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CHAPTER VI. 



THE INSTRUMENTS AND AIDS OF ASTRONOMY DURING 

 THE NEWTONIAN PERIOD. 



Sect. 1. Instruments. 



1 . Oj OME instruments or other were employed at 

 O all periods of astronomical observation. But 

 it was only when observation had attained a con- 

 siderable degree of delicacy, that the exact construc- 

 tion of instruments became an object of serious 

 care. Gradually, as the possibility and the value 

 of increased exactness became manifest, it was seen 

 that everything which could improve the astrono- 

 mer's instruments was of high importance to him. 

 And hence in some cases a vast increase of size 

 and of expense was introduced ; in other cases new 

 combinations, or the result of improvements in 

 other sciences, were brought into play. Extensive 

 knowledge, intense thought, and great ingenuity, 

 were requisite in the astronomical instrument 

 maker. Instead of ranking with artisans, he be- 

 came a man of science, sharing the honour and 

 dignity of the astronomer himself. 



1. Measure of Angles. Tycho Brahe was the 

 first astronomer who acted upon a due apprecia- 

 tion of the importance of good instruments. The 



