ii IntroduEtion. 



Ifhall begin firft with the Principles of Geometry, 

 and fo go on through the whole Pradice thereof, 

 as far as it relates to onr prefcnt Purpofe. And for 

 our readier Introduction to it, we are to underftand 

 that Geometry is eftablifh'd upon three Sorts of 

 Principles, viz. Defimtiovs, Axioms^, and Petitiom, 



Defnitzovs ave, firft, brief Explanations of the 

 Karnes and Forms of Lines, Superficies, ^c. that 

 are made Ufe of in all Parts of fjperficial Menfu- 

 rations and Schemes^ and this is particularly ufe- 

 ful in Gardev.lvg^ &c. to enable a Perfon to fpeak 

 properly and intelligibly. 



Axioms are felfevident Truths, which there 

 is the leaft Reafon to make ufe of, of any Thing 

 us'd in the Mathematicks : As for Inftance, that a 

 Line three Foot, is equal to one, two, three, or 

 four (feparately) of the fame Length, &c. and is 

 us'd on no other Account than to demonftrate the 

 Rationale of Addition, Subftradlion, either of Lines 

 or Numbers. 



And Petitiom are clear and intelligible Demands, 

 whereof the Execution and Practice requires not 

 any Demonftration •, thus it is eafy for the moft un- 

 learn'd, when he is bid to draw a ftreight Line, 

 or trace out a Circle, to do it, and fuch other Things 

 that are requir'd in this Diviflon. Thefe being the 

 Preliminaries of Geometrical Pradicc, let us then 

 begin on the definitive Part ^thereof. 



CHAP. 



