514 POPULAR SCIENCE MONTHLY. 



change has arisen mainly from including a larger number of stars, 

 whose motions were determined with greater accuracy. 



Former investigators based their conclusions entirely on stars having 

 considerable proper motions, these being, in general, the nearer to us. 

 The fact is, however, that it is better to include stars having a small 

 proper motion, because the advantage of their great number more than 

 counterbalances the disadvantage of their distance. 



The conclusions reached by some recent investigators of the position 

 of the solar apex will now be given. We call A the right ascension of 

 the apex; D its declination. 



Prof. Lewis Boss, from 273 stars of large proper motion found 



A = 283°.3; D = 44°.l. 



If he excluded the motions of 26 stars which exceeded 40" per century 

 the result was 



A = 288°.7;D = 51°.5. 



A comparison of these numbers shows how much the result depends on 

 the special stars selected. By leaving out 26 stars the apex is changed 

 by 5° in R. A., and 7° in declination. 



It is to be remarked that the stars used by Boss are all contained in 

 a belt four degrees wide, extending from 1° to 5° north of the equator. 



Dr. Oscar Stumpe, of Berlin, made a list of 996 stars having proper 

 motions between 16" and 128" per century. He divided them into three 

 groups, the first including those between 16" and 32"; the second be- 

 tween 32" and 64"; the third between 64" and 128". The number of 

 stars in each group and the position of the apex derived from them are 

 as follows: 



Gr. I, 551 stars; A = 287°.4; D = x45°.0 



11,339 282°.2 43°.5 



III, 106 280°.2 33°.5 



Porter, of Cincinnati, made a determination from a yet larger list 

 of stars with results of the same general character. 



These determinations have the advantage that the stars are scat- 

 tered over the entire heavens, the southern as well as the northern ones. 

 The difference of more than 10° between the position derived from stars 

 with the largest proper motions, and from the other stars, is remarkable. 



The present writer, in a determination of the precessional motion, 

 incidentally determined the solar motion from 2,527 stars contained 

 in Bradley's Catalogue which had small proper motions, and from about 

 600 more having larger proper motions. Of the latter the declinations 

 only were used. The results were: 



From small motions: A = 274°.2; D = x31°.2 

 From large motions: 276°.9 31°.4 



