1 94 SPECIAL RESULTS IN THE URANOLOGICAL PORTION 



system changes its situation in absolute space, there may 

 thence arise, in course of time, an apparent variation in the 

 angular distance of the fixed stars. Now, as in such case 

 the position of the stars nearest to us would be more 

 affected than that of the more distant ones, the position of 

 these two classes of stars would appear altered relatively to 

 each other, although in themselves they might all have re- 

 mained unmoved. If, on the other hand, our solar system 

 is in repose, and some stars actually move, then their appa- 

 rent positions will also be altered ; and this the more as the 

 motions are more rapid, the stars in a favourable position, 

 and the distance from the earth less. The alteration in 

 their relative positions may be dependent on so great a 

 number of causes that, perhaps, many centuries may be 

 required before the laws can be discovered/' 



After Bradley, sometimes the mere possibility, and sometimes 

 the greater or less probability of the movement in space of 

 the solar system, were discussed in the writings of Tobias 

 Mayer, Lambert, and Lalande ; but William Herschel had 

 first the merit of supporting the opinion by actual observa- 

 tion (1783, 1805, and 1806). He found, what many later 

 and more exact investigations have confirmed and deter- 

 mined within narrower limits of uncertainty, that our solar 

 system is moving towards a point near the constellation of 

 Hercules in E.A. 260 44', and North Declination 26 16' 

 (reduced to 1800). Argelander, by a comparison of 319 

 Stars, and taking into account LundahFs investigations, 

 found for the situation of this point, for 1800; E.A. 257 

 54'-l ; Decl. + 28 49''2 ; and for 1850 ; E.A. 258 

 28'-5 ; Decl. + 28 45'-6 ; and Otto Struve (from 392 

 Stars) found it for 1800, E.A. 261 26'*9, Decl. + 37 



