1 52 SEVENTEENTH CENTURY- PT. in. 



thus showing that gravitation explains not only the general 

 laws but even apparent exceptions. 



7. Of all bodies comets are apparently the most irregu- 

 lar, yet Newton calculated that they probably move in a 

 peculiar curve called a parabola, which is represented by the 

 section of a cone cut parallel to one of its sloping sides, and 

 since his time it has been proved that the motions of some 

 comets can be sufficiently well explained by this theory, 

 while others move in ordinary ellipses like the planets, and 

 return periodically. These and many other problems of the 

 universe Newton showed could all be referred to the action 

 of gravitation ; and he concluded his work with a grand 

 description of the mechanism of the heavens, dwelling with 

 deep reverence upon the thought of that Infinite Mind 

 which gave rise to such a wonderful and comolex machinery, 

 working in perfect order. 



Chief Works consulted, Brewster's 'Life of Newton;' * Lives of 

 Eminent Persons ' Lib. of Useful Knowledge j Airy's ' Elementary 

 Astronomy ;' Airy, ' On Gravitation,' 



