ASTRONOMY 



drawn as great circles on a celestial globe, they 

 would be found to intersect in points which are 

 in the neighbourhood of 6 h of right ascension, 

 40 South, and i8\ 40 North. 



Now whatever part of the sky be examined, 

 very similar results are obtained, and so we may 

 say that the stellar system as a whole appears to 

 be moving away from a point which is not very 

 far from the bright star Vega in the constellation 

 Lyra. What is the cause of this apparent motion ? 

 The obvious answer is that it is caused by our own 

 sun with its attendant planets moving through 

 space towards the point thus indicated. This dis- 

 covery is not a recent one. As long ago as 1783 

 Sir W. Herschel arrived at a similar conclusion 

 from an examination of the motions of seven stars 

 only, and the point he indicated is not very far 

 from those found by more recent investigators. 



Though modern determinations of the position 

 of the solar apex, as this point is named, are in 

 fairly good agreement, there remain to be ex- 

 plained considerable differences between the posi- 

 tions deduced from the examination of different 

 classes of stars. The diagram (Fig. 2) shows 

 some of the stars in the constellations Lyra and 

 Hercules together with the positions of the solar 

 apex as found in different ways. 



It is not surprising that these discrepancies 

 should exist. We cannot expect the motion of the 



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