The Evolution of the Sciences 



its trajectory will be perturbed by their presence, 

 and the study of these irregularities may enable 

 the position and the size of these companions 

 to be determined. 



Bessel selected for his investigations two 

 of the most beautiful stars in the heavens 

 Sirius, Canis Majoris and Procyon, Canis 

 Minoris. He had determined their positions 

 relatively to neighbouring stars during a period 

 of twenty-four years, from 1820 to 1844, and 

 had acquired the conviction that certain 

 anomalies presented by the motions of these 

 stars must necessarily be due, in each case, 

 to the presence of a companion. All that 

 remained to be done was to determine the 

 position and the magnitude of these two supple- 

 mentary stars by an application of the laws of 

 universal gravitation. Now, in 1862, Clark 

 of Boston discovered, in the vicinity of Sirius, 

 a star of the tenth magnitude, occupying 

 practically the position indicated by theory. 

 The observation of this star, carried out with 

 great care and detail, furnished a brilliant 

 justification of Bessel's method. The companion 

 of Procyon was discovered in 1896 by Schoeberle 



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