with observed facts, and to develop its consequences to the 

 utmost. 



If in doing this we continue to be able to represent all the known 

 facts, our confidence in the hypothesis will have been strengthened, 

 and we may use it with a lighter heart in further research. 



If, on the other hand, we are thus led into evident contradiction 

 with the observations, the hypothesis will still not have been unpro- 

 ductive. For it will have called our attention to anomalies, the 

 knowledge of which will be helpful in replacing our hypothesis by 

 another which will embrace them. Such anomalies have indeed 

 shown themselves earlier, and to a far greater amount, than I had 

 expected. 



In trying to derive the law of the velocities, and again in trying 

 to apply the method separately to the Milky Way and to other 

 regions, anomalies were found which in the end turned out to have 

 a very systematic character. This systematic character is so pro- 

 nounced that it is in the highest degree surprising that they have 

 escaped notice so long. 



Still, as far as I know, such is the fact, with a single exception. 

 To Kobold belongs the honor of having, as early as 1895, called 

 attention to a fact which proves that our fundamental hypothesis 

 must very sensibly deviate from the truth, and which, if he had tried 

 to separate it more effectively from the effect of the solar motion, 



1 See Betrachtungen ilb. die rauml. Vertheil. des Fixsterne. Abh. der k. bayer. 

 Abh. der Wiss. n, Cl. xix, Bd. in, Abth. page 603. 



