A HISTORY OF SCIENCE 



advantages of these telescope sights have been dis- 

 cussed under the article treating of Robert Hooke, but 

 no such advantages were ever recognized by Hevelius. 

 So great was Hevelius' s reputation as an astronomer 

 that his refusal to recognize the advantage of the tele- 

 scope sights caused many astronomers to hesitate be- 

 fore accepting them as superior to the plain ; and even 

 the famous Halley, of whom we shall speak further in 

 a moment, was sufficiently in doubt over the matter 

 to pay the aged astronomer a visit to test his skill in 

 using the old-style sights. Side by side, Hevelius and 

 Halley made their observations, Hevelius with his old 

 instrument and Halley with' the new. The results 

 showed slightly in the younger man's favor, but not 

 enough to make it an entirely convincing demonstra- 

 tion. The explanation of this, however, did not lie in 

 the lack of superiority of the telescopic instrument, 

 but rather in the marvellous skill of the aged Hevelius, 

 whose dexterity almost compensated for the defect of 

 his instrument. What he might have accomplished 

 could he have been induced to adopt the telescope can 

 only be surmised. 



Halley himself was by no means a tyro in matters 

 astronomical at that time. As the only son of a 

 wealthy soap-boiler living near London, he had been 

 given a liberal education, and even before leaving col- 

 lege made such novel scientific observations as that of 

 the change in the variation of the compass. At nine- 

 teen years of age he discovered a new method of de- 

 termining the elements of the planetary orbits which 

 was a distinct improvement over the old. The year 

 following he sailed for the Island of St- Helena to make 



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