THE GENESIS OF THE LAW OF GRAVITY 333 



Newton. 



niu&t hold good, does hold good for the circular orbit; sees also from 

 Kepler's third law that if it can be applied to the elliptical orbit as well 

 then all the planets immediately fall into that celestial harmony pre- 

 dicted by Pythagoras two millenniums before. The law holds for the 

 circle, does it not hold for the ellipse also ? We can imagine with what 

 nervous eagerness Halley argues the question with Wren and Hooke 

 and then — Heaven-inspired thought — posts him down to Cambridge to 

 consult Newton. This was in August, 1684. 



We must now rapidly review Newton's own work during the twenty 

 years following his graduation from Cambridge in 1665. From the 



