PraBice Part IL 



THE FIFTEENTH PRACTIC-R 



'To defcribe.^ with the Line^ any Pdlygme whatfoe^en, 



-S u p p o s E the Regular Polygone (xi) to be of five Sides, 

 called a Pentagonci draw from the upper Angle ,(^) two 

 Lines to the. Extremities of its Bafe b and which will form 

 the Triaiigle abc. Meafure one of thefe two Lines only, 

 XV. and quote it upon -the Plan, the other being equal to it. 

 Then trace upon the Ground die Triangle CD like that 

 o£ abc upon the Paper, by the eleventh Practice ; which 

 done, take two Cords equal to the Bafe DE^ and putting 

 . their Loops over the Stakes C and bring their Extremities 

 together in the Point G. Again fliift the Cords to the Stakes 

 C and and do the fame in the Point and plant Stakes 

 at F and G. Then trace the Lines D G CF, and F£, 

 which, with the Bafe D £3 form a Regular P.enta.gone, like 

 iJiat of a in the. Plan. 



Observation;;, 



Tor tracing any other Polygone whatfoever, you niufl: 

 reduce it into Triangles, as in the foregoing Figure, and 

 transfer each of thofe Triangles one after another upon the 

 Ground, in the fame Order as they lie upon the Paper ; 

 which is to be underftood as well of Irregular Polygones, as 

 Regular i the only Difference being, that in Regular Poly- 

 gones the Triangles are equal, and in Irregular ones they 

 ^re all unqquaL 



THE SIXTEENTH PRACTICE. 



To defer ibe any Polygone whatfoever ^ with the Injirument, 



Observation. 



Thi s may be performed two different ways ; for it may 

 happen, either that the Bafe of the Polygone may be deter- 

 min'd upon the Ground, or that a fix'd Point be given where 

 its Center muftneceflarily be* 



The 



