PLEASURES OF THE TELESCOPE. 



509 



power of such an instrument divides the star into two twinkling 

 points. They are about two and a quarter minutes of arc apart, 

 and exceptionally sharp-sighted persons are able to see them di- 



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fit 



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vided with the naked eye. Now take the three-inch telescope 

 with a moderate power, and look at them. Each of the two stars 

 revealed by the opera glass appears double, and a fifth star of the 

 ninth magnitude is seen on one side of an imaginary line joining 



VOL. XLVII. 



-42 



