Masterpieces of Science 



the conception of Copernicus, it was dwarfed by 

 the conception of stretches from star to star so 

 vast that the whole orbit of the earth was only 

 a point in comparison. 



An indication of the extent to which the diffi- 

 culty thus arising was felt is seen in the title of 

 a book published by Horrebow, the Danish 

 astronomer, some two centuries ago. This 

 industrious observer, one of the first who used an 

 instrument resembling our meridian transit of 

 the present day, determined to see if he could 

 find the parallax of the stars by observing the 

 intervals at which a pair of stars in opposite 

 quarters of the heavens crossed his meridian at 

 opposite seasons of the year. When, as he 

 thought, he had won success he published his 

 observations and conclusions under the title of 

 "Copernicus Triumphans. " But alas ! the keen 

 criticism of his contemporaries showed that what 

 he supposed to be a swing of the stars from season 

 to season arose from a minute variation in the 

 rate of his clock, due to the different temperatures 

 to which it was exposed during the day and the 

 night. The measurement of the distance even 

 of the nearest stars evaded astronomical research, 

 until Bessel and Struve arose in the early part of 

 the present century. 



On some aspects of the problem of the extent 

 of the universe light is being thrown even now. 

 Evidence is gradually accumulating which 

 points to the probability that the successive 

 orders and smaller and smaller stars, which our 

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