CHAPTER XXIV 



FIXING THE BOUNDARIES OF OUR SOLAR 

 WORLD 



BY an instinct inborn to the mind, man is for ever seeking 

 limits and confines. The progress of astronomy brought a 

 natural desire to know the shape and the dimensions of the 

 planetary system to which we belong. Is Saturn at the edge ? 

 Out beyond it, amid the seeming chaos of the stars, are there 

 other " wanderers," turning and turning, like our own, about 

 the sun, but in the distance lost to view ? For more than a 

 century and a half the telescope added no new planet. Their 

 number remained at that which had been known to the ancients. 

 The optic tube had almost infinitely broadened man's ideas of 

 the extent of the system itself, and of the stars beyond ; yet 

 Saturn remained to Newton, as it was perhaps to the Chaldeans, 

 the outer rim. 



In 1781 the news slipped across Europe that the limits of 

 the solar system had suddenly been doubled. An obscure 

 musician of Bath, in England, turned amateur astronomer, was 

 sweeping the heavens with a small telescope, and was struck 

 by a curious appearance in the constellation of the Twins. It 

 was very much larger than any of the surrounding stars ; he 

 therefore suspected it to be a comet, and the attention of astro- 

 nomers was drawn thereto. The close study of the comets was 

 in the order of the day ; many attempts were made to compute 

 its path. At last it became clear that it was no comet, but that 

 it moved in a circle, nearly. It was a new planet, revolving 

 about the sun at a distance of close to twenty times that of the 

 earth. 



The discovery made a tremendous sensation, and it made 

 fame for the man whose view had held it first. For our earthly 

 concerns the later event was undoubtedly of more importance 

 than the discovery itself. It was not a wonderful discovery, 

 either in the instruments employed or in the sense of having 



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