ADVERTISEMENT. of the same. Timber Measured and Valued, with other Artificers Work ; and Dialling in all its Parts, Perforined by Edward Laurence. He is to be heard of when in London at Mr Senex's at the Globe in Salisbury-Court. N. B. In Winter, and at such Times as he is not Surveying, Gen. tlemen may have their Sons Daughters Taught Accompts after a Natural, Easy and Concise Method, with the Use of the Globes and Maps, and all other useful Parts of or THE Young Surveyor's GUIDE. I Practical Geometry. Defign in this part to lay down the firft Principles of Geometry; and to do it methodically, to begin with Definitions, and the Explication of the moft ordinary Terms: To which I shall add some Maxims, wherein Natural Reafon does inftruct us; and then proceed to Geometrical Problems; and fuch Propofitions as I find convenient for this Tract, fo that a Man may be able to give a deinonftrable Account of what he does. I Geometrical Definitions. 1 A Point is that which is confidered as having no manner of Dimenfions: And as being indivifible in every refpect, the Ends or Extremities of Lines are Points.. 2 Fig.1 A Line has Length, but noBreadth, nor Thickness; of which there are two forts, viz. right or ftreight, and curve or crooked; as AB is a freight Line, BC a crooked Line. 3. Fig. 2. An Angle is the meeting of two Lines in a Point; provided the two Lines fo meeting, do not make one ftreight Line: As in the Lines AB and AC meeting together in the Point A, make an Angle BAC, which is meafur'd by an Arch of a Circle DE,defcribed from the angular Point A as a Center, and intercepted between the Lines AC, and AB, which form it an Angle, is faid to be equal to, greater or lefs than another, according as the Arch which measures it, contains as many, more, or fewer of the equal Parts into which that Circumference is fuppofed to be divided. Of which right-lined Angles there are three forts, viz. Right Angled, Acute, and Obtufe: when a Line falleth perpendicularly upon another, it maketh two right Angles, that is, neither leaneth to one fide or the other. Example Fig. 3. Let CAB be a right Line, DA perpendicular to it, that is to fay, neither leaning towards B or C, but exactly upright, then are both the Angles at A, viz. DAB and DAC right Angles, and contain in each just 90 Degrees, or the 4th part of a Circle; but if the Line DA had not been Perpendicular, but had leaned towards B, then had DAC been an Obtufe Angle, or greater then a right Angle; and DAB, an Acute Angle, or lefs then aRight Angle. 4. A Figure is that which is comprehended under one, or more Lines. 5. All Figures contained under three Sides,' are called Triangles, which Euclid divides, with refpect either to their Angles or Sides. 6. Fig. 4. An Equilateral Triangle is that which hath its three Sides equal, as the Triangle ABC. 7. Fig.5. Anifofceles Triangle, is that which hath two Sides equal: As if the two Sides AB and AC be equal, the Triangle ABC is Ifcofceles. 8. Fig. 6. AScelenum, is a Triangle having all the three Sides unequal, as GHI 9. Fig. 7. A Rectangled Triangle, is that which hath one right Angle, as DEF, 10. Fig.8. An Ambligone, or obtufe Angled Triangle, is that which hath one Obtufe Angle, H as IGH. B 2 Fig. 11. Fig. 9. An Oxygone, or Acute Angled Triangle, is that whofe Angles are all Acute, as ABC. 12. Fig 10. ASquare confifts of four equal Sides, and four right Angles, as AB. 12. A Parallelogram is a Figure that hah its two oppofite Sides B parallel. 14.Fig.11. An Oblong Rectangle,having, its oppofite Sides equal, and its Angles right, as CB, is called a long Square or Parallelogram. 15. Fig. 12. A Rhombus,is that whofe Sides are all qual, but not right Angled, as B. 16. Fig.13. ARhomboides, is that whofe op. pofite Sides and Angles are equal among themfelves; but not right Angled, as D.. t 17. Fig. 1.Parallel Lines are fuch as being in the fame Plain will never meet, keeping ftill the fame diftance one from the other; as AB and CD 18. Fig. 15. All other four fided Figures are called Trapezia: Other Figures that are contained under 5, 6, 7, or more Sides, I call Irregular, Polygones, as F is an Irregular Figure, and G is a Trapezia. Note, Such as are made by the Circumference of a Circle divided into any Nuher of equal parts, are regular Figures; having all their Sides and Angles equal, and are called from the Number of Angles they contain, as a Pentagone, Hexagone, Heptagone, Octagone, &c. Which fignifics a Figure ot 5, 6, 7 or 8 Angles or Sides, whofe |