under Gravity, suggested by a proposition of Galileo's. 233 



Ffc. 4. 



Tig. 5. 



2-0 



(1) Jn the first instance make the displacement along OA 

 (fig. 6). Make AK = AA/ then if times along BA'O and 

 BAO are equal, on taking away the equivalent pieces KAO 

 and A'O we find the same time along BK, BA'. 



Therefore these are chords of a circle with highest point 

 at B and in the limit A'K touches the circle. 



