ERRATA. Page 18. line 24. from the foot, omitted (margin) a 5. 1. 93. 3. from the top, for AC is read AG is 136. 12. from the foot, for tirangle read triangle 196. - 13. from the foot, for HBC. And read HBC, and 233. 235. - 237. 237 241. 242. 247. 266. 277. - 31. from the top, for propositions, read proposition, 14. from the foot, for fides read fide 2. from the top, for any angle read an angle 27. from the top, for DGE read DGF 25. from the foot, for of P. 4. read by P. 4. 16.&43. from the top, for Proctus read Proclus Besides these, in the 4th line of the Note to PROB. IX. in p. 320. there is ADE, instead of ADB, and Pl. I. Fig. 16. is omitted in the margin opposite to PROB. X.; and in p. 325. in the first line of the last column of the Table, there is 13, instead of 18. A straight line is that which lies evenly between its extreme points. V. A fuperficies is that which hath only length and breadth. VI. The extremities of a superficies are lines. VII. A plane fuperficies is that in which any two points being taken, the straight line between them lies wholly in that fuperficies. VIII. Omitted. IX. A plane rectilineal angle is the inclination of two straight lines to one another, which meet together, but are not in the fame straight line. N. B. When several angles are at one point B, any one • of them is expreffed by three letters, of which the letter that ' is at the vertex of the angle, that is, at the point in which ⚫ the straight lines that contain the angle meet one another, is put between the other two letters, and one of these two is • somewhere upon one of those straight lines, and the other upon the other line: Thus, the angle which is contained by ' the straight lines AB, CB is named the angle ABC, or CBA; ' that which is contained by AB, DB is named the angle ABD, 6 or DBA; and that which is contained by DB, CB is called ' the angle DBC, or CBD; but, if there be only one angle at a point, it may be expressed by a letter placed at that point; as the angle at E.' X. When a straight line standing on ano- ΧΙ. An obtuse angle is that which is greater than a right angle. XII. An acute angle is that which is less than a right angle. XIII. Omitted. A figure is that which is inclosed by one or more boundaries. XV. Any straight line drawn from the center to the circumference of a circle, is called a Radius. XVII. A diameter of a circle is a straight line drawn through the centre, and terminated both ways by the circumference. XVIII. A semicircle is the figure contained by a diameter and the part of the circumference cut off by the diameter. XIX. Omitted. xx. Rectilineal figures are those which are contained by straight lines. ΧΧΙ. Trilateral figures, or triangles, by three straight lines. XXII. Quadrilateral, by four straight lines, XXIII. Multilateral figures, or polygons, by more than four straight lines. XXIV, Of three-fided figures, an equilateral triangle is that which has three equal fides. xxv. An Isosceles triangle, is that which has only two fides equal. XXVI. A scalene triangle, is that which has three unequal fides. B2 XXVII. Book. I. A right angled triangle, is that which has a right angle. XXVIII. An obtuse angled triangle, is that which has an obtuse angle. XXIX. An acute angled triangle, is that which has three acute angles. xxx. Of four-fided figures, a square is that which has all its fides equal, and all its angles right angles. ☐☐ XXXI. An oblong, is that which has all its angles right angles, but has not all its fides equal. XXXII. A rhombus, is that which has all its fides equal, but its angles are not right angles. ᄆᄆ XXXIII. A rhomboid, is that which has its opposite sides equal to one another, but all its fides are not equal, nor its angles right angles. XXXIV. All other four-fided figures, befides these, are called Trapeziums. XXXV. Parallel straight lines, are such as are in duced ever so far both ways, do not meet. PO |