4 Geometrical Inflru6iions 



Lines alfo receive their Names as they eyicdTfip^fs, pafs 

 through^ touchy or diffeci a fiiperfcial of folid Fi- 

 gure. 



Side-Lices are thofe which encompafs any Sort 

 of Figure, be it either a Square or a Polygon, as 

 does A B C D, in Def. i ?. Fig. i- 



A diagonal Line, is that which pafTeth thro' 

 the very Center of a Figure, and which begin- 

 neth and endeth at two oppofite Angles^ as E F, 

 Fig. 2. and G H, Fig. 3. pef 14.. '[^C-^l", 



The Diameter has chiefly Relation to a Line 

 that pafTes through, and touches the Center of a 

 Circle, or Oval, as does the Line I K in Figure 

 the 4th, and L M in Figure the 5 th and 6 th. In 

 an Oval there are two,, call'd the tranfverfe and 

 conjugate Diameters!' ' -^^'^'-^'^^ ^ ' '■^■'V,' : 



The Chord, or fubteiife £ine, is a Line that 

 cuts off only a fmaller . Part of a Circle from a 

 greater 5 or is more plainly like the String of a 

 Bow, which is Part of a Circle, as is the Line N 

 O, Figure the 7th •, the Bow whereof is K O P, 

 Figure the 7th ^ and the remaining Part of the 

 Circle is R, Fig. 10. 



A Line tangent, is that which toucheth any Fi- 

 gure, (whether circular or polygonar) without di- 

 viding it, and without being able to divide it, al- 

 tho' it was prolong'd never fo far, as are the Lines 



5 T in Fig 8, 9. ^ 



A Line fecant, is that which divideth, crofTeth, 

 or traverfeth any Circle, Oval, or Polygonal Fi- 

 gure, the faid Oval or other Figure remaining 

 whole •, and is plainly demonllrable by the Lines 

 T U in Fig. 9, 10. 



