5 '^: ^Qeometrical Infiru£iwnt\ 



. ■ Of a Super fcies* " - - C 



§ 4 ASaperficies is^ that which hath Length 

 Eivd. Breadth without Depth, and according to Geo- 

 onietneians is the Production of a Line, as a Line 

 is t'he^ Pf bdiiQioii of a Point. ' ^^ ^ ^ i^n:;. 



.:.....> "^ -J /". ?.: 



-•Aiid-fhus'^we m-uft- coifceive, that the Line E F, 

 hi. Fig, ^, moving an towards G, H, doth make 

 the Sli^(^rfi(-ies E F, G H,'- which is an Extenfion 

 bounded with Lines,which hath nothing but Length 

 and Bte§dth, without Depth or Thicknefs. And 

 therefore it is the Super f cm. Surface, and Bounda- 

 ries of a Figure, if one confider it in Refpeft of its 

 Extremities, which are the Lines that clofeit, and 

 the; Face that thofe Lines make by their Motion. 



Superficiesareofreveral Kinds, not only in Ret 

 pe£t to the Inequality and the Number of Sides they 

 are compos'ibf, but alfo of the Difference of their 

 Surface, or Levels; ■ ^ 



•Thus A is a plain Superficies, 

 ■ fiiKUiCO B. a convex Superficies. 

 '' — • - C. 3. concave Superficies. 



. And the two latter are, in Gardening, very^ often 

 eail'd Amphitheatres •, fo that in this Cafe, in Re- 

 fped of their Depths and Heights, C may be a 

 concave Amphitheatre, and B a convex Amphi- 

 theatre, whilft A is a Level Lawn Parterre. &c. 

 In fine, in the Conftruclion and framing Geo- 

 metrical Figures, a Point is the Term or Bound of 

 a Line ^ th^ Line the Term,or Bound of a Superficies , 

 and the S'uperficics is the Term or Bound of a Body. 

 D. Fig. lo. Is the Plan of a large multangular 

 Cojicave, o? hollow Amphitheatre. 



