CELESTIAL MEASURINGS AND WEIGHINGS. 209 



a star hardly of the sixth magnitude invisible, therefore, 

 or but barely discernible to the ordinary unassisted eye ; 

 and it would require four hundred such suns concentred 

 into one to send us the light which that superb star 

 actually does; supposing none lost or extinguished in 

 traversing so enormous a distance : a journey which it 

 would take more than twenty years to accomplish ! We 

 speak here only of the proportion between the lights of 

 the two bodies ; but this can give no indication of that 

 between either their magnitudes or their weights or 

 masses, since the intrinsic splendour of the surface of the 

 one may, for anything we can tell, exceed that of the 

 other in any proportion. As to the proportion between 

 the masses, however, a very unexpected prospect of be- 

 ing able to ascertain it ere many years shall have 

 elapsed ; and even of forming something like a rude 

 estimate of it already, has quite recently opened to us : 

 the history of which may serve to show what persevering 

 industry will accomplish in apparently the most hopeless 

 lines of inquiry. 



(35.) Sirius, as the most conspicuous of the stars, has 

 been watched by all astronomers with the utmost assi- 

 duity as the principal of the great landmarks of their 

 science ; the chief of their list of " fundamental stars ;" 

 those to which every observer of necessity resorts to test 

 the stability of his instruments; the rates of his clocks ; 

 and every condition which gives precision to his obser- 

 vations. It has long been known, like most and prob- 

 ably all the othei stars, not to be absolutely fixed in the 

 heavens ; but subject to what we have above described 



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