550 Mijcellanea Curiofa. 



then y AN is the Periphery defcribM by the 



Center of Gravity O (~ denoting the Ratio 



p 



of the Periphery of a Circle to the Radius) 

 and confequently the Surface generated by 



the Rotation of the Catena AD =± (— x 



P 



ANx AD=)~ x ANx AR. That is a Cir- 

 cle, the Square of whofe Radius k double 

 the Rectangle RAN, will == the Surface ge- 

 nerated by the Rotation of the Catena AD 

 about the Axis AB. After the fame man- 

 ner the Solid generated by the Rotation of 

 the Space ACHD about AC, may be fhewn 

 to be equal to a Cylinder, whofe Bads is the 

 foremention'd Circle, and its Altitude=:AC» 

 Thus alfo the Surfaces and Solids produced 

 by the Rotation of thefe Figures about any 

 other given Axis, are meafur'd. For giving 

 the Center of Gravity, they are eafily dif* 

 ODver'd* 



Of 



